Developer Tools15 tools

Free developer tools to format, validate, encode and decode

Developer workflows are full of small conversions: an API response that needs pretty-printing, a config file that will not parse, a token payload that needs decoding. The tools in this category handle those conversions instantly, and unlike most online dev tools, they run entirely in your browser. That is not a small detail. The JSON and Base64 blobs developers work with routinely contain API keys, auth tokens and customer data, and pasting them into a site that uploads to a server is a quiet security risk. Here, nothing leaves your machine.

The JSON formatter pretty-prints, minifies and validates JSON with clear error messages. Paste a single-line API response and get readable, properly indented output. Paste a broken config file and the validator points at the trailing comma or single quote that broke it. It handles large payloads quickly because there is no upload round trip, just the browser's native parser.

The Base64 encoder and decoder converts text to Base64 and back with full UTF-8 support, so emoji and non-Latin characters survive the round trip. Base64 shows up everywhere: Basic Auth headers, data URIs, JWT payloads, Kubernetes secrets, MIME attachments. Being able to decode a blob on sight is a daily debugging skill, and the two tools chain naturally. Decode a JWT segment here, then pretty-print the resulting JSON in the formatter.

Web work has its own set. The regex tester highlights matches live and previews replacements, the JWT decoder reads a token header and payload on your own machine and says plainly that decoding is not verifying, and the UUID generator uses the browser cryptographic randomness rather than something that merely looks random. For data shapes there is XML to JSON in both directions with its conventions written on the page.

The lookup tools reach out to public services and name exactly what travels: DNS lookup resolves records through Google public DNS over HTTPS, and IP address lookup shows your own address plus an honest section on how rough IP geolocation really is. Everything else stays local: hash generator for checksums, URL encoder and decoder for query strings, timestamp converter for epoch values, color converter between HEX, RGB and HSL, and the contrast checker that gives a real WCAG ratio with AA and AAA verdicts.

Adjacent tools round out the workbench. The case converter normalizes identifiers and headings in bulk, the random number generator fills test fixtures with fair random values, and the password generator creates throwaway credentials for test accounts using cryptographic randomness. Everything is free, instant and account-free, with no rate limits and no upload caps. This is the tab you keep open next to your editor, from the first API call of the morning to the last debugging session of the day.