JSON Linter Online for Free
A JSON linter reads your JSON and tells you the exact line and column where it breaks.
JSON.parse only hands you a raw character offset, which is useless when the payload is one 4,000-character line out of a log. Our JSON Linter turns that offset into a line and column, names the rule that was broken (trailing comma, single quote, duplicate key), and lets you jump straight to the spot instead of counting characters by hand.
Using the JSON Linter, Step by Step
- Bring in the JSON: paste it into the editor, drop a .json file on the workspace, or click Upload JSON in the toolbar.
- Pick the check from the sidebar: JSON Linter for syntax errors, Syntax Fixer for auto-repair, Duplicate Key Finder, Depth Analyzer, JSON Diff, or JSON Path Query.
- Read the report: the right pane lists every issue with a line, a column, and a short note on what to change.
- Fix and re-lint: edit the source in the left pane and the report clears the moment the issue is gone.
What You Can Do with AIFreeForever's JSON Linter
Line-and-Column Error Reporting
Line-and-column error reporting turns the raw character offset from JSON.parse into the row and column you can click in your editor.
Auto Syntax Fixer
The auto syntax fixer strips comments, swaps single quotes for double, drops trailing commas, and quotes bare keys so the document parses on the next try.
Duplicate Key Finder
The duplicate key finder catches the keys JSON.parse silently overwrites, so the field you thought was set does not vanish at runtime.
Depth and Complexity Analyzer
The depth and complexity analyzer reports the deepest nesting level and the object, array, and primitive counts so you know how heavy the payload is before processing it.
Recursive JSON Diff
The recursive JSON diff walks both sides of a left/right payload and prints every added, removed, and changed value with the full dot-notation path.
Dot-Notation Path Query
The dot-notation path query pulls a value out of a deeply nested document with a one-line expression like store.books[0].title.
Why Choose AIFreeForever's JSON Linter
| Check | AIFreeForever | Typical Online Tools |
|---|---|---|
| Error Location | Line and column numbers | Raw character offset only |
| Duplicate Keys | Reported per object scope with line numbers | Silently overwritten by the parser |
| Auto-Fix Coverage | Comments, single quotes, trailing commas, bare keys, undefined | None, or single-quote swap only |
| Structure Report | Depth, node counts, size delta | Pass or fail only |
| Privacy | Linting runs on JSON.parse in your tab | Payload uploaded to a server |
Who Should Use Our JSON Linter
- Backend developers: find the broken comma in a 4,000-line config before a service restart fails.
- API integrators: catch a duplicate key in a vendor payload before the missing field becomes a 2 a.m. page.
- Data engineers: measure depth and node counts before piping a feed into a parser with a recursion limit.
- QA testers: diff two fixture files and see exactly which path changed between runs.
Most precise way to find and fix a broken JSON document
Every report on this page gives you a line, a column, and the exact rule that was broken, so the round-trip from "parser failed" to "parser passes" is one targeted edit instead of a binary search through the file.
Pinpoint Errors
Every issue lands with a line and column, so you click straight to the broken character.
Catches the Silent Bugs
Duplicate keys and undefined values are flagged before JSON.parse quietly drops them.
Stays in Your Tab
Your payload never leaves the browser, so a production secret in the JSON stays put.
