Fix JSON Online
A JSON fixer is a tool that takes a JSON document a parser refuses to load and rewrites the small errors that broke it, so the document loads.
The usual cause is something most editors will not warn you about: a trailing comma a colleague left in a config, single quotes a NoSQL export pasted in, an unquoted key from a JavaScript object literal, a stray comment, or an undefined value the previous service emitted. Our JSON Fixer matches the parser error to the right repair and shows you exactly what it touched, so you can sign off the diff before committing the file.
How to Use the JSON Fixer
- Load the broken document: paste it into the editor, click Upload, or drop a .json, .txt, .geojson, .jsonl, or .ndjson file onto the workspace.
- Run the repair: click Fix JSON, and the tool walks the document, removes trailing commas, swaps single quotes for double, quotes the unquoted keys, strips comments, and replaces undefined, NaN, and Infinity with null.
- Check the diagnostic panel: every change is listed line by line so you can confirm the fixer did not touch anything you wanted to keep.
- Take the clean payload with you: Copy or Download, or switch to the Validator, Beautifier, Diff, Path Finder, or Sort Keys panel in the sidebar.
What Our JSON Fixer Repairs
Trailing Comma Cleanup
Trailing comma cleanup removes the dangling commas after the last item in an array or object that strict parsers reject.
Quote Style Swap
Quote style swap rewrites single-quoted strings as double-quoted JSON strings without touching the content between them.
Unquoted Key Wrap
Unquoted key wrap puts double quotes around bare identifier keys carried over from JavaScript object literals.
Comment Stripper
The comment stripper removes single-line and block comments left over from config files before they reach the parser.
JavaScript Value Coercion
JavaScript value coercion turns undefined, NaN, and Infinity into null because JSON has no native form for them.
Diagnostic Panel
The diagnostic panel lists every fix the repair pass applied, so the diff is reviewable before you commit it.
Why Choose AIFreeForever's JSON Fixer
| Feature | AIFreeForever | Typical Online Tools |
|---|---|---|
| Repair Coverage | Commas, quotes, unquoted keys, comments, BOM, undefined, NaN, Infinity | Commas and quotes only |
| Change Log | Every fix listed in the diagnostic panel | No log of what was changed |
| Bundled Tools | Validator, Beautifier, Diff, Path Finder, Sort Keys on the same page | Fixer only, other tools on separate pages |
| Privacy | Repair pass runs locally in your browser | Payload sent to a server |
| File Support | .json, .txt, .geojson, .jsonl, .ndjson | .json only |
For Backend Developers, Data Engineers, and API Integrators
When a hand-edited config breaks on one trailing comma or a NoSQL export comes in with single quotes, our JSON Fixer repairs the offending characters in one pass. You paste the broken payload and get back a version the parser will load, no matter which rule the original file broke.
Fastest way to unbreak a broken JSON payload
Our JSON Fixer reads the parser error first and runs only the repair that the error points to, so the rest of your document stays byte-for-byte the way you wrote it.
Targeted Repairs
Each fix is matched to a specific parser error, so nothing else in the document gets rewritten.
Reviewable Diff
The diagnostic panel names every change so you can sign off the repair before committing.
Stays in Your Browser
Your payload is parsed and repaired on your device, with no upload step in between.
