Utilities that run where your data already is
Everyday developer and AI tools, built to run in the page rather than on a server. Ordinary tools process what you paste in your own browser and never upload it; AI tools use your own API key and talk straight from your browser to the provider you pick, never through us. Every tool names the open-source project that does the same job in code.
Popular tools
The tools whose open-source projects have the most GitHub stars.
PowerPoint to Markdown converter
Turn a .pptx into clean Markdown — one heading per slide, bullets, tables and speaker notes — ready for a RAG corpus or an LLM prompt.
#02Excel to Markdown table converter
Convert .xlsx sheets to Markdown tables and CSV in the browser, with dates and formulas resolved to their values.
#03Ollama Modelfile generator
Build an Ollama Modelfile — base model, system prompt, sampling parameters, stop sequences — plus the ollama create command.
#04Agent Skill (SKILL.md) generator
Turn a workflow description into a SKILL.md in the Agent Skills format — frontmatter, trigger description, procedure, rules and references.
#05.gitignore generator
Combine GitHub's official .gitignore templates — Node, Python, Go, Unity, macOS, JetBrains and more — into one file.
#06System prompt builder
Describe the assistant you are building and get a production system prompt: role, context, task, rules, output format and fallbacks.
#07Chat template renderer
See the exact prompt string a model receives: Llama 3, Qwen, Mistral, Gemma, Phi and DeepSeek templates, rendered from your messages.
#08Stable Diffusion image info reader
Read the prompt, negative prompt, seed, sampler and model from a generated PNG — WebUI, ComfyUI and NovelAI — and export the ComfyUI workflow.
#09RAG text chunker
Split a document into overlapping chunks exactly as LangChain's RecursiveCharacterTextSplitter would, with Chinese punctuation understood.
All tools
Sorted by the GitHub stars of each tool's open-source project · snapshot Oct 23, 2026
PowerPoint to Markdown converter
Turn a .pptx into clean Markdown — one heading per slide, bullets, tables and speaker notes — ready for a RAG corpus or an LLM prompt.
Excel to Markdown table converter
Convert .xlsx sheets to Markdown tables and CSV in the browser, with dates and formulas resolved to their values.
Ollama Modelfile generator
Build an Ollama Modelfile — base model, system prompt, sampling parameters, stop sequences — plus the ollama create command.
Agent Skill (SKILL.md) generator
Turn a workflow description into a SKILL.md in the Agent Skills format — frontmatter, trigger description, procedure, rules and references.
.gitignore generator
Combine GitHub's official .gitignore templates — Node, Python, Go, Unity, macOS, JetBrains and more — into one file.
System prompt builder
Describe the assistant you are building and get a production system prompt: role, context, task, rules, output format and fallbacks.
Chat template renderer
See the exact prompt string a model receives: Llama 3, Qwen, Mistral, Gemma, Phi and DeepSeek templates, rendered from your messages.
Stable Diffusion image info reader
Read the prompt, negative prompt, seed, sampler and model from a generated PNG — WebUI, ComfyUI and NovelAI — and export the ComfyUI workflow.
RAG text chunker
Split a document into overlapping chunks exactly as LangChain's RecursiveCharacterTextSplitter would, with Chinese punctuation understood.
LLM VRAM calculator
Estimate the GPU memory an open model needs under llama.cpp or Ollama — weights, KV cache and overhead — and which graphics cards it fits.
Browser automation script generator
Describe a task in a browser and get a browser-use agent script or a Playwright test, with stable locators and no embedded secrets.
LLM inference speed estimator
Tokens per second for a model size, quantisation and GPU — the roofline numbers vLLM and llama.cpp are bounded by.
MCP config generator
Tick the MCP servers you want and get a working config for Claude Desktop, Cursor, VS Code or Claude Code.
Mermaid diagram editor
Render Mermaid code — flowcharts, sequence, class, ER and Gantt diagrams — to an SVG you can preview and download.
AI chat with your own API key
A private ChatGPT-style chat for DeepSeek, OpenAI, Claude, Qwen, Kimi and other providers, on a key you bring.
Fine-tuning JSONL validator
Check an OpenAI chat fine-tuning file line by line before you upload it, and see its token counts and what training will bill.
Fine-tuning dataset converter
Convert training data between Alpaca, ShareGPT and OpenAI messages JSONL, with every record detected on its own.
LLM API cost calculator
Price a workload across 46 models from OpenAI, Anthropic, Google, DeepSeek, Qwen, Mistral, xAI and more, from a token count or from your actual prompt.
Multi-agent crew designer
Describe a goal and get a crewAI design: agents with roles, tasks with concrete outputs, tools, hand-offs and the YAML to run it.
PDF to images (PNG, JPG)
Render each PDF page to a PNG or JPEG at the resolution you pick, using Firefox's own PDF engine.
PDF to text extractor
Copy the text layer out of a PDF, page by page, with lines kept in reading order.
AI writing improver
Polish the grammar, clarity and flow of a draft while keeping your meaning, your facts and your language.
AI typo and grammar fixer
Fix spelling, grammar and punctuation mistakes — Chinese 的/地/得 errors included — without rewriting anything else.
AI text summarizer
Summarise an article, report or long post as one line, a short digest or a detailed breakdown, in the language you choose.
AI key insights extractor
Pull the ideas, insights, exact quotes, habits, facts and recommendations out of a talk, interview or podcast transcript.
AI meeting minutes generator
Turn a meeting transcript into decisions, action items with owners and due dates, and the questions left open.
AI research paper summarizer
Summarise an academic paper's approach and results, or get a critical review of its rigour with a letter grade.
AI flashcard and quiz maker (Anki)
Turn notes or a textbook page into Anki-ready flashcards, or into a review quiz with an answer key.
AI formal email writer
Turn rough notes, or an email you received, into a polished business email in the tone and language you need.
AI jargon explainer (glossary generator)
Get a glossary of the advanced terms in any text, each with a plain definition, an analogy and why it matters.
AI code explainer
Explain unfamiliar code, config or tool output block by block, or line by line.
AI code reviewer
Severity-ranked review findings with line references and a concrete fix for each.
AI pull request description generator
Turn a branch diff or commit list into a PR description with summary, risks and a test plan.
AI log analyzer
Paste logs or a stack trace, get the root cause, the evidence lines, and the fix.
AI Mermaid diagram generator
Describe a process or a system in words and get Mermaid code for a flowchart, sequence, class, ER or Gantt diagram.
AI PRD writer
Turn a product idea into a structured product requirements document, full or one-page, in Markdown.
AI STRIDE threat model generator
Paste a system design and get its assets, trust boundaries, data flows and a STRIDE-per-element threat list.
AI tag generator
Generate tags, keywords or GitHub topics for an article, README or post, in the case style you need.
AI user story generator
Turn a feature request into user stories with Given/When/Then acceptance criteria, as Markdown or JSON.
DNS lookup: A, AAAA, MX, TXT, NS, CNAME
Ask a public resolver what a domain actually returns, right now.
Vector similarity calculator
Cosine similarity, dot product and Euclidean distance between embedding vectors, pasted from any model or API response.
AI prompt optimizer
Turn a rough prompt into a structured one for a chat, reasoning or image model, with a list of what changed.
OCR image to text
Pull text out of screenshots, scans and photos in Chinese, English, Japanese, Korean, German or French, without uploading them.
Markdown to HTML converter
Convert Markdown to HTML with GitHub Flavored Markdown support.
Markdown to plain text cleaner
Strip the Markdown from a ChatGPT or Claude answer — asterisks, hashes, pipes, fences — and keep the text, lists and tables readable.
AI API key checker
Check whether an OpenAI, DeepSeek, Claude, Gemini or Qwen key works, which models it can see, and how fast it answers.
Unix timestamp converter
Convert epoch seconds or milliseconds to a readable date, in any zone.
Knowledge graph extractor
Extract entities and relationships from text, GraphRAG-style, as a Mermaid graph, JSON triples or tables with evidence.
OpenAI Batch API JSONL builder
Turn a list of prompts into a ready-to-upload batch file with custom_id, endpoint and body on every line.
RSA, ECDSA and Ed25519 key pair generator
Generate RSA 2048–4096, ECDSA P-256/P-384 or Ed25519 key pairs in your browser, as PEM and as OpenSSH keys.
Research report writer
Paste your sources and a question; get a cited research report, a detailed outline or an annotated source list — grounded only in what you gave.
Secret scanner for code and config
Check code, .env files and logs for API keys, tokens and private keys with rules ported from gitleaks, before you paste them anywhere.
Function calling schema generator
Paste a function signature or a description and get the JSON tool definition for OpenAI, Anthropic, MCP or plain JSON Schema.
AI video generator (text to video)
Describe a shot and get a 6- or 10-second clip, generated by MiniMax H3 and paid in credits.
Repo to prompt packer
Pack many source files into one LLM-ready document — directory tree plus every file — with token counts per file.
Prompt template filler
Fill {{variables}} in a prompt template from JSON and see the exact prompt the model will get, with what was missing and what went unused.
Image format converter
Convert between PNG, JPEG and WebP in your browser.
AI background remover
Cut the background out of a portrait with a matting model running in your browser — a transparent PNG in seconds, nothing uploaded.
AGENTS.md generator
Write the AGENTS.md, CLAUDE.md, .cursorrules or Copilot instructions file for your repository from its package.json or a short description.
AI translator (Markdown-safe)
Translate documents, READMEs and UI strings with your own AI key, keeping code blocks, links and placeholders intact.
AI CSV data analyst
Paste a CSV, ask a question in plain language, and get the findings with the pandas or SQL code that reproduces every number.
SVG optimizer
Shrink SVG files with SVGO — strip editor metadata, round coordinates, merge paths — and preview the result before downloading.
.env to JSON converter
Convert a .env file to JSON, docker -e flags or a Compose environment block, and JSON back to .env, parsed exactly as dotenv does.
AI subtitle translator
Translate SRT and VTT subtitles into 13 languages while keeping every timestamp and cue intact, optionally bilingual.
Commit message linter
Check commit messages against the Conventional Commits rules of commitlint's config-conventional, with the same rule names and messages.
JWT decoder
Read a token's header and claims, and see whether it has expired.
AI text to SQL
Ask a question in plain words, get SQL for your schema and your database dialect.
Hash generator: MD5, SHA-1, SHA-256, SHA-512
Compute a checksum of any text, in your browser, in five algorithms.
HMAC generator
Sign a message with a shared key — the key never leaves your browser.
AES encryption and decryption
AES-256-GCM with a passphrase, entirely in your browser.
Speech to text (Whisper in the browser)
Transcribe audio or video with OpenAI's Whisper running in your tab, as plain text or SRT subtitles.
Sentence similarity checker
Compare sentences by meaning with a multilingual embedding model in your browser and see a cosine-similarity matrix.
RAG answer evaluator
Score a RAG answer the ragas way — faithfulness, answer relevance, context precision and recall — with every claim checked against the context.
Password generator
Strong random passwords from the browser's cryptographic generator.
UUID generator (v4 and v7)
Generate random v4 or time-ordered v7 identifiers, in bulk.
JSON Schema validator
Check a JSON document against a JSON Schema with Ajv and see every failing path, not just the first one.
AI variable name generator
Describe it in Chinese or English, get idiomatic camelCase, snake_case and PascalCase names.
AI JSON extractor
Pull structured JSON out of emails, invoices and notes, following your schema and leaving unknown fields null.
JSON to JSON Schema generator
Infer a JSON Schema from a sample, with an OpenAI strict-mode option for structured outputs and function calling.
JSON to TypeScript interfaces
Paste an API response and get TypeScript interfaces or type aliases for it, with optional keys worked out from the data.
JSON to Go struct
Turn a JSON payload into Go structs with json tags, pointer fields for nullable values and time.Time for timestamps.
JSON to Zod schema
Generate a Zod schema from sample JSON, so the same shape is checked at runtime and inferred as a TypeScript type.
Color palette extractor
Pull the dominant colour and a palette of up to 16 colours out of any image, as HEX, RGB and HSL.
JSON to CSV converter
Turn an array of objects into a spreadsheet, and a spreadsheet back into JSON.
CSV to Markdown table
Paste a CSV export and get a Markdown table ready for a README or an issue.
AI shell command generator
Describe the task, get a bash, zsh, fish, PowerShell or cmd one-liner, with warnings on destructive ones.
HTML to Markdown for LLMs
Turn a web page's HTML into clean Markdown, with tables kept and navigation, scripts and footers removed.
PII redactor for AI prompts
Mask phone numbers, emails, ID and card numbers, IBANs, IP addresses and API keys before you paste text into ChatGPT or any other AI.
LLM SSE stream decoder
Paste a raw streaming response from OpenAI, Anthropic, Gemini or any OpenAI-compatible API and get back the full text, tool calls, reasoning and token usage.
AI README generator
Rough project notes in, a complete README.md with install, usage and options table out.
User agent parser
Turn a User-Agent string into browser, engine, OS and device.
Simplified and Traditional Chinese converter
Convert between Simplified and Traditional Chinese with OpenCC, including Taiwan and Hong Kong wording — 软件 becomes 軟體, not just 軟件.
Model size calculator
Paste a config.json and get the parameter count, weights memory at each precision and the KV cache per token.
JavaScript minifier
Minify JavaScript with terser — compression, name mangling, an ECMAScript target — and see the size before and after gzip.
AI commit message generator
Paste a git diff, get a Conventional Commits message you would actually sign off on.
JavaScript beautifier
Re-indent minified or messy JavaScript and JSON with js-beautify, choosing the indent width and brace style.
CSS formatter
Beautify minified CSS into one declaration per line, with @media blocks indented and selectors split the way you prefer.
HTML formatter
Indent HTML, including the JavaScript and CSS inside <script> and <style>, while leaving <pre> and <textarea> untouched.
Merge PDF files
Combine several PDFs into one file, in the order you choose, without uploading them.
Split PDF and extract pages
Pull out the pages you need, cut a PDF at each range, or break it into parts of N pages.
Images to PDF (JPG, PNG, WebP)
Turn photos, scans and screenshots into one PDF with A4, Letter or image-sized pages.
Open Graph and Twitter card meta tag generator
Write the title, description, canonical, Open Graph and X card tags a shared link needs, with length warnings for search results.
QR code generator
Make a QR code from a URL or text, with the error correction, size and colours you need, as PNG and SVG.
curl to code converter
Turn a curl command — including Chrome's Copy as cURL — into fetch, Python requests, Go, axios or PHP code.
JSON formatter and validator
Pretty-print, minify and validate JSON, with the depth and node count.
Number base converter
Convert between binary, octal, decimal, hex and base 36 — arbitrarily large.
AI code converter
Translate code between Python, TypeScript, Go, Rust, Java and eight other languages, idiomatically.
Word to Markdown converter
Convert a .docx file into clean Markdown or semantic HTML with mammoth.js, and see what it could not convert.
Barcode generator (Code 128, EAN-13, UPC)
Generate Code 128, EAN-13, EAN-8, UPC-A, Code 39 and ITF-14 barcodes as scalable SVG.
Image compressor
Make a photo smaller without uploading it anywhere.
AI unit test generator
Generate a runnable test file for Jest, Vitest, pytest, Go, JUnit and more from a single function.
Semver range checker
See which versions a range like ^1.2.0 or ~2.3 accepts — with npm's own node-semver, pre-releases and all.
AI writing detector and humanizer
Find the patterns that make text read as machine-written — and rewrite them out without changing a single fact.
Chinese and English spacing fixer
Add the space between Chinese and English words and numbers, and fix half-width punctuation in Chinese — without touching code or links.
Chinese to pinyin converter
Convert Chinese characters to pinyin with tone marks, tone numbers or none — with polyphones read from context, URL slugs and initials.
Base64 encoder and decoder
Encode and decode Base64, standard or URL-safe, with correct UTF-8 handling.
Image to Base64
Turn an image into a data URL you can paste into CSS or HTML.
Open source license generator
Get the full text of MIT, Apache 2.0, GPL, BSD, MPL and six other licenses, with your name and year filled in.
robots.txt generator for AI crawlers
Block AI training crawlers, or all AI bots, while choosing whether AI search engines can still cite you.
Image resizer
Scale an image to an exact width, in the page.
QR code reader from image
Decode a QR code from a screenshot or photo, without pointing a phone at your own screen.
SVG to PNG converter
Rasterise SVG icons and illustrations to PNG at 1× to 4× or an exact width, with a transparent or white background.
bcrypt hash generator and checker
Hash a password with bcrypt at the cost you choose, or check a password against an existing $2a$/$2b$/$2y$ hash.
CSS minifier
Minify CSS with CSSO, including structural optimisation that merges duplicate rules and shorthands, and see the gzipped saving.
docker run to Docker Compose converter
Convert docker run commands into a compose.yaml, one service per command, with ports, volumes, environment and GPUs.
HTML entity encoder and decoder
Escape markup-breaking characters, or turn entities back into text.
XML to JSON converter
Turn XML — RSS feeds, sitemaps, SOAP responses, Maven POMs — into JSON and back, with attributes kept under a prefix you choose.
SQL formatter
Re-indent generated or minified SQL into something reviewable.
ChatGPT export to Markdown converter
Turn conversations.json from a ChatGPT data export into clean Markdown — the branch you last saw, without system prompts or tool traffic.
llms.txt generator
Write a spec-compliant /llms.txt from your site name, a summary and a list of links grouped into sections.
JSON repair for LLM output
Fix the broken JSON language models return — single quotes, trailing commas, comments, Python literals, truncated output — and pull it out of the surrounding chatter.
Case converter
camelCase, snake_case, kebab-case, CONSTANT_CASE and more, line by line.
IP address lookup: ASN, network and country
Find out who announces an address, from which prefix, and where.
Markdown table of contents generator
Build a README table of contents whose links land on the anchors GitHub actually generates — Chinese headings and duplicates included.
XML sitemap generator
Paste a list of URLs and get a sitemaps.org-compliant sitemap.xml, split into a sitemap index past 50,000 URLs, with optional hreflang.
JSON to YAML converter
Convert JSON to YAML and YAML back to JSON, in either direction.
Punycode converter (IDN)
Convert internationalised domain names such as 中国.公司 or münchen.de to their xn-- Punycode form and back, and spot look-alike domains.
Cron expression parser
See exactly when a cron schedule will fire next.
TOTP code generator and otpauth:// builder
Current and next two-factor codes from a Base32 secret or otpauth:// URI, plus the provisioning URI and QR code for a new one.
EXIF viewer and metadata remover
See every EXIF, GPS, IPTC and XMP field hidden in a photo, and save a copy with all of it removed.
Schema.org JSON-LD generator
Turn simple key: value lines into Schema.org JSON-LD for articles, products, events, software, businesses and breadcrumbs, with Google's required fields checked.
Favicon generator (ICO, Apple touch icon, manifest)
Make favicon.ico, the Apple touch icon, Android icons and site.webmanifest from one image.
Password strength checker (zxcvbn)
Estimate how many guesses a password would really take, with crack times for four attack scenarios and the patterns that gave it away.
JSONPath tester
Try a JSONPath expression against your JSON and see every match with its exact path and JSON Pointer.
URL parser
Break a URL into protocol, host, path, query and fragment.
OpenAI token counter
Count the tokens in a prompt exactly as OpenAI's tokenizer does, and see where each token starts and ends.
Colour converter and contrast checker
Convert between HEX, RGB, HSL, HWB and OKLCH, and check contrast.
CIDR subnet calculator
Work out the network, broadcast, host range and mask of any IPv4 or IPv6 block, check containment and split it into subnets.
TOML to JSON converter
Convert TOML to JSON and JSON back to TOML — Cargo.toml, pyproject.toml and the rest — with tables and dates intact.
URL encoder and decoder
Percent-encode a query value, or a whole URL, without breaking its structure.
X.509 certificate decoder
Paste a PEM certificate, chain or CSR and read its subject, SANs, validity, key, extensions and fingerprints.
XML formatter
Indent XML by nesting depth, or collapse it back to one line.
Line deduplicator and sorter
Remove duplicate lines and sort, with natural numeric ordering.
Word and character counter
Count words, characters, lines and CJK — with a reading-time estimate.