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Free developer tools that never upload your data

Format JSON, encode Base64 and URLs, convert JSON to CSV, generate UUIDs and QR codes, convert Unix timestamps, minify HTML CSS and JavaScript, test regular expressions and inspect JWTs. All client-side.

JSON Formatter & Validator

Format, minify and validate JSON with exact line and column errors.

Base64 Encoder & Decoder

Encode and decode Base64 for text and files, with correct UTF-8 handling.

URL Encoder & Decoder

Percent-encode, decode, build query strings and dissect any URL.

JSON to CSV Converter

Convert JSON to CSV and back, flattening nested data with dot notation.

UUID Generator

Generate cryptographically secure UUID v4 or time-ordered v7 in bulk.

QR Code Generator

Create custom QR codes as PNG or SVG, with logo, colours and error correction.

Unix Timestamp Converter

Convert Unix timestamps to readable dates and back, in UTC and your local time.

HTML Minifier

Strip HTML comments and whitespace and see the byte savings instantly.

CSS Minifier

Strip CSS comments and whitespace, and shorten colours and units safely.

JavaScript Minifier

Mangle names and compress JavaScript with terser, entirely in your browser.

Regex Tester

Test regular expressions with match highlighting, group breakdown and flags.

HTML & CSS Snippet Generator

Build clean HTML and CSS boilerplate from a form and copy it straight into your project.

JWT Decoder & Inspector

Inspect JWT headers, claims and expiry locally. The token never leaves your device.

Every tool here runs in your browser. That is not a marketing claim, it is the architecture: JSON is parsed by the browser's own JSON.parse, Base64 by the Web Crypto API, regular expressions by the same engine that runs your page, and minification by the same libraries a production build uses. No form posts anywhere.

It also means the tools behave exactly like client-side JavaScript, which is where most subtle bugs live. The Base64 encoder handles UTF-8 correctly so emoji and accents round-trip. The JSON validator reports line and column and names the actual cause instead of saying SyntaxError. The JWT decoder flags expired tokens, audience mismatches and the none algorithm.

Where an answer depends on the language, the tools say which one applies. Base64 padding, URL encoding of spaces and regular expression flag support all differ between JavaScript, Python and .NET, and knowing which set of rules you are under is usually the whole problem.

Developer Tools questions

Are these developer tools really free with no usage limit?

Yes. There is no account, no quota and no watermark. The processing happens in your browser, so there is no server capacity to rate-limit and no request to queue behind.

Is my code or data sent to a server?

No. JSON, Base64 strings, regular expressions, JWTs and minified source are all processed in your browser tab. That matters for two reasons: nothing leaks, and the tools still work on an unreliable connection once the page has loaded.

Can I use these tools for client-side and server-side code?

Yes. Where the answer depends on the language, the tools say so. Base64 and URL encoding behave slightly differently across JavaScript, Python and .NET, and regular expression support genuinely differs between engines - the regex tester flags flags your browser does not implement.

Why does the JWT decoder not verify signatures?

Verification needs the signing key. An HS256 token requires the shared secret and an RS256 or ES256 token requires the server's public key, and neither belongs in a web page. Decoding shows what a token claims; only the party holding the key can establish that it is genuine. The tool says this on screen too.

Which minifier does the JavaScript tool use?

Terser, the same engine used by webpack and Vite, so the output matches what a normal production build produces. The HTML tool uses html-minifier-terser and the CSS tool uses clean-css.

Do the tools work on mobile?

Most of them, yes, with layouts built mobile-first. The image converter is the exception worth knowing about: very large images can exhaust memory on a phone, so the tool checks the canvas limits first and tells you rather than failing.

Not finding what you need?

Tell us which tool would save you time and we will build it. Requests genuinely drive what gets added next.

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