JSON error locator — runs entirely in your browser

Your JSON is invalid. Jsonwell tells you the exact character where it breaks.

Every validator says “invalid” and leaves you hunting. Jsonwell parses your JSON and reports the line, the column, what the parser expected there, and the offending character marked in context. On success, it reports the shape: key count, nesting depth, largest array, and duplicate keys.

Open the tool Pricing

What you get

Not a verdict — a coordinate.

A 4,000-line config that fails on a trailing comma is a two-minute problem if you know where, and a twenty-minute one if you don’t. Jsonwell skips the verdict and gives you the location, in the exact format a debugger would.

Line 37, column 14. Parser expected ‘,’ or ‘}’ but found ‘x’.

36 "retries": 3,

37 "name": "John" x

— ↓

38 "active": true

The line above and below are included so the mistake reads in context. The offending character sits under the arrow.

The report

Everything you need to fix it in one move.

Line & column

The precise coordinates of the first parse error — line 1-based, column 1-based, no guessing.

Expected token

What the parser needed at that position: a comma, a closing brace, a string key, a value. Reported in plain terms.

Context, marked

The error line plus the line above and below, rendered in monospace with the offending character highlighted.

Shape report

On valid JSON: top-level key count, maximum nesting depth, the largest array, and every duplicate key — legal JSON that most parsers silently accept and almost always a bug.

Privacy by construction

Your JSON never leaves your browser.

Zero operational surface

Jsonwell is a pure client-side tool. Parsing, error location, and structural analysis all run in JavaScript on your machine. There is no API, no account, no stored history, and no data sent anywhere. No file is uploaded to parse. Full detail is in the privacy policy.

One step

Paste. Get the location. Fix it. Repeat.

Free to use, no account. The tool is a single page: a textarea and a report. Open it and paste your JSON.

Paste your JSON now Pricing