I built a browser-based JSON toolkit because I wanted something simple: paste JSON, work with it, and not have to send the data to a server.
The project is called Instant JSON Formatter.
https://instantjsonformatter.com/
The main idea is privacy + speed. The JSON processing happens directly in the browser rather than sending the JSON to an API.
While building it, I realized that formatting valid JSON is actually the easy part.
The difficult part is everything around it.
I spent a surprising amount of time testing things like:
- Missing commas and brackets
- Deeply nested objects
- Nested arrays
- Mixed objects and arrays
- Large JSON payloads
- Malformed strings
- Unexpected primitive values
- JSON that is almost valid but isn't
- Copying values and JSON paths from nested structures
- Comparing two JSON documents
I also worked on auto-fix behavior.
This was probably the most frustrating part.
It is easy to make an "auto-fix" button that changes something and produces valid JSON. It is much harder to make sure the fix doesn't accidentally change what the user actually meant.
So I've been deliberately throwing broken and weird JSON at the tools and testing how they behave.
The current toolkit includes:
- JSON Formatter
- JSON Validator
- JSON Minifier
- JSON Viewer / Tree Explorer
- JSON Diff
- JSON conversion tools
I'm still improving it, so I'd genuinely like feedback from developers who work with JSON regularly.
What is something that annoys you about existing JSON tools?
And if you have a particularly nasty JSON example that you think would break a formatter, feel free to throw it at me. I'm looking for difficult test cases.
I'd especially appreciate criticism about bugs, edge cases, performance, or UX rather than just "looks good."
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