Validate JSON

JSON.parse fails quietly in one place and loudly in another, usually at the worst possible moment. Validate JSON runs your payload through the browser JSON engine and gives you a straight answer: VALID, with a summary of what you pasted, or INVALID, with the parser message plus the exact line and column where it stopped.

An optional duplicate-key audit catches a subtler class of bug — repeated keys that the parser silently collapses to the last value. Together they make the tool an ideal gate before shipping a config, a payload or a generated file. Everything runs locally, so sensitive data never leaves your machine.

• Full JSON syntax check via the platform parser.
• Precise error reporting: message plus line and column where parsing stopped.
• Optional duplicate-key audit: flags repeated keys within the same object.
• Value summary: reports the top-level type and document size for valid input.
• Plain-text report you can copy, download or print to PDF.
• Live checking: revalidate as you type with Live enabled.
• Fully local — nothing is uploaded.

1. Paste your JSON or open a file.
2. Toggle the duplicate-key audit if you want repeated keys flagged.
3. Run Validate — or leave Live on to recheck as you type.
4. Read the report. A VALID status includes the top-level type; an INVALID status gives the reason, line and column.
5. Copy, download or print the report if you need a record.

Example 1 — Pre-deployment config check. Before shipping a settings file that must parse on every node, run it through the validator to catch a trailing comma or a stray comment.

Example 2 — API payload debugging. A request that is rejected server-side is usually malformed. Paste the body, read the line and column, and fix the producer rather than the consumer.

Example 3 — Generated export sanity check. Confirm a tool-generated export parses cleanly before it is ingested downstream.

Example 4 — Duplicate key hunt. When merged configs silently override settings, enable the duplicate check to find the repeated keys.

• Catch errors early — before a bad payload reaches a runtime parse.
• Actionable diagnostics — line and column turn a vague failure into a one-line fix.
• Duplicate detection — find keys JSON.parse silently collapses.
• Fully local and private — safe for sensitive data.
• Free and unlimited — no sign-up, no limits.