Everything in the catalog

Online shell for running SymPy symbolic maths in Python.

Markdown editor with live preview, LaTeX math support and GitHub-style rendering in the browser.

Single-page authenticator app that produces one-time passwords, similar to Google Authenticator.

Fill in a 5th Edition D&D character sheet online with automatic modifiers and printing.

Renders Gerber files in the browser and exports the board as SVG or PNG.

Wordle-style game where you guess the next moves of a real chess game with color feedback.

Audits PDF files to check whether redacted text is only covered visually and can still be recovered.

Loads a G-code file and plays back the toolpath layer by layer in 3D.

Small collection of solitaire and patience card games.

Bibliography generator from the Zotero team covering thousands of citation styles, with no account.

Generates FIRST, FOLLOW and PREDICT sets for a grammar, to help when designing a programming language.

Compares one Chinese character across simplified, traditional, seal and oracle bone forms, with Shuowen entries and ancient pronunciations.

Calculator for binary arithmetic and bitwise operations that works on phones and desktops.

Splits a secret message into QR codes so it can be shared and later recovered.

Converts DuckyScript (USB Rubber Ducky) scripts into Python applications.

Converts MIDI songs into Overwatch Workshop code so they can be played in a custom game.

A bookmarklet that saves a ChatGPT conversation as a Markdown file.

Keyboard-driven JSON formatter and editor that works privately in the browser and can be installed as a web app.

Browse the files inside any npm package in the browser, built on unpkg.

Web-based generator for random passwords and diceware-style passphrases.

Collection of web-based utilities for everyday tasks, including converters and data manipulation, which can also be self-hosted.

Converts between Unix epoch timestamps and human-readable dates.

Online converter that turns MySQL dump SQL into SQLite-compatible SQL.

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