5 Free Developer Tools That Run Entirely in Your Browser

Mikey Bailey — Fri, 26 Jun 2026 17:58:10 +0000

If you have ever used an online tool that asked you to create an account, verified your email, and then tried to upsell you on a paid plan before letting you format some JSON — you know the pain.

I built DevToolKit as a free, no-signup alternative. Every tool runs 100% client-side in your browser. No data leaves your machine. No cookies. No tracking.

Here are 5 tools from DevToolKit that I use almost daily:

1. Regex Tester

Write a regex pattern, type test strings, and see matches highlighted in real time. Supports flags, capture groups, and a cheat sheet for common patterns.

Try the Regex Tester →

2. JSON Formatter

Paste minified JSON and get a clean, indented view. Detects syntax errors instantly. Also validates structure — unmatched brackets, trailing commas, and more.

Try the JSON Formatter →

3. JWT Decoder

Paste any JWT token and instantly see the header, payload, and signature details. No server calls — decode happens in your browser using base64 parsing.

Try the JWT Decoder →

4. Hash Calculator

Compute MD5, SHA-1, SHA-256, and SHA-512 hashes from any text input. Uses the Web Crypto API — no server round-trips.

Try the Hash Calculator →

5. Base64 Encoder/Decoder

Encode text to Base64 or decode Base64 back to text. Handles UTF-8 properly. Useful for debugging API responses, email attachments, and data URLs.

Try the Base64 Tool →

More Tools

DevToolKit has 15+ free tools including a UUID generator, URL encoder, color converter, HTML entity encoder, timestamp converter, cron parser, diff checker, and more. All at:

nordicnode.github.io/devtoolkit

No signup. No tracking. Just tools.