Everything in the catalog

Runs Dart and Flutter snippets in the browser with a console and a live preview pane.

Shows how OpenAI-style tokenizers split text or chat messages into tokens and counts them.

Checks whether an npm package's TypeScript types resolve correctly across module systems.

Compiles and runs Rust code in the browser and shows output, assembly or MIR.

API and page that return random placeholder user profiles with names, photos and addresses.

Upload a wireframe or design screenshot and get a React and Tailwind app generated from it.

Shows the TypeScript compiler's syntax tree and type info for code you paste.

Lints an npm package's package.json and exports so it works across bundlers and runtimes.

Compiles and runs C++ and other languages with many compiler versions and shareable permalinks.

Bundles, minifies and compresses npm packages in the browser to show gzip and brotli size.

Lookup table showing which HTML and CSS features work in common email clients.

Runs Go programs in a sandbox and shares them via link.

Visualises tokens for OpenAI models and estimates prompt cost against context limits.

Runs jq filters on JSON in the browser and produces shareable links to the snippet.

Draws the dependency tree of npm packages as an interactive graph with size and maintainer data.

Interactive 40-pin GPIO reference with add-on boards and pin functions for the Raspberry Pi.

Interactive pin map of the Raspberry Pi Pico showing each pin's functions.

Parses DER, BER and PEM data such as certificates and keys into a readable ASN.1 tree.

Converts code between C# and VB.NET in both directions.

Flashes firmware to ESP chips from the browser over Web Serial.

Offline-capable viewer of tldr-pages command cheat sheets that runs in the browser.

Gives a public channel URL that forwards webhook payloads to your local machine.

Live preview for Discord embed and webhook JSON so you can see how a message will render.

Writes JavaScript for Espruino boards and uploads it over Web Bluetooth or Web Serial.