I Built a JSON Formatter Because Every Existing One Has Ads

Let me paint you a picture. It's 11pm, I'm debugging an API response, and I just need to format a blob of JSON so I can actually read it. I open the first Google result and get hit with a cookie banner, two pop-ups, and an ad for VPNs covering half the screen.

This happens every single time.

So I built my own JSON formatter. Not because the world needed another one, but because I was tired of fighting through ad-infested tools just to add some whitespace to a JSON string.

What it actually does

JSONPrettify does four things:

1. Formats JSON with proper indentation so you can read it
2. Validates JSON and tells you exactly where the syntax error is
3. Minifies JSON when you need to strip whitespace back out
4. Tree view that lets you expand and collapse nested objects

That's it. No account creation, no premium tier, no "sign up to unlock minification." You paste your JSON, you get your result.

Why browser-only matters

Everything runs in your browser. Your JSON never leaves your machine. I want to stress this because a lot of the popular formatters actually send your data to a server. If you're working with API keys, user data, or anything remotely sensitive, that should bother you.

I've pasted production database exports into JSON formatters before without thinking twice. That was dumb. With JSONPrettify, it doesn't matter because nothing gets transmitted anywhere.

The boring technical stuff

It's a Next.js app. The formatting and validation happen client-side with standard JavaScript. The tree view is a recursive component that lazily renders nodes so it doesn't choke on large payloads. I tested it with a 5MB JSON file and it handled it fine. Your browser might not love it, but the tool won't crash.

The error reporting was the part I spent the most time on. Most formatters just say "invalid JSON" and leave you hunting. I parse the error message to extract the line and character position, then highlight the exact spot where things went wrong. It's not revolutionary but it saves a few minutes of squinting at brackets.

Who this is for

Honestly, anyone who works with JSON and is tired of the existing options. Front-end devs debugging API responses. Back-end devs checking config files. Students learning about data formats for the first time. It's a simple tool for a simple job.

I'm not trying to build a business around this. There's no analytics tracking you, no newsletter pop-up, no plans to add a paid tier. It's just a tool that does one thing well.

If you want to try it: jsonprettify-ruby.vercel.app

If you have feedback or find a bug, I'd genuinely like to hear about it. I built this for myself first, but if other people find it useful, that's a win.