About JSON to Table

I have spent most of my career in telecoms, staring at machine-generated data that was never meant for human eyes. This site exists because of one bad night with a subscriber export and a browser tab I should not have opened.

The 2am problem

A provisioning job had partially failed. Somewhere in a 40MB export of subscriber records, a few hundred had the wrong plan applied, and I needed to find them before the billing run at 6am.

The export was JSON. One line. No formatting. My editor opened it and then stopped responding for forty seconds. When it recovered, I was looking at a horizontal scrollbar the width of a football pitch and a wall of {"msisdn":"447700900142","imsi":... repeating into the dark.

I did what everyone does. I searched for "JSON viewer online", clicked the first result, and had the file half-selected before I stopped.

That file had real MSISDNs in it. Real IMSIs. Those are personal data under GDPR, and I was about to paste them into a website belonging to someone I could not name, hosted somewhere I had not checked, with a privacy policy I had not read. Nothing bad happened, because I closed the tab. But I had come within one keystroke of a genuinely serious mistake, at 2am, because the tool I needed was easier to find than the tool I could trust.

What actually bothered me

It was not that online tools exist. It was that you cannot tell from the outside which ones send your data anywhere. Two sites look identical. One does everything in your browser; the other posts your file to a server, logs it, and maybe keeps it. Same clean layout, same "free online converter" headline, completely different risk.

And the people most exposed to that are the people least equipped to check — the analyst who was handed an export, the support engineer chasing one ticket, the junior developer three weeks into their first job. They are not being careless. They are being efficient, with no way to see the difference.

So the rule here is simple

Nothing you paste into this site is ever transmitted anywhere. Every tool runs entirely in your browser, using the parsers already built into it — JSON.parse, DOMParser, XMLSerializer. There is no upload step because there is no server to upload to. Turn off your wifi after the page loads and everything still works. That is not a claim you have to take on faith; it is a thing you can verify in about five seconds.

That constraint shapes what this site can be. There is no account system, no history, no cloud sync, no "share a link to your data" that quietly means "we stored your data". Some features are genuinely off the table because of it. That trade is deliberate, and I would make it again.

Why it looks the way it does

Every tool here started as something I wanted at a specific moment. The table view exists because scanning columns is how humans find an anomaly in three hundred records, and reading nested braces is not. The diff tool exists because "it worked in staging" usually means two config files disagree in one place. The validators exist because a parse error with a line number is worth more than an hour of squinting.

Nothing here is trying to be a platform. They are small, sharp tools that do one thing, load fast, and get out of your way.

The guides

I have onboarded a lot of junior engineers, and the same questions come around every time — why won't this file open, what is a namespace really, when should I use XML. The answers are usually simple once someone says them plainly, and weirdly hard to find written that way. So I started writing them down: the explanation I would give sitting next to you, with real examples, including the parts that are genuinely confusing rather than pretending they are not.

If something is wrong, tell me

If a tool mangles your data, a guide is misleading, or something is just broken, I would rather hear it. It is one person maintaining this, so replies are not instant, but every message is read. Get in touch here.

Built and maintained by one engineer who has debugged enough production data at unreasonable hours to care about this properly.