Free Online Tools

Merge PDF

Combine multiple PDF files into one unified document. All processing happens in your browser.

Image Compression

Fast, secure, and efficient image compression. Supports JPG, PNG, and WebP formats with compression rates up to 80%.

JSON Formatter

Validate, format, and minify JSON in your browser, with tree and properties views.

Developer Tools

ASCII Art Generator

Convert text to ASCII art banners (200+ figlet fonts) or turn images into ASCII character art. All processing happens in your browser.

ASCII Code Table

Complete 7-bit ASCII table (0-127) with octal, hex, decimal, binary, character, abbreviation and description columns. Live search, format converter and one-click copy.

Base64 Text

Encode and decode text with standard or URL-safe Base64, entirely in your browser.

Chinese Converter

Convert Chinese text between Simplified, Standard Traditional, Hong Kong Cantonese and Taiwan Traditional.

Chmod Calculator

Pick the read / write / execute flags for owner (u), group (g) and public (o). The tool computes the three-digit octal mode, the rwx symbolic string and a copy-ready chmod command.

CRC Calculator

Calculate CRC-8, CRC-16, and CRC-32 checksums for text or hex input. Supports the most common algorithms used in networking, file formats, and embedded protocols.

Crontab Generator

Visually build and decode crontab expressions with live English description, symbol reference, and one-click presets. Supports 5-field (standard) and 6-field (with seconds) variants.

Encoding & Crypto Toolkit

Hash, encrypt, and encode data right in your browser — MD5, SHA, AES-256-GCM, Unicode escaping, and HMAC. Base64 has its own dedicated tool.

Data Format Converter

Convert data between XML, JSON, TOML, CSV and YAML right in your browser, with automatic source-format detection.

Date Format Converter

Enter any date — Unix timestamp, ISO 8601, common strings, RFC, or database formats — and instantly see conversions across all formats.

Emoji Picker

Browse, search and copy Unicode emoji by category. Click any card to copy the unicode escape string to your clipboard.

Flow Diagram

Browser-based flow diagram editor powered by LogicFlow. Supports five standard flowchart shapes — rectangle, circle, diamond, parallelogram, and comment box — plus polyline edges, undo/redo, JSON and PNG import/export. Everything runs locally — your diagrams never leave your device.

JSON Formatter

Validate, format, and minify JSON in your browser, with tree and properties views.

JWT Decoder

Decode and inspect JSON Web Tokens — header, payload, claims, and expiry — entirely in your browser. Nothing is sent to any server.

Markdown Editor

Write Markdown with real-time preview, Mermaid diagrams, synchronized TOC, and export to .md / .docx / .pdf.

Morse Code Translator

Translate text to and from International Morse code. Listen to the result with adjustable speed (5-30 WPM), and copy the output for further use.

MQTT Tester

Free online MQTT client that runs entirely in your browser. Connect to any MQTT broker over WebSocket (ws:// or wss://), subscribe to topics, publish messages and inspect traffic in real time — no installation required.

OpenSSL rand

Generate cryptographically secure random strings using the browser's CSPRNG (equivalent to `openssl rand`). Supports hex, base64, passwords and more.

Password Generator

Generate strong, random passwords with customizable length and character sets.

Regex Tester

Test regular expressions with custom flags and inspect matches and capture groups in real time.

Scientific Calculator

Free online calculator with Standard, Scientific and Programmer modes. Arithmetic with parentheses and percent, trigonometry, powers, roots, logarithms and factorials, plus BIN/OCT/DEC/HEX conversion and bitwise operations with 8–64 bit signed or unsigned integers. All calculations run locally in your browser.

Snowflake ID Generator

Generate Twitter-style 64-bit Snowflake IDs with configurable epoch and worker ID. Batch generation supported.

Special Symbols

Browse, search and copy special symbols by category — math, currency, arrows, Greek letters, chess pieces, fancy game ID characters and more. Click any card to copy.

SQLite Viewer

Open any SQLite database file in your browser. Inspect tables, browse data, and run read-only SELECT queries without installing anything.

Text Diff

Compare two texts side by side with line numbers and inline highlights, with options to ignore line ending and control character differences.

Unit Converter

Convert between common units of length, weight, temperature, and data storage.

URL Encoder / Decoder

Encode or decode URLs and form data, with control over how spaces are represented.

UUID Generator

Generate UUIDs (Universally Unique Identifiers) in multiple versions and formats. All generation happens locally in your browser.

XML Online Viewer

View, beautify, minify, validate XML online and convert to JSON / CSV. Three-pane layout (input | actions | output), auto-format, file upload, URL load, syntax-aware tree view, one-click download.

Image Tools

App Icon Generator

Design an app icon with Material Symbols clipart, text or your own image, then download production-ready Android, iOS and Web icon packs.

Barcode Generator

Generate CODE128, EAN-13, EAN-8, UPC, CODE39, and ITF-14 barcodes with custom size, color, and font. Single mode with live preview or batch mode (one-per-line or file import) with ZIP download.

Color Converter

Convert colors between HEX, RGB, RGBA, HSL and CMYK with live preview, and browse standard web colors.

Color Palette Generator

Extract a brand color palette from any image and export a ready-to-use Design.md, CSS variables, and PNG swatch — fully local, no upload.

Favicon Generator

Convert PNG, JPEG, GIF, BMP and more to a multi-resolution ICO favicon. Choose icon sizes and 8-bit or 32-bit color depth.

Banner Maker

Generate funny recognition banners (锦旗) for coworkers, friends, and teammates — perfect for gag gifts, retirement send-offs, and inside jokes. 6 visual styles + 5 'funny worker' preset phrases, all rendered locally.

Certificate Maker

Generate funny certificates with real background templates. 5 styles, customizable name line, body text, and footer with position sliders. All processing is local.

Image ↔ Base64

Convert images to Base64 strings or decode Base64 back to images.

Image Compression

Fast, secure, and efficient image compression. Supports JPG, PNG, and WebP formats with compression rates up to 80%.

Image Converter

Convert PNG/JPG/WebP images and adjust quality in your browser.

Image Crop

Crop, rotate, and flip images in your browser. Supports PNG, JPG, and WebP formats.

Image Resizer

Resize PNG/JPG images to exact pixel dimensions right in your browser.

Watermark Remover

Paint over watermarks, logos, or date stamps and erase them with local inpainting. Supports PNG, JPG, and WebP — images never leave your browser.

Maze Generator

Generate perfect mazes with DFS or Prim algorithms in your browser. Customize size, cell size, wall thickness and colors, mark start and end, show the solved path, animate the generation, and export as PNG or SVG.

PH Style Logo Generator

Generate PH / YouTube / GitHub / Bilibili style logos in your browser with pure Canvas 2D. Customize text, colors, fonts and gradients, then export as transparent PNG, JPG or SVG.

Perler Beads Generator

Upload an image and generate a perler-bead / fuse-bead / pixel-art pattern with adjustable grid size, color count, and transparent background. Matches the MARD standard 221-color palette and exports a printable PNG and a CSV bead list.

QR Code Decoder

Upload a QR code image and decode its contents instantly in your browser. Supports text, URLs, vCards, Wi-Fi credentials, and more.

QR Code Generator

Generate QR codes from text or URLs with custom dot styles, finder patterns, colors, gradients, embedded logo and text, then download as PNG.

Seal Maker

Generate traditional round seal (印章) designs with custom main text, center symbol, bottom text, colors, noise, and double borders. Perfect for design mockups and entertainment.

SVG to PNG

Render SVG files or code to PNG images at any size using canvas.

Video Tools

Screen Recorder

Free online screen recorder: screen-only, camera-only, or camera overlay on screen with draggable circular PiP. System audio + mic mixing, 480p-4K. Pure browser MediaRecorder — no install, no upload.

Video Converter

Convert videos between MP4, WebM, MKV, AVI, MOV and GIF online. Adjust quality, frame rate, resolution and audio. 100% in-browser, no upload.

Video Merger

Merge 2-5 video clips (MP4, AVI, MOV, MKV, WebM and more) into one file online. Mixed formats and resolutions are normalized automatically. 100% in-browser, no upload.

Video Resizer

Resize MP4, AVI, MOV, MKV or WebM videos to 360p, 480p, 720p, 1080p, 1440p, 4K or custom dimensions online. Convert between MP4, WebM, MKV, AVI and MOV. 100% in-browser, no upload.

Video to GIF

Convert MP4, WebM, MOV or MKV video clips to animated GIF online. Custom start time, duration, width and frame rate. 100% in-browser, no upload.

Video Trimmer

Losslessly trim MP4, AVI, MOV, MKV, WEBM video online: pick start/end points to keep or cut a segment with original quality intact. Plus rotate, flip, crop, resize, speed change and looping. 100% in-browser, no upload.

Video Watermark

Add a PNG, JPG or WebP image watermark to MP4, WebM, MOV or MKV videos online. Drag to position, adjust size, opacity and display period. 100% in-browser, no upload.

Video Watermark Remover

Remove static watermarks, corner logos and date timestamps from MP4, WebM, MOV and MKV videos. Drag a box over the watermark and the area is rebuilt from surrounding pixels. Processed entirely in your browser — videos are never uploaded.

Audio Tools

Audio Compressor

Compress audio files online. Reduce MP3, WAV, FLAC and more into smaller MP3, M4A or Opus with adjustable bitrate, channels, and sample rate. 100% in-browser, no upload.

Audio Converter

Convert audio between MP3, WAV, OGG, AC3, FLAC, Opus, PCM, M4A and AAC online. Adjust bitrate, sample rate and channels. 100% in-browser, no upload.

Audio Merge

Mix 2-5 audio clips with per-clip trim, fade in/out, and insert-at time. Overlap or arrange sequentially with full control. 100% in-browser, no upload.

Audio Splice

Splice 2-5 audio files end-to-end into one. Mix MP3, WAV, M4A, OGG and more with automatic format normalization. Reorder clips with up/down buttons. 100% in-browser, no upload.

Audio to Text

Transcribe audio files to text, subtitles and documents in 99+ languages. Powered by OpenAI Whisper, runs 100% in your browser via WebAssembly — audio never leaves your device.

Audio Trimmer

Trim audio with a visual waveform. Cut, speed up, slow down, change volume, or loop any MP3, WAV, M4A, OGG and more — right in your browser. 100% client-side, no upload.

Video to Audio

Extract the audio track from any video (MP4, MOV, MKV, WEBM and more) and save as MP3, M4A, WAV, OGG or Opus. 100% in-browser via FFmpeg, no upload, no re-encode of video pixels.

PDF Tools

Image to PDF

Combine JPG, PNG and WebP images into a single PDF. Drag to reorder, choose page size and orientation. All processing happens in your browser.

Compress PDF

Reduce PDF file size by re-encoding images as JPEG and removing metadata. All processing happens in your browser.

Delete PDF Pages

Select pages to remove from a PDF by checking their thumbnails. All processing happens in your browser.

Merge PDF

Combine multiple PDF files into one unified document. All processing happens in your browser.

Reorder PDF Pages

Change the order of pages in a PDF by dragging thumbnails or using arrow buttons. All processing happens in your browser.

Rotate PDF

Rotate all or selected pages of a PDF by 90°, 180° or 270°. All processing happens in your browser.

Split PDF

Split a PDF into multiple files by page range or every N pages. All processing happens in your browser.

PDF to Image

Convert PDF pages to PNG or JPEG images in your browser. Render all pages and download them as a ZIP archive or individually.

Office Tools

Bar Chart

The bar chart displays categorical data as vertical bars whose lengths are proportional to the values they represent, anchored to a baseline at zero — the most familiar chart for comparing discrete items across a fixed set of labels. The form is widely credited to William Playfair's 1786 *Commercial and Political Atlas*, the same volume that introduced the line chart and the area chart; the L-shaped axis pair with the categorical axis at the bottom has become a near-universal visual convention. Choose a bar chart when you want to compare a small number of categories — typically fewer than twenty — whose values are measured on a single scale. Monthly sales by product, regional population, and survey counts are classic fits. Reach for a line chart instead when the horizontal axis is continuous time, and a pie or donut only when you also need to show part-to-whole at a single moment. The chart only works when the zero baseline is visible; truncating the y-axis exaggerates small differences and is the most common way readers are misled. Sort bars by value when the category order is not inherently meaningful, and avoid three-dimensional effects that distort length perception. When the categories have long names or there are more than ten of them, rotate to a horizontal bar chart for legibility. All rendering happens in your browser — your data never leaves your device and is never uploaded to any server. Export the finished chart as PNG (2× pixel ratio) or CSV (raw data), choose from five colour palettes, switch between light and dark themes, and toggle a watermark for shared images.

Candlestick Chart

Create candlestick (OHLC) charts online for free. Visualize stock prices with open / high / low / close. Visual editor, PNG / CSV export.

Donut Chart

Create donut / ring charts online for free. Visual data editor, color palettes, PNG / CSV export. Perfect for percentage breakdowns and part-to-whole data.

Funnel Chart

Create funnel charts online for free. Visualize conversion stages, sales pipelines, and drop-offs. Visual editor, PNG / CSV export.

Gantt Chart

Create Gantt charts online for free. Per-task assignee, 4-level priority with theme colors, drag to reschedule, resize to adjust duration, switch granularity (hour/day/week/month), export as PNG.

Gauge Chart

Create gauge charts online for free. Display a single value on a dial meter with configurable min/max. Visual data editor, PNG export.

Line Chart

Create line charts online for free to visualize trends over time. Visual data editor, color palettes, PNG / CSV export.

Mind Map

Create mind maps online for free. Editable radial tree diagrams with click-to-rename, add children, and remove nodes. 5 color themes, watermark, title, PNG / TSV export.

Org Chart

Create org charts online for free. Visualize reporting structures and team hierarchies with left-to-right orthogonal tree. Visual editor, PNG / TSV export.

Radar Chart

Create radar (spider) charts online for free. Compare multiple metrics across multiple subjects. Visual editor, PNG / CSV export.

Nightingale Rose Chart

Create Nightingale rose charts (polar area diagrams) online for free. Compare values across categories with varying radii. Visual editor, PNG / CSV export.

Sankey Diagram

Create Sankey diagrams online for free. Visualize flows, transfers, and multi-stage processes. Visual editor, PNG / CSV export.

Scatter Chart

Create scatter charts online for free. Plot individual data points to spot outliers and patterns. Visual editor, PNG / CSV export.

Stacked Area Chart

Create stacked area charts online for free. Visualize trends across multiple categories. Visual data editor, PNG / CSV export.

Stacked Bar Chart

Create stacked bar charts online for free. Show composition across categories with multiple series. Visual data editor, PNG / CSV export.

Tree Map

Create tree maps online for free. Display hierarchical data with nested rectangles sized by value. Visual editor, PNG / CSV export.

Word Cloud

Create word clouds (tag clouds) online for free. Visualize text frequency and importance with beautiful, color-coded word arrangements. PNG / CSV export.

SEO Tools

Broken Link Scanner

Find all broken links in a page. Paste HTML, then the tool batch-checks every <a href> link (server-side, 10 in parallel, up to 100 per batch) and flags 4xx/5xx/network errors.

Core Web Vitals Checker

A reference manual for Google Core Web Vitals (LCP, CLS, INP, FCP, TTFB) with official 75th-percentile thresholds, common causes, and improvement tips. To measure CWV for any URL, use the recommended tools below.

Crawler Fetch Simulator

Simulate a URL fetch as Googlebot Desktop, Googlebot Smartphone, Bingbot, or a generic browser via User-Agent. See the returned status, response time, body size, content-type, and HTML metadata (title, description, OG, Twitter, JSON-LD, headings).

HTTPS Certificate Checker

Best-effort browser-side HTTPS / TLS inspection. Verifies the connection succeeds (no certificate error), checks HSTS presence, and audits subresource protocols (HTTP vs HTTPS) for mixed content.

Meta Tag Generator

Generate SEO-friendly meta tags for your web pages in real time. Copy the HTML snippet and paste it into the head section of your HTML.

NoFollow Link Checker

Parse HTML and classify every <a href> link by rel attribute (dofollow / nofollow / sponsored / ugc). Shows internal vs external split, counts each rel type, and per-link table.

Open Graph & Twitter Card Generator

Generate Open Graph (og:) and Twitter Card meta tags for any page. Fill the form, copy the HTML, and paste into your page's <head>. Preview how Twitter and Facebook will display your link card.

Redirect Chain Checker

Trace an HTTP redirect chain hop-by-hop. See each 3xx status, the Location header, the next URL, total hops, and total time. Detects loops and reads <link rel="canonical"> from the final HTML.

Robots.txt Generator

Create a robots.txt file to guide search engine crawlers. Define allowed and disallowed paths, crawl delay, and sitemap location.

SEO Comprehensive Audit

Multi-aspect SEO audit aggregator. Enter a URL to fetch the page and run 15 weighted SEO checks — HTTP status, HTTPS, meta tags, social cards, structured data, robots.txt, sitemap.xml, and more — producing a 0-100 score with per-check pass/warn/fail status and recommendations.

Schema.org JSON-LD Generator

Generate Schema.org JSON-LD structured data for the 4 most common types: Article, Product, FAQ, HowTo. Field-by-field form, live JSON-LD output, copy with one click. Validates JSON before showing.

SERP Title & Description Preview

Preview how your page title and meta description appear in Google search results. Shows character counts, pixel-width truncation at Google's 580px / 920px limits, and warns when titles or descriptions exceed recommended lengths.

XML Sitemap Generator

Turn a list of URLs into a search-engine-friendly XML sitemap. Download the file and submit it to Google or Bing.

URL HTTP Status Checker

Check the HTTP status code and response headers of any public URL. See Content-Type, Cache-Control, X-Robots-Tag, Server, the final URL after redirects, and response time in milliseconds.

GEO Tools

AI-Bot Crawler Simulator

Simulate how 7 major AI crawlers (GPTBot, ClaudeBot, Google-Extended, PerplexityBot, Bytespider, etc.) would interpret your page. Paste HTML + robots.txt and see which bots can access your content, what they extract, and which metadata they pick up.

AI-Sitemap Generator

Generate AI-friendly sitemap files in one click. Create llms.txt, ai.txt, sitemap.xml, and robots.txt with proper AI crawler rules for Anthropic, GPTBot, ClaudeBot, and other LLM crawlers.

AI Citation Snippet Previewer

Preview how your content might be cited by AI assistants. Generate 6 formats (definition, listicle, how-to, FAQ, comparison, verbatim excerpt) and see the actual snippet + citation that an LLM would emit. Use this to judge whether your content is 'quotable'.

Entity Metadata Detector

Extract entities from your page's structured data (Schema.org JSON-LD, OpenGraph, Microdata) and check whether each entity has the fields an AI assistant needs to reliably cite. Shows completeness score per entity, missing fields, and Knowledge Graph sameAs links.

GEO Comprehensive Audit

Run 8 GEO dimensions in one audit: AI-bot access, sitemap/discovery files, page-noise ratio, structured data, entity metadata, citability, RAG friendliness, and HTML quality. Returns a weighted overall score (0-100) plus per-dimension reports.

GEO Schema Generator & Validator

Description

LLM Citability Scorer

Score your content 0-100 based on how likely an LLM is to cite it. Evaluates 7 dimensions: structured data, definitional sentences, source citations, entity metadata, FAQ/heading structure, content length, and lists. Use this to spot gaps before publishing.

Page Noise Stripper

Strip away navigation, footer, ads, scripts, styles, comments, and other chrome from a page's HTML — leaving only the content an AI assistant would actually consume. Useful for previewing what an LLM ingests from your page, or for cleaning up before chunking/RAG.

RAG Semantic Chunk Simulator

Simulate how a RAG (Retrieval-Augmented Generation) pipeline would chunk your content. Try 4 strategies (fixed-size, sentence, paragraph, heading-based) with adjustable chunk size and overlap. See the actual chunks an embedding model would receive — and judge whether your content is 'RAG-friendly'.

Robots.txt AI-Bot Compliance Checker

Audit your robots.txt against 18 AI crawlers (GPTBot, ClaudeBot, Google-Extended, PerplexityBot, Bytespider, etc.). See which bots are explicitly allowed, explicitly blocked, or fall through to the default — and generate a recommended AI-friendly robots.txt configuration.

Puzzle Tools

Diamond Solitaire

Free offline Diamond Solitaire (Peg Solitaire / Brainvita / Kongming Chess) on a 7x7 cross-shaped board with 33 holes. Five starting-position variants (easy / beginner / classic / advanced / expert) for different difficulty. Click-select then click-target to jump pegs orthogonally; aim to leave 1 peg at the center ('genius'). 100% local browser play, no upload, no account.

2048

Free online 2048 game: slide the tiles and merge matching numbers to reach the target tile. Five target difficulties (128 to 2048), a timer and the site-wide rank system (Master/Pro/College/Grade School/Preschool). Play with keyboard or touch.

24 Points

Free online 24 point game: draw 4 playing cards and make 24 with addition, subtraction, multiplication and division. A counts as 1, J/Q/K count as 10. Every deal is guaranteed solvable, with hints, solutions, a timer and score stats.

Gomoku

Play classic 15×15 Gomoku against a local AI with five difficulty levels, scoring, ranks, Renju forbidden-move rules and anime-style big-move callouts.

Grid Minesweeper

Free offline grid-based logic puzzle. 3 presets (9×9 / 16×16 / 30×16) plus custom boards, first-click safe mine generation, flood-fill reveal, dual-button chord, and right-click flagging. 100% local browser play, no upload, no account.

Light Up

Place light bulbs on white cells to illuminate every white cell. No two bulbs may see each other.

Lights Out

Click a cell to toggle it and its 4 orth neighbors. Turn all lights off to win.

Memory Match

Free online memory match game: flip cards to find matching pairs and clear the board. Five board sizes (12 to 30 cards), a timer and the site-wide rank system (Master/Pro/College/Grade School/Preschool).

n-back Memory

Train your working memory with the classic n-back task. Eight difficulty levels from 1-back to 8-back.

Number Huarong

Play the classic sliding-tile puzzle (a.k.a. 15-puzzle / N-Puzzle / Huarong Dao) in your browser with three grid sizes — 3×3 (beginner, 8-puzzle), 4×4 (standard 15-puzzle, the most popular competition size), and 5×5 (advanced 24-puzzle). Solved-state scramble is reverse-random-walk guaranteed to be 100% solvable. Includes a five-rank rating system based on the rolling average of your last 20 game scores. All processing is local in your browser — nothing is uploaded.

Number Sequence Memory

Free online number-sequence memory training: a chimp-task variant. Watch N digits flash at random grid positions, then click them in ascending order from memory. Starts at 4 digits, +1 per level, ends after 3 failures.

Reversi

Play standard 8x8 Reversi against a local AI with five difficulty levels, legal move hints, side switching, rank scoring, and match history.

Schulte Grid

Free online Schulte grid attention training: tap the numbers in order from 1 to N². Five sizes (3×3 Starter to 7×7 Expert), a 0.1s timer, click-rhythm attention analysis and the site-wide rank system (Master/Pro/College/Grade School/Preschool).

Sequence Memory

100% free offline Simon-style memory game. 3 difficulty presets (3×3 / 4×4 / 5×5), start at length 3/4/5 and grow by 1 each round. Watch the lights, repeat the order. No account, no upload, no leaderboard, no ads — just local brain training in your browser.

Skyscrapers

Free offline Skyscrapers (高楼 / 摩天楼) puzzle: N×N Latin-square grid (4×4 / 5×5 / 6×6 / 7×7 / 8×8) with 4-side visibility clues mapped to AGENTS §14 difficulty 1-5. Each row and column contains 1..N exactly once; taller towers hide shorter ones behind them. Generator runs locally with cache, so even 8×8 puzzles open instantly on second play. 100% local browser play, no upload, no account, no leaderboard.

Stroop Test

Measure cognitive interference with the classic Stroop color-word task. Five difficulty tiers across four colors.

Sudoku

Play free online Sudoku in your browser: classic 9×9, plus 6×6 and 4×4 mini boards for kids and beginners. Multiple difficulty levels with guaranteed unique solutions — no guessing ever needed. Notes, conflict highlighting, undo, hints, timer, quick input, and PNG/PDF printing.

Tic-Tac-Toe

Play Tic-Tac-Toe (noughts and crosses) against the computer or with a friend on the same device. Three AI difficulty levels (random, 1-ply lookahead, perfect minimax) include a site-wide difficulty rating system with five ranks from preschool to master. All processing happens locally in your browser — no data is uploaded to any server.

Practical Tools

File Compress & Extract

Free browser-side archive tool. Compress multiple files into ZIP / GZIP / TAR / TAR.GZ with optional password, or extract ZIP / 7Z / RAR / BZ2 archives. Files never leave your device.

Barcode Generator

Generate CODE128, EAN-13, EAN-8, UPC, CODE39, and ITF-14 barcodes with custom size, color, and font. Single mode with live preview or batch mode (one-per-line or file import) with ZIP download.

Blood Type Calculator

Calculate the probability of a child's ABO blood type based on parents' phenotypes. Reference only — for educational use.

BMI Calculator

Free online BMI (Body Mass Index) calculator. Supports metric (cm / kg) and imperial (ft + in / lb) units with real-time WHO category classification and healthy weight range.

Schedule Planner

Plan tasks and events on a monthly calendar, support cross-day items, priority colors, and export to PNG, PDF, or XLSX.

Color Blindness Test

Screen your color vision across 4 categories (control / protan / deutan / tritan) with 12 procedurally generated Ishihara-style plates. Get a 6-class screening result with severity and confidence, plus practical advice.

Color Palette Generator

Extract a brand color palette from any image and export a ready-to-use Design.md, CSS variables, and PNG swatch — fully local, no upload.

CRC Calculator

Calculate CRC-8, CRC-16, and CRC-32 checksums for text or hex input. Supports the most common algorithms used in networking, file formats, and embedded protocols.

Banner Maker

Certificate Maker

Generate funny certificates with real background templates. 5 styles, customizable name line, body text, and footer with position sliders. All processing is local.

Morse Code Translator

Translate text to and from International Morse code. Listen to the result with adjustable speed (5-30 WPM), and copy the output for further use.

Perler Beads Generator

QR Code Decoder

Upload a QR code image and decode its contents instantly in your browser. Supports text, URLs, vCards, Wi-Fi credentials, and more.

Resume Generator

Create a professional resume in your browser. Choose from 5 templates, fill in your details, and export to PNG, PDF, or Word.

Screen Test

27 fullscreen test patterns for verifying monitor quality: dead pixels, backlight bleed, signal interference, focus, contrast, color gradients, saturation, and OLED burn-in. All patterns render locally, no upload.

Seal Maker

Generate traditional round seal (印章) designs with custom main text, center symbol, bottom text, colors, noise, and double borders. Perfect for design mockups and entertainment.

SQLite Viewer

Open any SQLite database file in your browser. Inspect tables, browse data, and run read-only SELECT queries without installing anything.

Trip Itinerary

Plan a multi-day trip in a clean table: day labels work as relative “Day 1…n” or real dates, each day holds time, activity, cost and notes, and the result exports to print-ready PDF, PNG or Excel.

Study Tools

Bopomofo Chart

Interactive Bopomofo (ㄅㄆㄇㄈ) chart with color-coded initials, medials, and finals (37 symbols total). Click any symbol to read its pronunciation guide and pinyin cross-reference.

Chinese Pinyin Chart

Interactive Chinese pinyin table with 21 initials, 38 finals, 4 tones, and 16 whole-read syllables. Click any cell to read its pronunciation guide.

Chinese Tracing

Generate printable handwriting practice worksheets in 田字格 / 米字格 / 回宫格 styles. Enter Chinese text, pick a grid style, customize color & columns, then print.

Class Schedule Maker

Create a class timetable online: AM/PM sessions, default times, customizable font, text color and background fill, and one-click export to print-ready A4 PDF, Excel or PNG.

Banner Maker

Certificate Maker

Generate funny certificates with real background templates. 5 styles, customizable name line, body text, and footer with position sliders. All processing is local.

Grid Paper

Generate essay paper (with word-count ticks), math vertical-alignment paper, math draft paper, or grid/graph/dot/hex paper for printing. Configure page size and grid parameters with live preview, export as PNG/SVG, and print directly.

Japanese Kana Chart

Interactive Japanese kana chart (五十音図) with the standard 11×5 layout: 10 gojuon rows + moraic nasal. Click any kana to read the pronunciation guide and hear it spoken via Web Speech API.

Korean Hangul Chart

Interactive Korean Hangul chart with 140 syllables (14 consonants × 10 vowels). Click any cell to see syllable composition, IPA, and example words.

Math Problem Generator

Generate daily arithmetic worksheets aligned with the Chinese K-6 elementary curriculum (grades 1-6): each grade draws problems round-robin from its own type distribution, with adjustable difficulty and time targets. Note: the underlying curriculum is the Chinese national K1-6 standard (人教版), even though the UI is localised.

Periodic Table

Interactive periodic table of chemical elements with color-coded categories. Click any element to see atomic number, mass, electron configuration, and a short description. Export the chart as PNG or PDF.

Pomodoro Clock

Pomodoro Technique timer with 4 preset duration schemes (25/5/20, 20/5/15, 30/7/30, 40/10/30), task-name logging, daily history, pause/resume support, and optional beep alerts.

Random Name Picker

Upload a student list (CSV — Excel users can save as CSV first). One click randomly picks a name from the roster with a dice-shake animation. Supports repeats, attendance marking, and absent list export.

Typing Practice

Practice typing English words from K-12 and university vocabulary banks. Choose a difficulty, listen-dictation or image-hint mode, and track your WPM and accuracy.

categories.cheatsheets

adb

Quick reference for the Android Debug Bridge CLI: device discovery, install / uninstall, logcat, shell, push / pull, port forwarding, and wireless debugging — with common options and practical examples.

avd manager

Quick reference for the Android Virtual Device (avdmanager / emulator) CLI: create / edit / delete AVDs, list system images, headless emulator launches, snapshot management, and network forwarding — with common options and practical examples.

aws cli

Quick reference for the AWS Command Line Interface: configure credentials, IAM identity, EC2 / Lambda / S3 / DynamoDB / IAM, profiles, SSO, and pagination / output formatting — with common options and practical examples.

azure cli

Quick reference for the Azure CLI (az): authentication, subscription / resource management, VM / AKS / Storage / App Service / Key Vault, query formatting, and CI-friendly workflows — with common options and practical examples.

cmd

Quick reference for the classic Windows Command Prompt (cmd.exe): file/dir operations, text search, system info, networking and batch scripting — with common options and practical examples.

conda

Quick reference for Conda CLI commands: environment management, package install / search, channels, lockfiles, configuration, and cleanup — with common options and practical examples.

curl

Quick reference for curl: HTTP verbs, headers, authentication, JSON, forms, uploads, downloads, redirects, debugging, retries, and connection controls — with common options and practical examples.

docker

Quick reference for everyday Docker CLI commands: container lifecycle, image builds, logs / exec, networking, volumes, Compose, registry and housekeeping — with common options and practical examples.

gcloud

Quick reference for gcloud (Google Cloud CLI), gsutil, and bq commands: authentication, project / IAM, Compute / GKE / BigQuery / Cloud Storage, config, and Cloud Build / Deploy — with common options and practical examples.

git

Quick reference for the most useful Git commands: init, clone, branch, merge, rebase, reset, stash, remote operations and history inspection, with common options and practical examples.

gradle

Quick reference for the Gradle CLI: project tasks, dependency management, multi-project builds, wrapper, configuration cache, and build scan — with common options and practical examples.

kubectl

Quick reference for kubectl, the Kubernetes command-line client: contexts, get/describe, apply, logs/exec, rollout, scaling and debugging — with common options and practical examples.

linux shell

Quick reference for everyday Linux / macOS shell commands: file operations, text processing, permissions, processes, networking, archive and storage — with common options and practical examples.

maven

Quick reference for Maven CLI commands: project lifecycle phases, dependency management, plugins, multi-module reactors, repository deployment, and debugging — with common options and practical examples.

mongodb

Quick reference for mongosh: connect, CRUD, query operators, aggregation pipeline, indexes, replica sets, users and dump/restore — with the most common shell patterns and practical examples.

mvnd

Quick reference for Maven Daemon (mvnd) — a long-lived JVM wrapper around `mvn` that keeps a background daemon to skip JVM startup on every build. Same CLI as Maven, plus daemon management commands.

mysql

Quick reference for MySQL / MariaDB: client commands, DDL/DML statements, joins/aggregates, indexes, transactions and backup/restore — with common options and practical examples.

npm

Quick reference for everyday npm CLI commands: init / install / add / remove / update / scripts / run / publish / audit, plus lockfile, registry, and cache management — with common options and practical examples.

npx

Quick reference for npx commands: run one-off package binaries, scaffold projects, manage the npx cache, pin versions, and avoid pitfalls with interactive CLIs — with common options and practical examples.

pip

Quick reference for the pip package installer CLI: install / uninstall / inspect packages, virtual environments, requirements files, configuration, and index management — with common options and practical examples.

pnpm

Quick reference for pnpm: install / add / remove / update, scripts, workspaces, store & cache and config — focused on the GitHub-site pnpm repo workflow, with options and practical examples.

postgresql

Quick reference for PostgreSQL: psql client commands, DDL/DML statements, joins/aggregates, indexes, transactions and backup/restore — with common options and practical examples.

powershell

Quick reference for PowerShell cmdlets: discovery, file/system, pipeline filtering and selection, networking, remote sessions and modules — with common parameters and practical examples.

pytest

Quick reference for the pytest CLI: test discovery, selection, fixtures, markers, parallelism, parametrize, and coverage integration — with common options and practical examples.

redis cli

Quick reference for redis-cli: connection & info, key/string commands, hashes, lists, sets, sorted sets, streams, pub/sub, server management, persistence & replication and diagnostics — with common options and practical examples.

ssh

Quick reference for OpenSSH: connections, key management, the user config file, file transfer (scp/rsync/sshfs), port forwarding and jump hosts — with common options and practical examples.

svn

Quick reference for Subversion (SVN) commands: checkout, update, commit, branch/tag, merge, history inspection and repository administration, with common options and practical examples.

uv

Quick reference for the uv CLI: Python project init, dependency management, virtual environments, lockfile resolution, tool runners, and self-update — with common options and practical examples.

vim

Quick reference for Vim / Neovim: modes, cursor motion, editing, search & replace, multi-file navigation, registers / macros and visual-block edits — with short examples for the most common moves.

vite

Quick reference for Vite CLI commands: dev server, build, preview, dependency pre-bundling, plugin management, environment variables, and project inspection — with common options and practical examples.

volta

Quick reference for everyday Volta commands: install Node / npm / Yarn / pnpm toolchains, pin per-project versions, manage global packages, and troubleshoot Volta itself — with common options and practical examples.

yarn

Quick reference for everyday Yarn CLI commands (both Yarn Classic 1.x and Yarn Berry 2/3/4): install / add / remove / run / workspaces, lockfile, Plug'n'Play, and Berry configuration — with common options and practical examples.

Language Cheatsheet

C

A concise, self-contained reference for C (C11/C17): syntax, pointers, memory, strings, structs, and file I/O, plus threads, sockets, regex, time, processes, and build/debug essentials. Covers around 80% of day-to-day needs.

C++

A concise C++17/20 cheatsheet covering syntax, the standard library, classes, templates, and the most common idioms — roughly 80% of everyday scenarios.

C#

C# 12 (with .NET 8) syntax, OOP, LINQ, and the most commonly used standard library—a cheatsheet covering about 80% of everyday scenarios.

Dart

A cheatsheet for Dart 3 syntax, type system, async and the most-used standard libraries — covering ~80% of daily work.

Go

A Go 1.22 reference for syntax, types, goroutines, and the most-used standard library packages — about 80% of day-to-day needs.

Java

A concise cheatsheet for Java 17+ syntax, OOP, collections, and the most commonly used standard library APIs, covering roughly 80% of daily scenarios.

JavaScript

A cheatsheet for modern JavaScript (ES2022) syntax, the standard library, and the most common DOM / Node helpers — covering about 80% of everyday scenarios.

Kotlin

A Kotlin 2.0 syntax, null safety, coroutines, and most-used standard library cheatsheet covering about 80% of everyday scenarios.

Perl

A cheatsheet for Perl 5.38 syntax, regular expressions, references, and the most common built-in functions — covering ~80% of daily use cases.

PHP

A concise quick-reference for PHP 8.3 syntax, types, arrays and the most-used standard library — covers ~80% of everyday needs.

Python

A concise reference for modern Python 3 (3.11+) syntax, built-in types, and the most-used standard library modules — covers about 80% of everyday scenarios.

R

A cheatsheet for R 4.4 syntax, data structures and the most-used base R / tidyverse functions, covering about 80% of everyday scenarios.

Rust

A concise Rust 2021 cheatsheet covering syntax, ownership, error handling and the most common std APIs — about 80% of everyday scenarios.

Scratch

Scratch 3 block-based programming cheatsheet: variables, lists, clones, broadcasts and the nine block categories — covers beginners' games, animations and storytelling.

Swift

A cheatsheet for Swift 5.9 syntax, value types, protocols, and the most-used standard library — covering about 80% of everyday scenarios.

TypeScript

A quick reference for TypeScript 5 syntax, the type system, and the most common idioms — covers about 80% of day-to-day usage.

Keyboard Shortcuts

After Effects

Adobe After Effects has been the standard for motion graphics, visual effects, and compositing since 1993, used in nearly every film, TV show, and YouTube video with motion graphics. After Effects shortcuts are tightly coupled to the timeline (J/K to step between keyframes, Space to preview) and to layer properties (P/S/R for position/scale/rotation, Alt+click to add expressions). This reference card covers the most-used 80+ shortcuts across 6 functional areas: Common, Tools, Keyframes & timeline, Layers & compositions, Expressions & scripting, View & preview. All entries are transcribed from Adobe's official After Effects documentation. How to use - Pick your platform (Windows / macOS) at the top. - Search any feature name or shortcut text. - Click any row's Copy button to grab the key string. - Export PNG (2400×1140 landscape) for a wallpaper; PDF for a single A4 landscape page. Tips - F9 = Easy Ease — instantly apply smooth interpolation to selected keyframes. Single most useful animation shortcut. - Alt+click on a property's stopwatch icon adds an expression. Type `wiggle(2, 30)` and preview for a classic camera shake. - J / K step between keyframes on the selected property; . and , do the same in the Composition panel. - U (in timeline) shows only modified properties of the selected layer — a great audit tool for complex comps. - Space to preview, 0 on numpad for full RAM preview, Ctrl+Alt+B to set work area bounds. Why this separate from premiere-shortcuts? After Effects is motion graphics / compositing (keyframe animation + effects), Premiere Pro is video editing (timeline cuts + transitions). Different tools, different shortcut ecosystems. Splitting keeps each focused.

AutoCAD

A printable reference for the most-used Autodesk AutoCAD keyboard shortcuts (Windows + macOS, command aliases are identical). Covers common file commands, single-letter command aliases, modify commands, selection & inquiry, annotation & dimensions, view & zoom, and layers & properties.

Blender

A printable reference for the most-used Blender 3D keyboard shortcuts (Windows + macOS + Linux — keys are nearly identical across all 3). Covers common file commands, general editing (transforms), tools (3D View), selection modes, view & navigation, animation & timeline, and rendering.

Chrome DevTools

A printable reference for the most-used Google Chrome browser and Chrome DevTools keyboard shortcuts. Covers common commands, tabs & windows, address bar & search, page navigation, DevTools panels, and DevTools debugging.

Excel

A printable reference for the most-used Microsoft Excel keyboard shortcuts. Covers common commands, data entry, selection & navigation, formulas, formatting, rows & columns, worksheets, and PivotTables. Top toolbar switches between Windows and Mac keys — the same shortcut shows the correct keys for each platform. Click any row's Copy button to grab the keys.

Figma

A printable reference for the most-used Figma keyboard shortcuts (Web / Mac / Windows). Covers common commands, tools, selection & transform, text, shapes & frames, components & auto layout, and view & export. Keys are mostly identical across platforms (Figma uses Cmd on Mac, Ctrl on Windows).

Illustrator

A printable reference for the most-used Adobe Illustrator keyboard shortcuts (Windows + macOS). Covers common commands, tools, selection & objects, drawing & editing, text, and view & artboard.

IntelliJ

A printable reference for the most-used JetBrains IntelliJ IDEA keyboard shortcuts. Covers common actions, navigation & search, editing, selection, refactoring, run & debug, Git version control, and tool windows. Top toolbar switches between Windows, Linux, and macOS keys — the same shortcut shows the correct keys for each platform.

Lightroom

A printable reference for the most-used Adobe Lightroom Classic keyboard shortcuts (Windows + macOS). Covers common commands, library (import & grid), develop, masking & local adjustments, export & metadata, and view & navigation.

macOS

A printable reference for the most-used macOS 13+ keyboard shortcuts. Covers system-wide shortcuts, menus, window management, screenshots, Finder, text editing, Safari, and accessibility. Click any row's Copy button to grab the key combo, or export to PDF / PNG for a printable reference card.

Notion

A printable reference for the most-used Notion keyboard shortcuts (Web + Mac + Windows desktop). Covers common commands, editing & blocks, selection & navigation, formatting & markdown, links & references, comments & collaboration, view & theme.

Photoshop

A printable reference for the most-used Adobe Photoshop keyboard shortcuts (Windows + macOS). Covers common commands, tools, selection, layers, edit/transform, view/canvas, and brush/fill/color.

PowerPoint

A printable reference for the most-used Microsoft PowerPoint keyboard shortcuts. Covers common commands, slideshows, slide editing, text formatting, objects & shapes, tables & charts, and review/comments. Top toolbar switches between Windows and macOS keys.

Premiere Pro

A printable reference for the most-used Adobe Premiere Pro keyboard shortcuts (Windows + macOS). Covers common commands, timeline editing, markers & navigation, effects & transitions, captions & titles, and export & project.

VS Code

A printable reference for the most-used Visual Studio Code keyboard shortcuts, with one-click platform switching between Windows, macOS, and Linux. Every shortcut is grouped by function (General, Editing, Navigation, Debug…) so you can find what you need in seconds.

Windows

A printable reference for the most-used Windows 10/11 keyboard shortcuts. Covers system, file explorer, window management, screenshots, virtual desktops, accessibility, and common text editing. Click any row's Copy button to grab the key combo for the current platform, or export to PDF / PNG for a printable reference card.

Word

A printable reference for the most-used Microsoft Word keyboard shortcuts. Covers common commands, text editing, selection, formatting, paragraphs, document navigation, tables, and review/comments. Top toolbar switches between Windows and Mac keys — the same shortcut shows the correct keys for each platform.

WPS Office

A printable reference for the most-used WPS Office keyboard shortcuts (Writer / Spreadsheet / Presentation). Covers common commands, text formatting, tables, spreadsheet editing, slideshow, view, and cloud collaboration. WPS shortcuts are mostly compatible with Microsoft Office — plus a few WPS-specific keys for cloud save and PDF export.

Command Cheatsheets

View all cheatsheets

VCS

git

Quick reference for the most useful Git commands: init, clone, branch, merge, rebase, reset, stash, remote operations and history inspection, with common options and practical examples.

31 commands

Git 2.30+

VCS

svn

Quick reference for Subversion (SVN) commands: checkout, update, commit, branch/tag, merge, history inspection and repository administration, with common options and practical examples.

28 commands

SVN 1.10+

SHELL

linux shell

Quick reference for everyday Linux / macOS shell commands: file operations, text processing, permissions, processes, networking, archive and storage — with common options and practical examples.

40 commands

bash 5+ / POSIX 2017

SHELL

powershell

Quick reference for PowerShell cmdlets: discovery, file/system, pipeline filtering and selection, networking, remote sessions and modules — with common parameters and practical examples.

34 commands

PowerShell 7+

SHELL

cmd

Quick reference for the classic Windows Command Prompt (cmd.exe): file/dir operations, text search, system info, networking and batch scripting — with common options and practical examples.

40 commands

Windows cmd.exe 10+

postgresql

Quick reference for PostgreSQL: psql client commands, DDL/DML statements, joins/aggregates, indexes, transactions and backup/restore — with common options and practical examples.

36 commands

PostgreSQL 14+

mysql

Quick reference for MySQL / MariaDB: client commands, DDL/DML statements, joins/aggregates, indexes, transactions and backup/restore — with common options and practical examples.

38 commands

MySQL 8.0+

redis cli

42 commands

Redis 6.2+

mongodb

Quick reference for mongosh: connect, CRUD, query operators, aggregation pipeline, indexes, replica sets, users and dump/restore — with the most common shell patterns and practical examples.

30 commands

MongoDB 6.0+ / mongosh 1.6+

NET

ssh

Quick reference for OpenSSH: connections, key management, the user config file, file transfer (scp/rsync/sshfs), port forwarding and jump hosts — with common options and practical examples.

26 commands

OpenSSH 9.0+

NET

curl

Quick reference for curl: HTTP verbs, headers, authentication, JSON, forms, uploads, downloads, redirects, debugging, retries, and connection controls — with common options and practical examples.

30 commands

curl 7.88+

EDIT

vim

Quick reference for Vim / Neovim: modes, cursor motion, editing, search & replace, multi-file navigation, registers / macros and visual-block edits — with short examples for the most common moves.

37 commands

Vim 9 / Neovim 0.9+

volta

25 commands

Volta 1.x

npm

34 commands

npm 10+

yarn

33 commands

Yarn 1.x (classic) / Yarn 4 (berry)

pnpm

Quick reference for pnpm: install / add / remove / update, scripts, workspaces, store & cache and config — focused on the GitHub-site pnpm repo workflow, with options and practical examples.

31 commands

pnpm 9+

npx

25 commands

npx 10+ (shipped with npm)

vite

30 commands

Vite 5+

JAVA

maven

34 commands

Maven 3.9+

JAVA

mvnd

29 commands

Maven Daemon 1.0+

JAVA

gradle

Quick reference for the Gradle CLI: project tasks, dependency management, multi-project builds, wrapper, configuration cache, and build scan — with common options and practical examples.

30 commands

Gradle 8+

AND

adb

33 commands

Android Platform Tools 34+

AND

avd manager

34 commands

AVD Manager 34+

uv

Quick reference for the uv CLI: Python project init, dependency management, virtual environments, lockfile resolution, tool runners, and self-update — with common options and practical examples.

39 commands

uv 0.4+

conda

Quick reference for Conda CLI commands: environment management, package install / search, channels, lockfiles, configuration, and cleanup — with common options and practical examples.

40 commands

Conda 24+

pip

37 commands

pip 24+

pytest

Quick reference for the pytest CLI: test discovery, selection, fixtures, markers, parallelism, parametrize, and coverage integration — with common options and practical examples.

34 commands

pytest 8+

aws cli

40 commands

AWS CLI v2

azure cli

43 commands

Azure CLI 2.60+

gcloud

48 commands

gcloud 480+

kubectl

Quick reference for kubectl, the Kubernetes command-line client: contexts, get/describe, apply, logs/exec, rollout, scaling and debugging — with common options and practical examples.

40 commands

kubectl 1.28+