Developer Tools
Free developer tools that run in your browser
Format JSON, decode a JWT, test a regex, generate a hash. Nothing you paste into these tools is logged, stored or sent anywhere.
35 tools in this collection · See every tool
Developer tools have an awkward habit of swallowing your input. A JWT decoder is a perfect place for a bearer token. A regex tester is a perfect place for an API key or a line of production code. Passing those to a web service means trusting that service with credentials you would not paste into a public pastebin.
Every tool here runs locally in the page, so what you type stays in the tab. The JWT decoder, the JSON formatter, the hash generator and the encoders are all pure client-side code. Paste, get the result, clear the box.
This is the one category where 'files never leave your browser' is less about files and more about text you would rather not paste anywhere. Same guarantee, different kind of data.
All developer tools
Password Toolkit
Generate strong passwords and check their strength.
Hash Generator
Hash text with SHA-1, SHA-256, SHA-384, or SHA-512.
QR Code Generator
Create QR codes from any text or URL and download them.
Base64 Encode/Decode
Convert between text/files and Base64 encoding.
JSON Formatter
Format, validate, and visualize JSON with tree view.
UUID Generator
Generate UUIDs (v1, v4, v7) with customizable formatting.
Unit Converter
Convert between units of length, weight, temperature, data, time, area, volume, and speed.
Text & Code Diff Checker
Compare two blocks of text or code and highlight differences.
CSV ↔ JSON Converter
Convert CSV spreadsheets into JSON arrays (and vice versa) instantly.
URL Encoder / Decoder
Cleanly encode and decode URL query parameters safely.
CSS Formatter / Minifier
Instantly pretty-print messy CSS or minify it for production.
ZIP Viewer / Extractor
View contents of ZIP archives and selectively extract files locally.
Regex Tester
Test regular expressions with live match highlighting, capture groups, and substitution preview.
JWT Decoder
Decode JWT tokens and inspect header, payload, and signature claims.
Word & Character Counter
Count words, characters, sentences, paragraphs, and estimate reading/speaking time.
Text Case Converter
Convert text between different case formats instantly.
Lorem Ipsum Generator
Generate realistic placeholder text for your designs and mockups.
Markdown Preview
Write Markdown and see a live-rendered HTML preview.
XML Formatter & Validator
Format, prettify, and validate XML documents locally.
CSS Minifier & Beautifier
Minify CSS for production or beautify it for readability.
Cron Expression Generator
Build cron expressions visually or describe existing ones in human-readable form.
JSON ↔ CSV Converter
Convert between JSON and CSV formats with ease.
IP Address Lookup
Look up IP address details including location, ISP, timezone, and coordinates.
DNS Record Lookup
Query DNS records for any domain using Cloudflare DNS-over-HTTPS.
HTTP Headers Checker
Inspect HTTP response headers, security headers, and connection timing for any URL.
Port Scanner
Check if common or custom ports are open on a host.
Screen Capture Tool
Capture screenshots of your screen directly in the browser.
Audio Recorder
Record audio from your microphone with live waveform visualization.
Fake Data Generator
Generate realistic fake data for testing — names, emails, addresses, and more.
HTML Minifier
Remove comments, collapse whitespace, and minify HTML for production.
JavaScript Minifier
Remove comments, collapse whitespace, and minify JavaScript.
CSV ↔ Excel Converter
Convert between CSV and Excel (.xlsx) formats with a toggle.
JSON ↔ YAML Converter
Convert between JSON and YAML formats with ease.
CSS Gradient Generator
Create beautiful CSS gradients with live preview.
CSS Box Shadow Generator
Create custom box shadows with live preview and copy-ready CSS.
Developer Tools FAQ
Is what I paste into these tools logged or stored?
No. The processing runs in your browser, so the text never leaves the tab. There is no server copy to log, retain or leak. Clear the box when you are done and it is gone.
Does the JWT decoder send my token anywhere to verify it?
No. It reads and displays the header and payload, and tells you whether the structure is valid. It cannot tell you whether a token is authentic, because that needs the server's signing secret — which is exactly why the secret should not be pasted into a website.
Which hash algorithms are supported?
MD5, SHA-1, SHA-256, SHA-384 and SHA-512. MD5 and SHA-1 are here for compatibility with existing systems; for anything new, use SHA-256 or above.
Are the generated passwords and keys cryptographically secure?
Yes. Random values come from the Web Crypto API's cryptographic random source, not from Math.random. That is the same primitive behind secure cookies and key generation, not a statistical approximation of randomness.
Can I use these tools on a locked-down work network?
Usually. Everything except the lookup tools — IP lookup, DNS lookup, HTTP headers and the port scanner — works with no network access once the page has loaded.