Free online developer tools

Tests JSONPath, JSPath or Lodash-style queries against JSON or XML.

Python editor and interpreter that runs scripts in the browser.

Assembles x86 and x64 instructions into machine code bytes.

Compile, run and step-debug C, C++ and other languages with GDB in the browser.

Online editor and runner for PHP, Java, Ruby, Python, Swift and other languages.

Shows the real install and bundled size of an npm package.

Runs Python code online with input support and instant output.

Decodes raw protobuf bytes without a schema and shows the field tree.

Live editor for testing Python regular expressions against sample text.

Generates React Native shadow styles for iOS and Android elevation.

Proposes starter regular expressions from example strings you type, to refine afterwards.

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.