Toolkit
20 free tools

Free developer tools

Format and validate JSON, test regular expressions, decode JWTs and user agents, generate UUIDs, hashes, passwords and placeholder text, encode Base64 and URLs, calculate subnets and chmod values, and test a keyboard, mouse or screen. All of it runs in your browser, so tokens and keys are never sent to us.

All 20 run in your browser

Every tool in this category

Sorted A to Z. All free, with no account and no sign-up.

Barcode Generator

Generate validated Code 128, EAN, UPC, ITF-14, Code 39, and QR barcodes with SVG, PNG, and printable label-sheet output.

Base64 Encoder & Decoder

Encode Unicode text and files to Base64 or decode Base64 into text and downloadable files, with data URL and URL-safe support.

Chmod Calculator

Build a Unix file mode from checkboxes, read any octal or symbolic mode back, and copy the exact chmod command with setuid, setgid, and sticky bits explained.

Color Picker & Converter

Pick and convert HEX, RGB, HSL, and CMYK colors, generate harmonious palettes and shades, check WCAG contrast, and export CSS variables.

CPS Test

Run a click speed test from 1 to 60 seconds and get your clicks per second, click intervals, consistency, and fastest burst, with best scores kept on this device.

Dead Pixel Test

Fill your screen with solid red, green, blue, white, and black to find dead, stuck, and hot pixels, with fullscreen cycling, keyboard controls, and a uniformity check.

Hash Generator

Hash text or files with MD5, SHA-1, SHA-256, SHA-384, and SHA-512, sign messages with HMAC, and verify a published checksum locally.

IPv4 Subnet Calculator

Turn any IPv4 address and CIDR prefix into its network, broadcast, usable host range, mask, wildcard, and a full list of equal-size subnets.

JSON Formatter & Validator

Format, minify and validate JSON with precise diagnostics, recursive key sorting, tree search, and document statistics.

JWT Decoder

Decode a JSON Web Token into its header, payload, and signature, with readable claim dates, expiry status, and algorithm warnings, without sending it anywhere.

Keyboard Tester

Press every key and watch it light up on a full keyboard layout, with key codes, a list of keys not yet tested, chatter detection, and a rollover count.

Lorem Ipsum Generator

Generate placeholder paragraphs, sentences, words, or list items, in plain text, HTML, or Markdown, and fill an exact word or character budget.

Password Generator

Create cryptographically secure random passwords and memorable passphrases without saving or uploading them.

PX to REM Converter

Convert pixels to rem and rem to pixels at any root font size, with a reference table, batch conversion of CSS values, and em for nested elements.

Refresh Rate Test

Measure the refresh rate your browser actually delivers in hertz, with a frame-time graph, dropped frames, a smooth-motion check, and what can cap it.

Regex Tester & Debugger

Test a regular expression against your own text with live match highlighting, capture groups, named groups, replacement preview, and a full token cheatsheet.

Unix Timestamp Converter

Convert epoch seconds or milliseconds to ISO, UTC, local, relative, and time-zone dates, or convert dates and timestamp batches back.

URL Encoder & Decoder

Percent-encode or decode a URL, a query string, or a single parameter, and split any link into its scheme, host, path, query, and fragment.

User Agent Parser

Break a user agent string into browser, engine, operating system, and device, read your own, and see which parts are real and which are legacy padding.

UUID Generator

Generate UUID and GUID values in bulk (random v4, time-ordered v7, classic v1, reordered v6, or deterministic v5) and decode any existing UUID.

Good to know

How these tools work

Safe for secrets

JWTs, passwords and hashes are processed in the tab. You can confirm in your browser's network panel that nothing is sent.

Precise by design

Number base conversion uses exact arithmetic, the regex tester uses your browser's own engine, and the hash generator checks a file against every algorithm at once.

Hardware checks included

A keyboard tester, click speed test, dead pixel test and refresh rate test help when a new keyboard, mouse or monitor arrives.

Questions

Frequently asked questions

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

The tools run entirely in your browser and make no network request with what you paste. Even so, treat production secrets with care and rotate any key you have shared.

Which regex flavour does the tester use?+

JavaScript, through your browser's own RegExp engine. Results match Node.js and browsers but can differ from PCRE, Python or Go.

Are generated passwords and UUIDs random enough?+

Yes. They come from the Web Crypto API's cryptographically secure random generator, the same source browsers use for encryption keys.

Keep exploring

Other categories

PDF

Everything runs in your browser, so a signed contract never leaves your computer. Most of these take files up to 75 MB and 500 pages.

Business

Invoices, receipts and quotes print to an A4 PDF straight from the page. The CV maker and Kanban board save as you go, in this browser rather than an account.

Documents

Draw a signature with a mouse, trackpad or finger, or type one, then download it as a transparent PNG, an SVG or a JPG.

Writing and text

Counters for words, characters, syllables and reading time, a text diff, a notepad that saves locally, and a typing test that compares you with the last hour of results.

Images

Nine of these send the image to our server, where it is converted in memory and not kept. The other eight, including HEIC to JPG and the cropper, never upload anything.

Finance

Loans, mortgages, take-home pay, sales tax, tips, a monthly budget and a splitter for shared costs. The budget and the group ledgers are saved in this browser.

Calculators

The biggest section: dates, ages, grades, units, sleep cycles, dice and timers, plus a scientific calculator that handles complex numbers and solves equations.

Music

A metronome with swing and accents, a pitch pipe, tap tempo, the circle of fifths, and a transposer that reads ChordPro chord sheets.

Audio and video

Check a microphone, speakers or webcam before a call, watch sound on a spectrum analyzer, or record from your webcam. Recordings stay in the tab until you save them.

Crypto

Profit and loss, DCA, staking, gas fees and liquidation prices. Nothing connects to a wallet or a price feed; you type the numbers in.

More focused tools, ready when you are.

Explore the growing collection for calculations, documents, writing, and everyday work.

Browse all tools