18 free tools
Developer
Format, validate, decode, debug. Each listed tool has free public access, with processing and account requirements labeled where applicable.
- Free public access
- Account rules labeled
- Processing clearly labeled
- Instant results
Most used developer tools
JSON Formatter
Validate, format, and minify JSON with 2-space, 4-space, or tab indentation, size statistics, copying, and download.
UUID/GUID Generator
Generate 1 to 5,000 random version 4 UUIDs with optional hyphens, uppercase letters, braces, and quotes.
JWT Decoder
Decode JWT header, payload, signature, registered claims, and expiry, with optional client-side HMAC verification for HS256, HS384, and HS512.
Regex Tester
Test JavaScript regular expressions against sample text with live match highlighting, capture groups, match counts, and flag controls.
All developer tools
Base64 Encoder / Decoder
Encode Unicode text as Base64 or decode Base64 back to readable UTF-8 text, with copying, swapping, samples, and text download.
URL Encoder / Decoder
Percent-encode URL components or decode percent-encoded text, with samples, swapping, copying, and text download.
JSON Formatter
Validate, format, and minify JSON with 2-space, 4-space, or tab indentation, size statistics, copying, and download.
JSON to TypeScript
Generate TypeScript interfaces from valid JSON objects and nested API-response samples, with copying and `.ts` download.
SQL Formatter
Format SQL with uppercase keywords and two-space indentation for six selectable database dialects.
Color Contrast Checker
Calculate the contrast ratio between text and background colors and check WCAG AA and AAA thresholds for normal and large text.
URL Query Parser
Parse a URL into its base path, hash fragment, and editable query parameters, then rebuild and copy the result.
Mock Data Generator
Generate up to 1,000 synthetic profile records as JSON or CSV with selectable fields for development and UI testing.
CSV ↔ JSON Data Converter
Convert CSV to JSON or JSON to CSV with validation, delimiter and header controls, nested data, column mapping, preview, and download.
UUID/GUID Generator
Generate 1 to 5,000 random version 4 UUIDs with optional hyphens, uppercase letters, braces, and quotes.
JWT Decoder
Decode JWT header, payload, signature, registered claims, and expiry, with optional client-side HMAC verification for HS256, HS384, and HS512.
Regex Tester
Test JavaScript regular expressions against sample text with live match highlighting, capture groups, match counts, and flag controls.
Hash Generator
Generate MD5, SHA-1, SHA-256, and SHA-512 hexadecimal digests from text as you type, with individual copy controls.
HTML Formatter
Beautify HTML with two-space indentation or minify spacing, with byte statistics, copying, samples, and file download.
CSS Minifier
Remove CSS comments and unnecessary whitespace, show size savings, and copy or download the minified stylesheet.
JS Beautifier
Expand minified or cramped JavaScript into readable two-space-indented code with copying, samples, and `.js` download.
Code Compare
Compare two text or code versions in a Monaco diff editor with split or inline views, syntax modes, file loading, statistics, and fullscreen.
Cron Expression Generator
Build a five-field cron expression, read its plain-English interpretation, inspect field guidance, and copy the result.
Why use these developer tools
Keep payloads private
Format a response or decode a token without pasting it into an unknown website. The JSON Formatter and JWT Decoder run locally, so API responses and tokens stay on your machine.
One tab for the tedious parts
Pretty-print, minify, diff and validate in the browser instead of wiring up a script. The Regex Tester shows matches as you type.
Copy-ready output
Every result is formatted for pasting straight back into your editor — no trailing noise and no sign-up wall.
What you can do with Developer
Pretty-print a minified API response with the JSON Formatter to read its structure at a glance.
Inspect a token's claims and expiry with the JWT Decoder while debugging authentication.
Test a tricky pattern against sample input in the Regex Tester before shipping it.
Seed a database or write tests using the Mock Data Generator and the UUID/GUID Generator.
How to choose the right tool
Cleaning up code?
Use the JSON Formatter for JSON, the SQL Formatter for queries, and the HTML Formatter or CSS Minifier for markup and styles.
Inspecting a value?
The JWT Decoder reads token payloads, the URL Query Parser breaks a link into its individual parameters, and the Base64 Encoder / Decoder turns encoded strings back into readable text.
Generating test data?
The Mock Data Generator builds sample records and the UUID/GUID Generator creates unique identifiers on demand.
About Developer
Streamline your coding workflow with our suite of developer tools designed for speed and privacy. Whether you need to format minified JSON, validate configurations, decode JWT payloads, encode or decode Base64 and URL strings, or test complex regular expressions, this collection provides instant, browser-based solutions. Eliminate the need for bulky software or sending sensitive payloads to external servers. All operations happen client-side, ensuring your proprietary code, API keys, and server logs remain completely confidential while you debug and optimize your applications.
Developer tools run in your browser and don't transmit what you paste. Even so, treat tokens and secrets carefully — decoding a JWT here is local, but a leaked token is a risk anywhere it's shared.
Frequently asked questions
Do these tools send my code anywhere?
Is the JWT Decoder safe for real tokens?
Are there usage limits?
Can I use the output commercially?
Related Reading
From the blog
What is JSON and how to format it correctly
A practical guide to JSON syntax, the mistakes that break it, and how a formatter turns a wall of text into something you can actually debug.
From the blog
Password best practices in 2026
Why length beats complexity, how passphrases work, and a realistic system for managing passwords without losing your mind.