Don's Tools · Developers

Developer tools

A free set of developer tools that run in your browser. JSON, Base64, regex, hashing, JWT, diff, cron and more.

Developer Tools is a free collection of utilities on Don's Tools that run in your browser with nothing uploaded. It includes a JSON formatter and validator, Base64 encode and decode, URL encode and decode, an HTML, CSS and JavaScript minifier and beautifier, a regex tester with live highlighting, a UUID generator, a hash generator for MD5 and SHA, a JWT decoder, a diff checker and a cron expression builder with next run times.
JSON Formatter & Validator›Base64 Encode & Decode›URL Encode & Decode›HTML, CSS & JS Minify & Beautify›Regex Tester›UUID Generator›Hash (MD5, SHA)›JWT Decoder›Diff Checker›Cron Builder›Colour Converter›Token Counter & Cost Estimator›Embedding & Vector Calculator›cURL to Code›Prompt Cleaner›JSON to TypeScript, Pydantic & Zod›JSONL Viewer & Validator›RAG Text Chunker›Function Calling Schema Builder›Chat Transcript Format Converter›

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Frequently asked questions

Are these developer tools free and private?

Yes. Every tool is free with no sign-up and runs in your browser. Your code, text and tokens stay on your device and are never uploaded; the tools work offline once loaded.

Do I need to install anything?

No. They work in any modern browser with no download, plugin or account, on desktop or mobile.

Which tools are included?

A JSON formatter and validator, Base64 encode and decode, URL encode and decode, an HTML, CSS and JavaScript minifier and beautifier, a regex tester, a UUID generator, a hash generator for MD5 and SHA, a JWT decoder, a diff checker and a cron builder.

Is it safe to paste private code or tokens?

Yes, because nothing leaves your browser. As always, take normal care on shared or public computers.

Do any tools load external libraries?

A few load a small, well-known library on first use, such as the formatter for minifying and the MD5 routine for hashing. Everything still runs in your browser and is cached afterwards.