Free developer tools online
Six utilities for the small jobs that interrupt real work — formatting, encoding, testing and hashing.
Every developer tool here runs locally. Your code, tokens and files are never transmitted.
JSON Formatter & Validator
Beautify, minify and validate JSON with the error line called out.
Tree viewCode Minifier & Beautifier
Minify or expand HTML, CSS and JavaScript and see the bytes saved.
Both waysBase64 Encoder & Decoder
Encode and decode Base64 text, or turn an image into a data URI.
Text + imageURL Encoder & Decoder
Percent-encode and decode URLs and query string values.
2 modesRegex Tester
Test a regular expression live with highlighted matches and groups.
Live matchHash Generator
Generate SHA-1, SHA-256, SHA-384 and SHA-512 from text or a file.
Web CryptoThese are the tools you reach for a dozen times a week and never think about until one of them is not available. Format some JSON to see what an API returned. Decode a token to find out why an authorisation is failing. Test a pattern before it goes into production. Hash a download to check it arrived intact.
They are small jobs, but the usual online versions of them share an uncomfortable property: you paste production data into a stranger's server. API responses contain customer records. Config files contain endpoints and keys. JWTs contain user identifiers. None of that should be leaving your machine to save you thirty seconds.
The six tools
The JSON formatter and validator beautifies, minifies and validates, and when parsing fails it tells you the line and column rather than just refusing. It also has a collapsible tree view for exploring large responses.
The code minifier and beautifier handles HTML, CSS and JavaScript in both directions, protecting strings and regular expressions so nothing inside them is altered, and reports the bytes saved.
The Base64 encoder and decoder handles UTF-8 correctly, supports the URL-safe alphabet used by JSON Web Tokens, and converts images to data URIs.
The URL encoder and decoder offers both component and full-URL modes with the difference explained, and breaks a query string into a readable table.
The regex tester highlights matches live, lists every capture group in a table, and ships with presets for the patterns people write most often.
The hash generator produces SHA-1, SHA-256, SHA-384 and SHA-512 from text or a file using the Web Crypto API, with a comparison box for verifying a published checksum.
Why local processing matters here specifically
For most categories of tool, running in the browser is a nice privacy bonus. For developer tools it is closer to a requirement. The data you put into a JSON formatter is, by definition, data your system produced — and it routinely contains things that should not appear in a third party's access logs.
The hash generator makes the point most clearly. Hashing a file to verify it has not been tampered with, by uploading it to a server you do not control, defeats the purpose of the exercise. Here the Web Crypto API computes the digest on your own machine, so the verification actually means something.
What these tools are not
The minifier is a whitespace and comment stripper, not a compiler. It will not rename variables, remove dead code or tree-shake. For a production build, use a real toolchain — this is for the snippet you are pasting into a customiser box that has no build step behind it.
The regex tester uses the JavaScript engine, so patterns behave exactly as they will in a browser or in Node. PHP, Python and Go differ on lookbehind, named groups and Unicode escapes, so test in your target engine when those come up.
For image-related work such as data URIs and favicons, the image tools cover more ground, and the design tools handle CSS generation.
Frequently asked questions
No. All six tools run entirely in your browser using built-in APIs. Nothing is transmitted or logged, which is the main reason to use these rather than a hosted alternative when the content is production data.
Files of several hundred megabytes work on a normal machine. The file is read into a buffer before hashing, so multi-gigabyte files are better handled by a command line tool such as sha256sum or certutil.
It uses the JavaScript engine. Core syntax is shared across languages, but lookbehind support, named group syntax and Unicode property escapes vary. Verify in your target engine before relying on a pattern.