Free Developer Tools
A private developer toolbox: JSON formatter, Base64 encoder, JWT decoder, hash generator, regex tester, diff checker and more. Runs offline in your browser.
10 free developer tools
- JSON Formatter — Beautify, validate & minify JSON
- Base64 Encoder & Decoder — Text and files to Base64, both ways
- URL Encoder & Decoder — Percent-encode and inspect URLs
- JWT Decoder — Decode and verify JSON Web Tokens
- Hash Generator — MD5, SHA, CRC32 & HMAC checksums
- Regex Tester — Test regular expressions live
- Diff Checker — Compare two texts line by line
- Unix Timestamp Converter — Unix epoch to date, and back
- Color Converter — HEX, RGB, HSL, HSV, CMYK & OKLCH
- Cron Expression Parser — Explain cron and preview next runs
About these tools
Every developer keeps a scratch tab open for the same handful of jobs: pretty-printing a JSON payload, decoding a JWT to see why auth is failing, Base64-ing a key, hashing a string, checking a regex, diffing two blobs of text. Most of the sites that serve those needs are ad-choked, slow, and — worse — they POST your input to a backend. Pasting a production token into a random web form is a real security incident, and it happens every day.
These tools are deliberately boring in the right ways: no network requests, no telemetry, no cookie banner. Hashing uses the browser’s native SubtleCrypto, JSON parsing uses the engine’s own parser so error messages match what your runtime would say, and every output can be copied or downloaded in one click. Open one tool and the rest are a keystroke away.
They also work offline. Once the page has loaded, you can pull the network cable and everything still functions — handy on a plane, on a locked-down corporate network, or when you simply do not want a third party to see the payload you are debugging.
Frequently asked questions
Are these developer tools safe for production data?
They are as safe as your own machine. Nothing is transmitted: every tool parses, transforms and renders locally in JavaScript. You can verify it by opening DevTools and watching the (empty) network tab while you work.
Do they work offline?
Yes. After the page loads, no further network access is needed. The tools keep working with the connection off.
Is there a rate limit or a paywall?
No. There is no account, no quota and no premium tier — process as much as you like.
Which hash algorithms are supported?
SHA-1, SHA-256, SHA-384 and SHA-512 via the Web Crypto API, plus MD5 and CRC32 implemented in JavaScript for legacy checksums.
Can I use these tools on a phone or tablet?
Yes — every layout is responsive, and code panes scroll independently so nothing overflows the page.
Other tool categories
- PDF tools — Merge, split, compress, convert and organise PDFs without uploading a thing.
- Text & Writing tools — Count, clean, convert and compose text with instant, precise feedback.
- Calculators tools — Money, dates, units and health — answers with the working shown.
- Generators tools — Passwords, QR codes, IDs and palettes — generated locally, never logged.
- Brain & Cognition tools — Measure reaction time, memory, attention and reasoning against real norms.
- Time & Focus tools — Pomodoro, stopwatch, countdowns and time zones — accurate to the millisecond.