I Built 10 Free Developer Tools That Run Entirely in Your Browser

#webdev #resources #productivity #javascript

As developers, we constantly reach for small utilities — formatting a JSON blob from an API response, decoding a Base64 string, generating UUIDs for a database seed, or testing a regex pattern before committing it.

Most online tools work fine, but they come with trade-offs: walls of ads, slow load times, or the uncomfortable reality that you're pasting potentially sensitive data into someone else's server.

So I built DevTools Hub — a collection of 10 developer utilities that run entirely in your browser. No backend. No data leaves your machine. No accounts or cookies.

The Tools

Here's what's included:

JSON Formatter & Validator — Beautify, validate, or minify JSON with instant error detection.

Base64 Encode/Decode — Convert text to Base64 and back, handling UTF-8 properly.

UUID Generator — Generate random v4 UUIDs in bulk (up to 1000 at a time).

Hash Generator — SHA-1, SHA-256, and SHA-512 hashes using the Web Crypto API.

URL Encode/Decode — Percent-encode special characters or decode encoded URLs.

Word & Character Counter — Words, characters, sentences, paragraphs, and estimated reading time.

Regex Tester — Test patterns with real-time matching, flags, and capture group display.

JWT Decoder — Decode JSON Web Tokens to inspect header, payload, and expiration status.

Text Diff Checker — Line-by-line comparison with color-coded additions and deletions.

Color Converter — Convert between HEX, RGB, and HSL with a live preview.

Why Client-Side Only?

Everything uses vanilla JavaScript and browser APIs like crypto.subtle for hashing and crypto.randomUUID() for UUID generation. The entire site is a collection of static HTML files with a shared CSS stylesheet — no framework, no build step, no server.

This means:

Privacy: Your data literally cannot be leaked because it never leaves your browser tab
Speed: No network requests, no loading spinners — tools respond instantly
Reliability: Works offline once loaded, no server downtime