NETROOM
Excalidraw is a virtual whiteboard for diagrams in a hand-drawn style: architecture sketches, user flows, wireframes and anything else that is quicker to draw than to describe. It runs in the browser with no sign-up - open a tab and start drawing. There are libraries of ready-made shapes, export to PNG and SVG, collaboration over a link with end-to-end encrypted rooms, and files you can keep locally or in your own storage. Open source, with a self-hosted option for teams.
Squoosh compresses images in the browser: drop a file in, pick a format and a quality, download the result. A slider puts the original and the compressed version side by side, so you can see exactly where artefacts start and stop just before them. It handles a range of formats, each with its own controls - from a single quality dial to the codec's own parameters. Nothing is uploaded: the work happens on your device, and it runs offline once installed as an app. Built by Google Chrome Labs, open source, no sign-up.
The Cyber Swiss Army Knife, built by the UK's GCHQ. You chain operations into a "recipe" and push text or a file through it: base64, XOR, AES, DES, Blowfish, hashes, hexdumps, X.509 and IPv6 parsing, archive extraction, charset conversion. Everything runs in the browser - nothing is sent to a server, and you can download the page and use it offline. Apache 2.0 plus Crown Copyright. Invaluable for picking apart logs, dumps and suspicious payloads.
A Swiss army knife for PDFs in the browser, running on your own server: merge and split, rotate, compress, convert to and from office formats, OCR, sign, redact, and chain operations through a REST API - over fifty tools in all. The point is that files never reach someone else's cloud. One docker run gets you going, and a desktop client and Kubernetes charts exist too. It is open core: the base is open source while some capabilities sit behind paid Server and Enterprise plans.
The VS Code you already use, opened at vscode.dev with nothing to install. It browses and edits repositories on GitHub and Azure Repos, opens local folders through the browser's file access, installs browser-compatible extensions and syncs your settings from the desktop app. Good for reading someone else's code from a borrowed machine or a tablet. No terminal and no debugger - the sandbox can't run code - and language support is partial. Free; signing in is optional.
AFFiNE is a workspace where a document and a whiteboard are the same thing: pull a block of text onto an edgeless canvas, then turn that canvas into a presentation. It holds pages, wikis, database tables, a board mode and an AI helper for outlines and mind maps. Data lives on your device and syncs from there rather than the other way round, so it works offline. Install it as an app or self-host it with Docker. Open source under MIT - Notion and Miro in one tool you can take with you.
A desktop app that uses AI to sort cluttered folders — Downloads, external drives, NAS shares — into categories and subcategories and to suggest readable file names. It renames images by their content through a local visual model (IMG_2048.jpg becomes clouds_over_lake.jpg), documents by their text, and audio and video by their tags. Nothing moves until you approve it, and the last run can be undone. Models can be local (Gemma 3 4B, your own GGUF) or remote — OpenAI, Gemini, any OpenAI-compatible API; with a local one your files never leave the machine. Windows, macOS and Linux, AGPL-3.0.
ASCIIFlow draws diagrams out of characters: boxes, arrows, lines and labels that add up to a picture living inside a code comment, a README or an email. No images, no attachments - the result copies out as plain text and looks the same anywhere a monospaced font does. Paste an existing diagram back in and keep editing it. Everything runs in the browser, nothing is uploaded, no sign-up. A desktop build is available too. Open source under MIT.
ASM Editor is an assembly IDE that runs in the browser: write the code, set a breakpoint, step through it and watch the registers and memory change. It covers M68K, MIPS, RISC-V and x86, each with its own register set and stack tracing. Differences between steps are highlighted, so you see not just the current state but what the last instruction actually did. Nothing to install - no toolchain, no emulator. Free and open source.
AST Explorer shows what a parser makes of your code: source on the left, tree on the right, and clicking a node highlights the text it came from. It carries dozens of parsers - JavaScript, TypeScript, CSS, HTML, GraphQL, SQL, YAML and others - each with its own options. A transform tab lets you write a Babel plugin, a jscodeshift codemod or an ESLint rule right there and see the result as you type. A link carries the code and the settings with it. Open source under MIT.
An extension for Chrome, Safari and Edge, plus an app for macOS and Windows, that swaps private data out of a prompt before it reaches the chatbot. It works through a digital twin: "Peter Parker" arrives at the model as "Julio Schmidt", an address becomes a different address, and the answer is unwrapped back to the real values on your side. It covers names, emails, phone numbers, URLs, SSN and Tax ID numbers, bank details and addresses; the vendor says detection runs on the device, using the compact Rampart model together with deterministic rules. Free for personal use, seven languages. Companies get the paid AgentCloak Server. The product is closed source, so the claims cannot be checked in code.
An educational space for talking with AI «echoes» of thirty historical figures - philosophers, scientists, artists, mystics. Six formats: four learning chapters (story, wisdom, prism, quest), free conversation, and a council where several figures argue with each other. Over three hundred stories and dialogues, all voiced in English and German. Thirty messages a day without an account, unlimited with your own OpenRouter key, or run it locally in Docker. Open source under AGPL-3.0, built by a German nonprofit.
Algorithm Visualizer shows what happens inside an algorithm: sorting, graph traversal, search - every step drawn next to the code performing it. Code on the left, animation on the right, and you can see which line moves which element. Take a ready example from the library or write your own and watch it the same way. It earns its keep when you are explaining an algorithm to someone else, or working out why yours behaves differently than expected. Runs in the browser, open source under MIT.
A React library of micro-interactions: transitions, button animations, and a dozen-plus card layouts - arc, carousel, stack. Built on Motion, with components copied into your project as source rather than pulled in at runtime, so nothing extra lands in the bundle. Ships a CLI and a shadcn/ui-style registry, plus light and dark themes. Needs React 18+, Tailwind, and Motion. Handy when you want the UI to feel alive without hand-rolling every animation. Open source, MIT.
Aperi'Solve takes an image apart looking for what is hidden in it: bit layers per channel, colour remaps, and a dozen and a half analysers run in parallel - zsteg, steghide, outguess, exiftool, binwalk and more. The result shows which tool found what, with extracted files to download, metadata and geotags alongside. It is the usual first stop for steganography CTF tasks, and it works just as well when you are simply curious what is baked into a file. Comes with a wiki on the methods. Open source, self-hostable via Docker.
Search the Apple App Store straight from a browser - no iTunes, no Apple device needed. Type a name or a developer and see what turns up in the store. Useful for a quick check on whether an app is published, a look at its listing, or a peek at what neighbours in the niche are shipping. It is a static client-side app built with Vite: no signup, works on the hosted address, and you can build it yourself and drop it on any web server. Open source under MIT.
Seven free, open-source Rust programs from the ArtCraft team, meant as replacements for professional editors: photo (PhotoCraft), vector (VectorCraft), video (FilmCraft), a photo library with raw development (LightCraft), PDF (PdfCraft), motion graphics (EffectCraft) and page layout (DesignCraft). They are native apps for macOS, Windows and Linux rather than browser wrappers, and six of the seven also open in the browser through WebAssembly. Files stay on your machine, layouts and shortcuts are familiar, and the programs can be driven through a CLI and an MCP server, so by an AI agent too. For now only PhotoCraft and PdfCraft are in early alpha; the rest are in development.
AudioMass is an audio editor in the browser: trim, join, level the volume, cross-fade, apply an effect, record a take from the microphone. A multitrack mode lets you drag clips around, overlap them with crossfades and bounce the result down to a single file. The waveform is drawn in full, so silence and clipping are visible at a glance. Nothing is uploaded - the processing happens on your machine, which suits both a rough podcast cut and a quick fix to a recording. Open source.
A generator for atmospheric background gradients: layers with blend modes, blur, opacity, and an optional grain overlay - all tuned live in the browser, with layers you can add, reorder, and undo. Take the result as code (CSS, Tailwind, CSS variables, or CSS-in-JS) or as a PNG or SVG image. One button assembles a prompt for ChatGPT, Claude, or Copilot if you would rather recreate the look in a chat. Nothing to install and no account needed. Built with Next.js, open source under MIT.
A browser-first design editor for posters, social graphics, and anything else that lives on a canvas. It handles text, shapes, images, vector boards, and QR codes, with selection and multi-select, grouping, rotation, cropping, blur, shadows, and alignment. Files stay local in IndexedDB by default; export to PNG, JPG, WebP, or JSON and import back. There is an AI-assisted panel and an optional backend for Unsplash and remote media. Mobile editing is blocked on purpose. Open source, AGPL-3.0.
A map front end for BRouter, a routing engine that works off OpenStreetMap data - built mainly for cycling and hiking, where the point is a good route rather than the shortest one. Drop points, drag the line, read the elevation profile, switch routing profiles and base layers, edit waypoints, and export the track. No signup, and public instances are already running. This repo is the web client only; the engine and the routing profiles live in the separate BRouter project. Open source, MIT.
Fifty-odd PDF tools that run entirely in the browser: merge, split, rotate, watermark, sign, OCR, compress, and convert to and from images. Nothing is uploaded anywhere - all processing happens client-side. Deploy it with docker compose or just drop the static build on any host; an air-gapped bundle is available for closed networks. Dual licensed: AGPL-3.0 for free use, or a one-off $79 commercial licence if you ship it inside proprietary software.
A visual editor for cubic-bezier curves: drag the control points and a live preview animates alongside - translate, scale, opacity - so you judge how the easing feels rather than how the graph looks. It comes with a preset library, optional grid snapping, vertical panning for overshoot curves, and light and dark themes. The finished cubic-bezier() value copies to the clipboard in one click. Runs in the browser with nothing to install. React and TypeScript, open source under MIT.
A pastebin for things you would rather not leave on someone else's server: the note is encrypted in the browser with AES-256-GCM, and the key lives in the URL fragment after the hash, which browsers never send upstream. The first reader burns it - everyone after that gets a 410. Unread notes expire in 24 hours, and you can add a password on top. No accounts, safely rendered markdown and syntax highlighting, plus a CLI client on npm. Deploys as a single Cloudflare Worker. Open source, MIT.
A 3D model editor built for low-poly shapes with pixel-art textures - the standard tool for Minecraft models and resource packs, with dedicated formats for both Java and Bedrock editions. It also exports to the usual formats for game engines and 3D printing. The interface is approachable for beginners yet customisable, and JavaScript plugins extend what it can do. Available both in the browser and as an Electron desktop app. Open source under GPL-3.0; whatever you make stays yours.
Runs genuine late-1990s Windows games inside a browser tab: an x86 emulator compiled to WebAssembly plus a reimplemented Windows runtime - Win32, COM, DirectX. DirectDraw and Direct3D 3-9 are translated to WebGPU, DirectSound to WebAudio. No OS image, no plugins, no server-side streaming: executables and saves sit in the browser's OPFS storage and everything runs locally. Tested titles include Heroes III, StarCraft, Diablo II, Max Payne, Morrowind, and Unreal Gold. Open source, Apache 2.0.
A plain-text editor that lives in a browser tab - no server, no markdown, no rich formatting. Text auto-saves to browser storage and survives a reload. It does search and replace with regex, tab indent and dedent, line wrapping at a width you choose, current-line highlighting, case conversion, line/word/character counts, a night mode, file import and export, and a permalink that carries the text in the URL. Feature creep is refused on principle. Open source under the ISC licence.
Shows what an npm package will cost you before you install it: minified and gzipped size, an estimate of download time on a slow connection, a breakdown by dependency, and a chart of how the size drifted across versions. It understands ES modules and packages that ship CSS or SCSS. Most useful at the exact moment you are picking between two libraries and want the price tag. There is an API and a README badge, and no signup. Open source under MIT.
For when a CSV arrives broken - stray whitespace, empty rows, dates and phone numbers in five different shapes. Load it, look at it, fix it, export it again. Virtual scrolling keeps files of millions of rows usable, cells are editable inline with fifty steps of undo, and there's search-and-replace across the sheet plus SQL queries over the data via AlaSQL. Column stats and a health check point at structural problems. Runs entirely in the browser, MIT-licensed, installable as a PWA.
Editors' picks