Everything in the catalog

Tests, explains and debugs regular expressions across several flavors such as PCRE2, JavaScript and Python, with code export.

Community library of regular expressions searchable by topic, with a tester.

Tests one regular expression against many engines such as Java, Go, .NET and PCRE.

Hosted test API with users and auth responses for front-end demos and request practice.

Ruby regular expression editor that highlights matches in real time.

Produces sine wave lookup tables for microcontroller DAC or PWM code.

Tests an SMTP server configuration by attempting a connection and test message.

JSON parser that reports errors in Chinese and marks the failing position.

Computes and visualises CSS selector specificity.

Generates, explains, optimizes and validates SQL from plain-English requests.

Formats SQL statements with configurable options.

Browser-based development environment that runs Node-based web projects with WebContainers.

GraphiQL interface wired to the Star Wars API for practising GraphQL queries.

Turns a description into SQL for MySQL, PostgreSQL and other databases.

Runs code in hundreds of languages, mainly used for code golf and quick experiments.

Generates a modern tsconfig.json from a few toggles.

Collection of ready-made regular expressions for emails, URLs, phones and other formats.

Replace github with uithub in a repo URL to get its files as one text blob suited for LLM prompts.

Converts epoch time to readable dates and back and shows the current Unix time.

Checks whether a CNH number's check digits are valid.

Checks whether a CNPJ number's check digits are valid.

Checks whether a CPF number's check digits are valid.

JavaScript 6502 assembler and emulator with debugger and memory view.

Checks CSS against W3C specifications by URL, upload or text.