Developer Tools
Free Developer Tools
A complete kit of privacy-first developer utilities — format and validate JSON, encode Base64, hash text, decode JWTs, test regular expressions, build cron schedules, design CSS gradients and preview Markdown. Everything runs entirely in your browser, so your code and secrets never touch a server.
Base64 Encode / Decode
Convert text or files to and from Base64 instantly in your browser.
Code Formatter
Beautify, minify and validate JSON, HTML, CSS, SQL, XML and YAML.
Regex Tester & Builder
Test patterns against text and build common regex from presets.
Slug / URL Encoder
Clean broken URLs or turn any title into a safe URL slug.
Hash Generator
Compute SHA-1/256/384/512 digests of any text, instantly on-device.
Color Converter
Convert HEX, RGB and HSL and check WCAG contrast in real time.
Unix Timestamp Converter
Convert between Unix time, ISO 8601 and human dates both ways.
JWT Decoder
Decode JWT header and payload locally — no secret, no upload.
Crontab Schedule Creator
Build and decode cron expressions with plain-English explanations and next run times.
Number Base Converter
Convert between binary, octal, decimal and hex — plus a bitwise calculator.
Text Encryptor
Password-protect text with AES-256 encryption, right in your browser.
Webmaster File Generator
Generate robots.txt, sitemap.xml and .htaccess files in seconds.
JSON to TypeScript
Paste a JSON payload, get TypeScript interfaces — nested, named and merged.
CSS Gradient Generator
Design linear, radial and conic CSS gradients with a live preview.
Markdown Previewer
Write Markdown and see the rendered HTML side by side, instantly.
Document Privacy Inspector
See what a PDF or Office file says about you, then strip it.
CSS Theme Generator
Turn one brand colour into full light and dark themes with OKLCH ramps.
Flexbox Playground
Set every flex property with a control, watch the boxes move, copy the CSS or Tailwind.
CSS Grid Playground
Build a grid with sliders and selects, span cells by clicking them, copy the CSS or Tailwind.
SVG Optimizer
Shrink an SVG with SVGO — sizes before and after, gzipped too — and get it back as a React component.
Sensitive Data Scanner
Find emails, card numbers, keys and tokens in text or logs and redact them — or swap them for reversible stand-ins before an AI sees them.
OAuth Flow Simulator
Step through OAuth and OpenID Connect flows with tokens minted in your browser.
Encryption Algorithm Simulator
Watch AES, SHA-256, RSA and Diffie-Hellman work, one step at a time.
HTML & CSS Playground
Write HTML, CSS and JavaScript and see it render, with a console for what it logs.
Which developer tool?
One line each: the situation the tool is the answer to.
| Tool | Best when |
|---|---|
| Code Formatter | A payload or config is unreadable, invalid, or needs converting between JSON, YAML and CSV. |
| JSON to TypeScript | You have a JSON sample and need the TypeScript types for it. |
| Regex Tester & Builder | A pattern does not match what you expect, or you need to see every match in a log file. |
| Crontab Schedule Creator | You need to know when a schedule fires, or write one without guessing the fields. |
| JWT Decoder | A token is being rejected and you want to see its claims and expiry. |
| OAuth Flow Simulator | The sign-in itself is the problem: which request carries which parameter, and why. |
| Encryption Algorithm Simulator | You want to see inside a cipher or a hash rather than call one. |
| HTML & CSS Playground | A snippet of markup, styling or script you want to see render right now. |
| Base64 Encode / Decode | Something is base64 and you need the text, or the other way round. |
| Hash Generator | A download should match a published checksum, or you need a digest of some text. |
| Unix Timestamp Converter | A Unix timestamp needs to become a date, or a date a timestamp. |
| Color Converter | A colour is in the wrong notation, or two colours need a contrast check. |
| CSS Gradient Generator | You want CSS for a gradient you can see while you tune it. |
| Markdown Previewer | A README or post should be checked before it is pushed. |
| Slug / URL Encoder | A title needs to become a URL, or a query string needs encoding. |
| Number Base Converter | Hex, binary, octal and decimal, plus bitwise operations. |
| Text Encryptor | A secret has to travel over a channel you do not trust. |
| Document Privacy Inspector | A document is about to leave the building and you want to know what it carries. |
| Webmaster File Generator | A new site needs robots.txt, a sitemap and the other root files. |
| CSS Theme Generator | One brand colour has to become a whole light and dark theme, as CSS variables or a Tailwind config. |
| Flexbox Playground | A row or column will not align the way you expect and you want to see each property move the boxes. |
| CSS Grid Playground | A layout needs columns, gaps and cells that span, with the CSS written for you. |
| SVG Optimizer | An exported SVG is bloated, or you need it as a React component with the attributes already renamed. |
| Sensitive Data Scanner | A log, export or config is about to be shared and you need the emails, numbers and keys found and redacted first. |
Most of these accept text from each other through Send to, so formatting, hashing and encoding chain without copy-paste.
About these developer tools
Most day-to-day development involves a small set of recurring text operations, and the errors cluster where they look interchangeable. Encoding, encryption and hashing are the classic case: all three turn readable input into something unreadable, and only one of them protects anything. The tools here keep those distinctions explicit — the Base64 page tells you it is not encryption, the hash generator explains why a digest cannot be reversed, and the JWT decoder is clear that decoding proves nothing about a signature.
The pages are built for the debugging workflow rather than one-off conversions. Payloads chain from one tool into the next — decode Base64, then hash the result, or format JSON pulled out of a token — and the regex and cron tools show their work as you type, because those two syntaxes are where a silent misreading costs the most. Everything here also works offline once loaded, which matters the day you are debugging on a train.