JSON Validator
Paste JSON and find out whether it is valid, where exactly it breaks, and what quietly went wrong even when it parses.
Syntax colouring is off for this document because recolouring something this large on every keystroke would slow typing down. Every tool still works normally.
- Type
- Depth
- Objects
- Arrays
- Keys
- Values
- Largest array
- Longest key
Where it went wrong
Warnings
Runs entirely in your browser. Nothing you paste is uploaded, and you can confirm that in your browser Network tab.
About this tool
Validation here checks your document against RFC 8259 and names the actual mistake rather than reporting an unhelpful unexpected token. Single quotes, unquoted keys, trailing commas, wrong case keywords, NaN and Infinity, leading zeros and bad escapes each get their own message with a line and column. It also reports duplicate keys, which are legal JSON but almost always a bug: the last value silently wins and the earlier one is discarded. Most validators say nothing at all about them.
How to use
- Paste your JSON into the editor, or load the sample.
- Validation runs as soon as you stop typing. You can also press Validate to run it immediately.
- Read the result above the editor. Errors mark the failing line in the gutter, and warnings are listed with their own line numbers.