In Browser

Go’s official tour, with every example runnable and editable in the browser. in Programming Languages →

A free curriculum and certificate with browser-based exercises. in Programming Languages →

Runnable JavaScript exercises in the browser. in Programming Languages →

A playground that runs PHP across versions with MySQL, PostgreSQL or SQLite attached. in Programming Languages →

A C tutorial you compile and run in the browser. in C, C++ & Rust →

The official space to compile and run Rust code in the browser with no install. in C, C++ & Rust →

Meta’s React-based documentation-site generator, with versioning and translation built in. in Web & Frontend →

A static-site generator written in Go that turns Markdown into websites. in Web & Frontend →

A form-driven generator that builds a ready NGINX config from domain, PHP/Node, security and performance options. in Web & Frontend →

An Obsidian plugin that publishes notes straight into a live digital garden. in Web & Frontend →

A generator that turns Markdown notes — Obsidian vaults especially — into a linked site. in Web & Frontend →

A library of ready CSS animations you can play, tweak and copy the code from. in CSS & UI Kits →

Un-minifies and formats CSS back into a readable shape. in CSS & UI Kits →

A simple tool that minifies CSS by stripping whitespace and comments, with an API too. in CSS & UI Kits →

Lea Verou’s tool to craft CSS easing curves by hand and compare them against presets live. in CSS & UI Kits →

A visual builder for CSS easing curves that covers not just cubic-bezier but linear() spring and bounce curves. in CSS & UI Kits →

Hands you a URL instantly and shows every request that arrives, headers included. in Backend, API & System Design →

A complete game development environment in the browser: code editor, sprite drawing, map editor and sound generation together. in Mobile & Desktop →

A tool that turns a simple text DSL (DBML) into shareable ER diagrams fast. in Databases →

Practise SQL with graded PostgreSQL exercises in the browser. in Databases →

Interactive SQL lessons that teach by doing in the browser; each lesson ends with an exercise where you write the query. in Databases →

An exercise set that teaches SQL by making you write queries in the browser, each section over its own dataset. in Databases →

A test site that serves subdomains with deliberately broken TLS setups (expired, self-signed, wrong host and so on). in Testing & QA →

Live-test your site across different browsers and operating systems. in Testing & QA →

A French test site that grades the TLS setup of HTTPS, SMTP and XMPP servers by cipher suite, certificate and key exchange. in Testing & QA →

A Google tool that flags bypassable rules (unsafe-inline, broad wildcards, missing directives) when you paste in a Content-Security-Policy header. in Testing & QA →

A scanner that gathers a domain's DNS, email (SPF/DKIM/DMARC), TLS and web-header security into one report. in Testing & QA →

A page that grades your browser's TLS client setup (version, cipher suites, known weaknesses). in Testing & QA →

Mozilla's in-browser checker that scores a site's headers, cookies and TLS settings against security best practice; it now lives inside MDN. in Testing & QA →

A browser-based scan that grades a site's HTTP response headers (CSP, HSTS, X-Frame-Options, Permissions-Policy and so… in Testing & QA →

Browser synthesizer that generates retro 8-bit sound effects (jumps, explosions, pickups) and exports WAV files… in Game Development →

Repository of thousands of CC BY vector icons (SVG/PNG) customizable in browser; focuses on RPG inventory, spells, and… in Game Development →

Sandboxed Python execution, image generation, file upload and custom GPTs in one window. in AI · Models & Assistants →

Anthropic’s chat app, whose long context window carries long documents and whole codebases. in AI · Models & Assistants →

A browser surface for testing prompts, setting system instructions and fiddling with temperature. in AI · Models & Assistants →

Google’s chat assistant, connecting straight into Gmail, Drive and YouTube to use your own content as source. in AI · Models & Assistants →

A web front-end for Ollama or any OpenAI-compatible endpoint, usually deployed with Docker. in AI · Models & Assistants →

Predicts structures of protein, DNA and ligand complexes with AlphaFold 3. in AI · Applied Tools →

Runs Node.js in the browser via WebContainers, so the generated full-stack app previews instantly without a server round trip. in AI · Applied Tools →

Extracts data from websites and monitors them for changes without code — you train it by clicking in the browser. in AI · Applied Tools →

Jupyter in the browser with a free T4 GPU. in AI · Applied Tools →

DALL·E-based with no barrier beyond a Microsoft account. in AI · Generative Media →

Browser-based video creation platform that generates scripts, voiceovers, stock footage scenes, and cuts from text… in AI · Generative Media →

An image generator focused on character and product imagery. in AI · Generative Media →

Cloud video generator that turns articles, scripts, and webinar recordings into captioned short-form videos; edits by… in AI · Generative Media →

Design a 3D scene in the browser and embed it straight into a page. in AI · Generative Media →

An open-source tool, born at Uber, for visualising large location datasets (millions of points, trips, grids) layer by layer in the browser. in Data Science & ML →

Interactive WebGL map clustering subreddits by shared commenters (2020-21 comments). in Data Science & ML →

A web front end for querying OpenStreetMap data through the Overpass API; it shows the result on a map, downloads it as… in Data Science & ML →

Turns a Python script into a web app in a few lines with no HTML, CSS or JavaScript. in Data Science & ML →

Builds a cron expression from a form and states in words when it will fire. in DevOps & Infrastructure →

Analyses a Dockerfile, explains what happens layer by layer and suggests improvements. in DevOps & Infrastructure →

Generates Kubernetes manifests from a form, explaining each field beside it. in DevOps & Infrastructure →

A YAML validator that surfaces indentation and quoting errors and prints the parsed document back. in DevOps & Infrastructure →

Send a test email to the temporary address it gives you and it reports SPF, DKIM and SpamAssassin scores. in Networking & Sysadmin →

A research site showing DNS records, sites sharing an IP, mail/whois data and history for a domain, IP or autonomous-system number. in Networking & Sysadmin →

Verisign's tool that validates a domain's DNSSEC chain of trust from the root down and shows where it breaks. in Networking & Sysadmin →

A quick checker for a domain's DNS and mail (MX) setup that lists errors and warnings point by point. in Networking & Sysadmin →

Looks up an IP or domain in hundreds of DNS blocklists (RBLs) at once. in Networking & Sysadmin →

An email and DNS diagnostic that runs MX, DNS, blacklist, SPF, DMARC, ping and port lookups from a single box. in Networking & Sysadmin →

A browser-based speed test needing no Flash and no app, and self-hostable on your own server. in Networking & Sysadmin →

A toolbox of dozens of DNS and domain queries in one place: reverse IP lookup, DNS history, whois, a port scanner, domain-to-IP mapping. in Networking & Sysadmin →

A checker that runs a domain's DNS setup (delegation, SOA, DNSSEC, nameserver consistency) through dozens of tests; the… in Networking & Sysadmin →

Independent static web hosting service offering 1 GB free space and an in-browser editor in the spirit of GeoCities… in Self-Hosting & Personal Cloud →

A browser tool generating CAD models from text, reaching into CAM as well. in Hardware, CAD & Embedded →

Parametric CAD entirely in the browser, working on a database rather than files, so branching and merging behave like… in Hardware, CAD & Embedded →

Simulates Arduino, ESP32 and STM32 in the browser, with virtual sensors and displays attached. in Hardware, CAD & Embedded →

Browser-based PCB schematic and layout design, tied to the JLCPCB parts library. in Electrical & Electronics →

A simulator that lets you draw a circuit in the browser and shows current and voltage as a live animation. in Electrical & Electronics →

Browser 3D design plus circuit and Arduino simulation — an electronics playground for beginners. in Electrical & Electronics →

Connects HeyCyan glasses to a browser over Web Bluetooth. in Smart Glasses & Wearables →

Privacy-respecting metasearch engine that proxies results from Google, Bing, Brave, and Yandex without tracking or… in Privacy & Personal Security →

Scores how much your ad blocker actually stops, broken out by ads, trackers, social buttons and cookie notices. in Privacy & Personal Security →

A suite of tests, one tab each, showing what your browser leaks (IP/WebRTC, canvas and font fingerprints, JavaScript, geolocation, client hints). in Privacy & Personal Security →

Estimates how long a password would take to brute-force, computed in the browser so the password is never sent. in Privacy & Personal Security →

A pastebin the server cannot read: the text is encrypted in the browser and the key lives in the URL fragment, which is never sent. in Privacy & Personal Security →

A form that generates the /.well-known/security.txt file (RFC 9116) telling security researchers where to report a… in Privacy & Personal Security →

A profiler that identifies the CMS, analytics, hosting and JavaScript technologies a site uses from its address. in Offence, Defence & OSINT →

Passive reconnaissance for a domain: subdomains, DNS records and a host map, with no scan of the target itself. in Offence, Defence & OSINT →

Offensive Security's searchable archive of published exploits and vulnerability write-ups, indexed by CVE. in Offence, Defence & OSINT →

Visualisation of global wind, ocean-current and air-pollution forecasts on a live globe. in Science & Academia →

Shows the real sky for your location in the browser, with time you can wind forward to see planetary positions. in Science & Academia →

A free online graphing calculator producing fast, shareable interactive graphs. in Mathematics →

Dynamic maths software that links geometry, algebra and calculus live. in Mathematics →

Draw a graph in the browser and run shortest path, connectivity and flow algorithms on it. in Mathematics →

An equation solver that shows the worked steps to a solution, derivatives, integrals and limits included. in Mathematics →

A browser-based laboratory for designing and simulating quantum optics experiments. in Quantum Computing →

Supply-chain search engine indexing US customs sea-shipment bills of lading to reveal which overseas factories and… in Economics →

Runs portfolio backtesting, Monte Carlo simulation and factor analysis in the browser. in Finance, Markets & Crypto →

A catalogue of ready-to-use colour palettes curated by community votes. in UI Design, Colour & Type →

An AI generator that learns from photos and art to suggest harmonious colour palettes. in UI Design, Colour & Type →

The most widely used tool for interface design, with Dev Mode handing measurements and tokens to developers. in UI Design, Colour & Type →

Previews a palette live on a real UI. Unlike palette generators, you see colours in context — text, buttons, background — rather than as swatches. in UI Design, Colour & Type →

A calculator that turns a chosen ratio into a visual typographic scale with ready CSS. in UI Design, Colour & Type →

Drop in a font file and it reports everything inside: character set, OpenType features, variable axes — plus the CSS that switches each of them on. in UI Design, Colour & Type →

Enter a foreground and a background colour and it gives the contrast ratio and whether it passes WCAG AA/AAA for normal… in UI Design, Colour & Type →

A browser tool that generates blobs, waves and layered SVG background shapes. in Icons, Photos & Illustration →

A free tool for flowcharts and diagrams. Unlike Lucidchart it is entirely free and lets you keep diagrams in your own repository or cloud. in Media, Files & Diagrams →

A hand-drawn-style whiteboard. Looking deliberately rough is functional rather than stylistic — it stops a draft… in Media, Files & Diagrams →

Merge, split, compress and convert. Unlike desktop PDF tools it needs no installation; be careful with sensitive… in Media, Files & Diagrams →

An online tool for diagrams and flowcharts with team collaboration. in Media, Files & Diagrams →

Browser-based piano-roll sequencer for composing multi-track melodies and exporting MIDI files with zero setup; built… in Media, Files & Diagrams →

Open-source, browser-based video editor that processes media locally on your device without uploading files; serves as… in Media, Files & Diagrams →

A video editor running in the browser with the footage staying on device — an alternative that needs no installation and no upload to a cloud service. in Media, Files & Diagrams →

An image editor in the browser that opens PSD, XCF, Sketch and XD files with their layers intact. in Media, Files & Diagrams →

A pixel art and sprite animation editor in the browser. in Media, Files & Diagrams →

A tool for drawing pixel art in the browser, with drawings shareable with the community. in Media, Files & Diagrams →

Cloud-based image-editing tools that run in the browser. in Media, Files & Diagrams →

Generates Sankey flow diagrams from text input, for energy, budget or funnel flows. in Media, Files & Diagrams →

Image compression with a side-by-side comparison, running MozJPEG, WebP and AVIF encoders in the browser through WebAssembly. in Media, Files & Diagrams →

A subtitle editor in the browser for opening .srt and .vtt files and fixing timings and text. in Media, Files & Diagrams →

Edits SVG path data (the d attribute) visually while listing the commands one by one. in Media, Files & Diagrams →

Shrinks PNG and JPEG files through selective quantisation: drag, drop, no settings. in Media, Files & Diagrams →

Converts a bitmap image into vector art. Against Illustrator’s trace, its edge detection is noticeably cleaner — it is… in Media, Files & Diagrams →

An editor that produces high-resolution favicons from images. in Media, Files & Diagrams →

A backend-focused curriculum with in-browser exercises. in Learning & Roadmaps →

Short video then in-browser coding with instant grading. in Learning & Roadmaps →

In-browser lessons across 15+ languages. Because everything runs in the browser instead of a local setup, it removes… in Practice & Challenges →

SQL and data science interview questions with real queries run and checked in the browser. in Practice & Challenges →

A complete free curriculum with in-browser exercises and free certificates. in Practice & Challenges →

Draw the symbol you want with the mouse and it returns the matching LaTeX command and the package it needs. in Cheat Sheets & Quick Reference →

Pick what you are trying to do from menus and it composes the right Git command. in Cheat Sheets & Quick Reference →

A catalogue of commonly needed regular expressions (email, phone, dates, IP addresses), each with a diagram, an explanation and a place to try it. in Cheat Sheets & Quick Reference →

An IDE framework that runs on the desktop and in the browser and takes VS Code extensions. in Editors, IDEs & Terminals →

An open-source, in-browser Markdown editor with live preview and export. in Editors, IDEs & Terminals →

A collaborative LaTeX editor in the browser; compilation runs on the server and thousands of journal and thesis templates are ready. in Editors, IDEs & Terminals →

A place to try monospaced coding fonts side by side on real code. in Editors, IDEs & Terminals →

A new typesetting language meant as an alternative to LaTeX, and its online editor; the compiler is open source (Rust)… in Editors, IDEs & Terminals →

A gallery previewing VS Code themes on real code. in Editors, IDEs & Terminals →

Write, run and share C# and .NET code in the browser. in Online Playgrounds & Compilers →

A browser playground for HTML, CSS and JavaScript. in Online Playgrounds & Compilers →

A collaborative editor for technical interviews with live coding (many languages). in Online Playgrounds & Compilers →

Runs projects with full npm dependencies in the browser. in Online Playgrounds & Compilers →

Real-time collaborative code editing in the browser with no install or account. in Online Playgrounds & Compilers →

Puts the generated assembly beside your source, with optimisation level and compiler version switchable so you see the difference immediately. in Online Playgrounds & Compilers →

Compiles and runs 60+ languages in the browser and accepts an input stream. in Online Playgrounds & Compilers →

A JSFiddle-like scratchpad with a live output panel; showing console output on the same screen is handy when debugging. in Online Playgrounds & Compilers →

The oldest and lightest way to test a small JavaScript snippet. in Online Playgrounds & Compilers →

An open-source online compiler. Unlike closed services such as Ideone you can self-host its engine — the project people… in Online Playgrounds & Compilers →

An in-browser playground to try HTML, CSS and JS with live preview. in Online Playgrounds & Compilers →

An online IDE supporting many languages, with no install. in Online Playgrounds & Compilers →

An experimental tool that converts code written in one language into others — C#, Java, Python, JavaScript. in Online Playgrounds & Compilers →

An online IDE that compiles C and many other languages in the browser. in Online Playgrounds & Compilers →

A JavaScript and TypeScript playground that runs as you type and accepts npm packages. in Online Playgrounds & Compilers →

A collaborative cloud IDE that writes and runs dozens of languages in the browser and can deploy a project in one click. in Online Playgrounds & Compilers →

Runs Node.js in the browser through WebContainers. in Online Playgrounds & Compilers →

Runs dozens of C++ compiler versions side by side. in Online Playgrounds & Compilers →

Formats JavaScript, HTML and CSS and unpacks minified code. in Converters, Formatters & Checkers →

A collection of formatting, validation and conversion tools covering JSON, XML, YAML, SQL and Base64. in Converters, Formatters & Checkers →

Translates a cron expression into plain language as you type and shows the next run times. in Converters, Formatters & Checkers →

GCHQ's in-browser data transformation tool: base64, hex, crypto, compression and parsing chained as a drag-and-drop 'recipe'. in Converters, Formatters & Checkers →

A visual regex tester that draws the expression as a state diagram, covering JavaScript, Python and PCRE. in Converters, Formatters & Checkers →

A diff tool for text, images, PDFs and folders. in Converters, Formatters & Checkers →

A collection of developer tools: a REST client, a SQLite browser, XML and JSON validators, regex testing. in Converters, Formatters & Checkers →

A browser tool for drawing points, lines and polygons on a map while editing the GeoJSON in a side panel; it exports to… in Converters, Formatters & Checkers →

A two-way converter between decimal and IEEE-754 floating point, with individual bits toggleable. in Converters, Formatters & Checkers →

A Portuguese-language site bundling small text utilities — reversing, counting, converting and more. in Converters, Formatters & Checkers →

Eighty-odd developer utilities on one page: hashes, JWT decoding, cron expressions, UUIDs, colour conversion. in Converters, Formatters & Checkers →

A tool that minifies JavaScript in the browser to shrink its size. in Converters, Formatters & Checkers →

Draws JSON as a node graph rather than a tree, so nested structures are visible at a glance. in Converters, Formatters & Checkers →

A browser tool to inspect and edit JSON in tree and text views. in Converters, Formatters & Checkers →

A simple tool that alphabetically sorts and formats JSON keys. in Converters, Formatters & Checkers →

A JSON validator and formatter that tells you which line failed and why. in Converters, Formatters & Checkers →

A collection of developer converters, formatters and generators. in Converters, Formatters & Checkers →

A browser tool that simplifies map data in shapefile, GeoJSON, TopoJSON or CSV and converts between those formats; the… in Converters, Formatters & Checkers →

A simple password generator with adjustable length and character sets. in Converters, Formatters & Checkers →

Explains an expression token by token, and its debugger shows exactly where a match breaks down. in Converters, Formatters & Checkers →

Turns a JavaScript regular expression into a railroad diagram, with groups, alternatives and repetition drawn as boxes and arrows. in Converters, Formatters & Checkers →

A regex tester and an alternative to regex101, with a simpler interface and a community library of patterns. in Converters, Formatters & Checkers →

Draws JavaScript regular expressions as railroad diagrams. in Converters, Formatters & Checkers →

A collection of online debugging and network tools for developers and sysadmins. in Converters, Formatters & Checkers →

A form that generates the CAA DNS record, which controls which certificate authorities may issue certificates for your… in Converters, Formatters & Checkers →

You build a table cell by cell in a visual grid and it emits LaTeX, HTML, Markdown, plain text or MediaWiki, and accepts pasted CSV. in Converters, Formatters & Checkers →

Crawls a site and builds the sitemap.xml file for search engines. in Converters, Formatters & Checkers →

A list of useful web apps that work without login. in Productivity & Everyday Tools →

A list of userscripts that enhance your browsing experience. in Productivity & Everyday Tools →

A browser extension that finds the largest/original version of an image or video from its shrunken form. in Productivity & Everyday Tools →

A tool for making branded link buttons for LittleLink pages. in Productivity & Everyday Tools →

Browser-to-browser file transfer between devices on the same network, connected directly over WebRTC. in Productivity & Everyday Tools →

Browser extension that brings Vim-style keyboard navigation (j/k scrolling, f link hints, tab search) to the web… in Productivity & Everyday Tools →

Makes repository content navigable, running in the browser with no server. in Lists, Directories & Discovery →

Discovery dashboard for trending open-source GitHub repositories filtered by language and timeframe; offers faster… in Lists, Directories & Discovery →

Combines hackerspaces, fablabs and makerspaces from SpaceAPI, Fablab.io and the Hackerspaces wiki on one map, with a heatmap of open/closed status. in Lists, Directories & Discovery →