Free online developer tools
These are the small utilities you reach for several times a day, built to run entirely client-side. That is a deliberate choice rather than a technical convenience: pasting an API response, a JWT, or a production log into a tool that ships it to someone else's server is a habit worth avoiding, and here there is nothing to avoid because the data never leaves the page. Everything uses the browser's own built-in APIs — the same JSON parser, regex engine, and crypto source your code runs against.
Format and validate JSON online
Format messy JSON with proper indentation and catch syntax errors with clear messages. Free, no signup, and nothing you paste is transmitted.
Encode and decode Base64 online
Encode text to Base64 or decode it back, with full Unicode and emoji support. Free, no signup, and nothing you paste is sent to any server. Free forever.
Encode and decode URLs online
Percent-encode or decode URLs and query string values instantly. Free, no signup, and nothing you paste is transmitted to any server. No email required.
Test regular expressions online
Test a regular expression against sample text and see every match with its capture groups. Free, no signup, and nothing you paste is stored.
Convert Unix timestamps to dates online
Convert a Unix timestamp to a readable UTC date or turn a date into a timestamp. Free, no signup, and nothing you enter is sent to a server.
Convert colours between HEX, RGB, and HSL
Convert a color between HEX, RGB and HSL with a live swatch preview. Free, no signup, and nothing you enter is transmitted to any server. Free forever.
Generate a strong random password
Generate cryptographically random passwords using the Web Crypto API, not Math.random. Free, no signup, and nothing is stored or transmitted.
Decode a JWT online
Decode a JSON Web Token's header and payload instantly in your browser. Signature is not verified. Free, and nothing you paste is transmitted.
Convert HTML to plain text online
Strip HTML tags and decode entities using the browser's own parser, not fragile regex. Free, no signup, and nothing you paste is transmitted.
Generate UUIDs online
Generate cryptographically random UUID v4 identifiers, one at a time or in bulk. Free, no signup, and nothing is transmitted to any server. Free forever.