JSON Validator
Validate API and AI-generated JSON with detailed error messages and line numbers
Catch syntax issues before they reach production
A validator tells you exactly where a payload stops being valid JSON. That matters when an AI model emits malformed output, an API returns broken data, a config file breaks a deploy, or a fixture fails in CI and the error message is too vague to trust at a glance.
Use the validator when you need to
Confirm a payload is valid JSON
Run a fast syntax check before you feed the data into an API client, parser, or schema validator.
Pinpoint line and column errors
Find the exact location of missing commas, bad quotes, truncated objects, or other parse failures.
Triage malformed fixtures, config files, and model output
Validate copied request bodies, seed files, local config, and structured AI output before they break a deploy or test run.
How to validate JSON quickly
- 1
Paste the JSON payload into the editor.
- 2
Click Validate to run the syntax check and inspect any reported line and column errors.
- 3
If it fails, repair the payload or apply a suggested fix, then validate again.
Keep going
Repair invalid JSON
Fix common syntax mistakes automatically before validating again.
Understand parser errors
See what common error messages mean and how to resolve them faster.
Learn how to fix invalid JSON
Work through the most common mistakes developers hit in real payloads.
Validate against a schema
Move from syntax validation to contract validation when shape matters too.
Common validator workflows
Paste the response to isolate whether the issue is syntax, truncation, or an unexpected literal.
Validate it first so you know whether the bug is in the JSON or in the request itself.
Use the exact error position to repair the file without diffing every line manually.
Related Tools
JSON Formatter
Beautify JSON from APIs, AI tools, and logs with configurable indentation
JSON Repair
Auto-fix malformed JSON from APIs, AI tools, and copied logs
JSON Schema Validator
Validate JSON, LLM outputs, and tool inputs against a JSON Schema
JSON Viewer
Explore JSON with interactive tree, table, and raw views
Frequently Asked Questions
Paste your JSON into the editor and click Validate. The tool checks your JSON against the official RFC 8259 specification and shows exact line numbers and descriptions for any errors found.
The top five JSON errors developers encounter are: trailing commas after the last item, single quotes instead of double quotes, unquoted property names, missing commas between items, and comments (JSON doesn't support comments).
No. Standard JSON (RFC 8259) does not support comments of any kind — not //, not /* */, not #. If you need comments, consider JSONC or JSON5 formats, or use our JSON Repair tool to strip comments automatically.
Invisible characters are a common culprit. Check for non-breaking spaces, zero-width characters, or BOM markers. Also watch for smart quotes (curly quotes) that text editors sometimes auto-insert.