JSON Validator & Checker
Paste any JSON code and instantly know whether it is valid. The validator parses your input and, if something is wrong, reports a clear message with the offending position — no more hunting for a missing comma by eye. Valid documents are summarized by type and size, and pretty-printed so you can review your structure at a glance. Everything runs locally in your browser: JSON never leaves your machine.
What is JSON Validator & Checker?
Validate JSON, find the exact error, and see a formatted preview. Paste any JSON code and instantly know whether it is valid. The validator parses your input and, if something is wrong, reports a clear message with the offending position — no more hunting for a missing comma by eye. Valid documents are summarized by type and size, and pretty-printed so you can review your structure at a glance. Everything runs locally in your browser: JSON never leaves your machine. The tool runs 100% in your browser — nothing is uploaded to a server, so your data stays private, and it is free to use with no signup required.
Quick Answers
- Does error reporting show where the problem is?
- Yes. When JSON is invalid, the validator reports the line and character position from the parser, so you immediately know where to fix the document.
- Can I validate a JSON Lines (NDJSON) file?
- For JSON Lines documents use the JSON Lines / NDJSON Formatter elsewhere on this site, which validates each line and reports the exact line number that fails.
- Is my JSON uploaded anywhere?
- No. All validation runs locally in your browser. Nothing is sent to any server.
How to use JSON Validator & Checker
- Paste your JSON into the input box.
- A validation report appears instantly — valid or an exact error message.
- Copy the report or download it as a text file.
Why use our json validator & checker?
Incorrect or malformed JSON is the most common cause of broken API calls, config files and data pipelines. This validator reads your input with a strict JSON parser and returns one of two results: "Valid JSON" with a quick summary (type, number of items or keys, byte size) and a pretty-printed preview, or an "Invalid JSON" message that points at the exact line and character position where the parse fails. Because parsing happens entirely in the browser, you can safely validate configuration files, authentication payloads and test fixtures without uploading them to a server.
How a JSON validator reads your document
A validator does more than answer yes or no. It parses the document, verifies every comma, quote and brace, reports where a problem occurred, and can show summaries that a human glosses over.
| Aspect | Manual eyeballing | Validator output |
|---|---|---|
| Detection | Slow, misses subtle mistakes in large files | Instant, reports the first error precisely |
| Error location | Approximate — you scan visually | Exact line and character position |
| Confirmations | Assumes valid until something breaks | Explicit Valid JSON confirmation with summary |
| Too-large files | Impractical to verify by eye | Parsed correctly regardless of size |
| Result | Unknown until the consumer fails | Known before the API/config is shipped |
Finding the broken comma before the API call fails
Copying JSON between tools often introduces a stray comma or a missing quote. This is exactly what the validator catches — and it tells you the position, not just 'invalid'.
JSON with a mistake
{
"user": "ada",
"role": "analyst",
"tags": ["json", "csv", "api",],
"active": true
}Validation report
Invalid JSON: Unexpected token ], ... is not valid JSON (around character 62).
A trailing comma inside an array is the usual cause. Remove it and paste the JSON again to get the full report:
Valid JSON ✔
Type: object
4 key(s)
Size: 96 bytes
Formatted:
{ ... }Paste any JSON from Postman, a config file, or a teammate's email before pasting it into code — the validator pinpoints the exact character so you fix it in seconds.
Frequently Asked Questions
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