↳ Developer tools
Developer tools at the speed of paste.
Format JSON, decode JWTs, encode Base64, convert timestamps, and generate UUIDs. Every tool runs in your browser with no install, no API key, and nothing sent to a server.
Developer tools are small utilities that format, convert, encode, decode, or generate the data developers work with every day. This set covers the common ones: a JSON formatter, a Base64 encoder, a JWT decoder, a UUID generator, hash and timestamp tools, and converters between JSON, CSV, YAML, and XML.
They share one promise. Everything runs client side in your browser, so the payloads you paste, the tokens you decode, and the configs you convert never leave your machine. That makes them safe for production secrets and private data, with no npm install and no rate limits.
Reach for the formatters when you need to read or ship minified code, the encoders and converters when data needs to change shape, and the generators when you need a UUID or a hash on demand.
All developer tools
14 toolsWhich developer tool should I use?
- Base64 Encoder / DecoderEncode or decode Base64, including file downloads.
- CSS Formatter / MinifierBeautify CSS to read it or minify it to ship it.
- Hash GeneratorGenerate MD5, SHA, and other checksums from text.
- HTML Entity Encoder / DecoderEscape or unescape HTML entities safely.
- HTML Formatter / MinifierIndent HTML for reading or minify it for shipping.
- JSON ↔ CSV ConverterConvert JSON to CSV, or CSV back to JSON.
- JSON FormatterFormat, validate, and minify JSON, and catch the line a syntax error breaks on.
- JWT DecoderDecode a JWT to inspect its header and payload.
- Number Base ConverterConvert between decimal, binary, hex, and octal.
- Unix Timestamp ConverterConvert Unix timestamps to readable dates in any timezone.
- URL Encoder / DecoderPercent-encode or decode URLs and query strings.
- UUID / GUID GeneratorGenerate random v4 UUIDs on demand.
- XML Formatter & ValidatorValidate, pretty-print, or minify XML.
- YAML ↔ JSON ConverterConvert between YAML configs and JSON objects.
Frequently asked questions
What are developer tools?
Developer tools are utilities that format, convert, encode, decode, or generate the data developers work with, such as JSON, Base64, JWTs, UUIDs, and timestamps. ToolBook runs them all in one browser tab, so you do not have to install a package or hop between sites for each one.
Are these developer tools free to use?
Yes. Every developer tool here is free and runs entirely in your browser, with no npm install, no API key, and no rate limits.
Is it safe to paste sensitive data like tokens and secrets?
Yes. These tools process everything on the client side, inside your browser, so the JSON, JWTs, and payloads you paste never travel to a server. That makes them safe for production secrets and private data.
Which tool formats and validates JSON?
The JSON formatter pretty-prints, validates, and minifies JSON, and points to the line where a syntax error breaks parsing. To reshape the data instead, the JSON to CSV and YAML to JSON converters handle format changes.
How do I decode a JWT?
Paste the token into the JWT decoder. It splits the token and shows the decoded header and payload so you can inspect the claims. Decoding happens in your browser, so the token is never sent anywhere.
Can I use these tools offline?
Mostly yes. Once a tool page has loaded, the work happens in your browser, so most tools keep working without a connection. They need no server round trip to format, convert, or generate.