Free online developer tools

The small tools developers open fifty times a day, on one two-pane layout: paste on the left, the answer on the right, Copy in the corner. Everything runs in your browser, so tokens, secrets and production data never leave your machine.

JSON FormatterFormat, validate and browse JSON, with errors pointed at by line and column and a one-tap fix.Base64 EncodeText, images and files to Base64, with the URL-safe alphabet and data: URLs for CSS.JWT DecoderRead a JWT's header and claims, see when it expires, and check the signature with a secret or public key on your device.Regex TesterTest a JavaScript regular expression live: matches lit in your text, groups in a table, replace, and a plain-words explanation.URL EncodePercent-encode a value, a whole URL or form data, the difference explained; plus a URL parser with editable parameters.Hash GeneratorMD5, SHA-1, SHA-256, SHA-384 and SHA-512 of text or a file at once, HMAC with a key, and a checksum check that turns green.UUID GeneratorRandom v4 and time-ordered v7 UUIDs, one or a thousand, as lines, JSON, SQL or CSV, plus a checker.Unix Timestamp ConverterThe current Unix time ticking, any timestamp to a date in your zone, UTC and another, and a date back to a timestamp.Color ConverterAny colour to HEX, RGB, HSL, HWB, CMYK, Swift and Android, with WCAG contrast, tints and shades and the nearest CSS name.Diff CheckerCompare two texts side by side with the changed words lit, options to ignore case and spaces, and a unified patch to copy.

Every tool on ToolboxHere is free, needs no account and runs on your device. New tools are added as people ask for them; suggest one.

About the developer tools

The developer tools share one two-pane layout: paste on the left, read the answer on the right, with keyboard shortcuts for the two actions you repeat all day. JSON Formatter validates, pretty-prints and minifies, points to the exact line and column of an error, and can repair the common mistakes, comments, trailing commas, single quotes. Base64 and URL encoding handle UTF-8 properly. The JWT decoder shows the header and claims, says whether the token has expired, and can verify the signature with a key you paste. The hash generator computes MD5, SHA-1, SHA-256, SHA-384 and SHA-512 and their HMACs, streaming large files so nothing is loaded whole.

Everything is computed by our own code in the browser; no library is called, and there is no server. That matters for these tools in particular: a JWT, a connection string in a JSON blob or a file you hash can be secret, and the online tools people usually use post them to a server. The regex tester runs patterns in a worker and stops a runaway pattern after two seconds; the colour converter gives every form of a colour and its WCAG contrast; the diff checker shows changes line by line and word by word.

Frequently asked questions

Is it safe to paste a JWT or an API key here?

The page never sends what you paste anywhere; the decoding and verification happen in your browser, and the site’s security policy blocks requests to any other server. Even so, treat production secrets with care and rotate a key you have pasted into any website, including this one.

Why does the hash of my file differ from the one the download page shows?

Usually a different algorithm (MD5 against SHA-256) or a file that changed in transit, for example a text file whose line endings an editor converted. The hash generator shows all four algorithms at once so you can compare.

Does the JSON formatter keep the order of my keys?

Yes. It formats the text you gave it and keeps the keys in their original order; nothing is sorted unless you ask for it.

Can the regex tester use my language’s syntax?

It uses JavaScript regular expressions, which cover most of what Python, Java and Go use. Lookbehind works in current browsers; named groups and Unicode classes are supported. The explain panel reads the pattern back in words.

Which tool do I need?

Checking or formatting JSON: JSON Formatter
Encoding or decoding: Base64 Encode, Base64 Decode, URL Encode, URL Decode
Reading a token: JWT Decoder
A checksum or a hash: Hash Generator, SHA-256 Hash, MD5 Hash
A unique id or a timestamp: UUID Generator, Unix Timestamp Converter
A colour in another form: Color Converter, HEX to RGB
Testing a pattern or comparing two texts: Regex Tester, Diff Checker

Other categories

Document toolsMerge, split and convert PDF files.Image toolsCompress, resize and convert photos.AI toolsOn-device AI for text and photos.CalculatorsCalculator, percentages and grades.Islamic toolsPrayer times, Qibla, Ramadan and Hijri dates.FinanceZakat, loans and money maths.Career & businessResumes, invoices and job applications.Utility toolsQR codes, spin the wheel, coin and dice.Clock & timersTimer, stopwatch, alarm and world clock.Text toolsCount words, change case, clean lists.