Is my JSON uploaded or stored?

No. The validator runs in your browser with local JSON.parse. The payload is not uploaded, logged, or stored by allthevalidators.com.

Why does a trailing comma make JSON invalid?

Strict JSON does not allow a comma before the closing } or ]. JavaScript and JSON5 may accept it, but APIs that expect JSON usually reject it.

Why are single quotes or unquoted keys invalid?

JSON strings and object keys must use double quotes. Snippets like {name:'Ada'} are JavaScript object literals, not valid JSON.

Does this validate against JSON Schema?

No. This page checks syntax only. Once the JSON parses, use a JSON Schema validator to confirm required fields, data types, and allowed values.

Can I validate an API response or webhook payload?

Yes. Paste the response body or webhook sample directly into the text area to catch syntax problems before debugging application-specific rules.

How big of a payload can I validate?

Small and medium payloads are best. The validator runs locally in the browser, so very large files may feel slow depending on your device.

format validator

JSON Validator & Syntax Checker

Check JSON syntax, catch trailing commas and quote errors, and keep every payload local to your browser.

Results

Paste input and validate locally.

Status: Ready when you validate.
Details: Ready when you validate.

How to use this validator

Paste the JSON payload that is failing in your API client, config file, webhook sample, or test fixture.
Run the validator to parse it locally with the browser's strict JSON parser.
If the payload fails, check the token mentioned in the error and inspect the character just before it for a missing comma, quote, bracket, or escape.
After the syntax check passes, move on to JSON Schema or application-specific validation if you need to verify required fields and types.

Rules & checks

Runs strict JSON.parse syntax validation in your browser; no uploads, logs, or server-side parsing.

Catches the errors developers hit most often: trailing commas, single-quoted strings, unquoted keys, missing commas, bad escapes, and unexpected tokens.

Accepts standard JSON only. Comments, JSON5 features, JavaScript object literals, and trailing commas should be removed before validation.

Returns clear pass/fail details for pasted API payloads, package/config snippets, CMS exports, and webhook examples.

Inputs explained

JSON payload
Paste a complete JSON object, array, string, number, boolean, or null. For best browser performance, keep pasted payloads under a few hundred KB.

When to use it

Debug API request and response bodies before sending them to a server
Validate webhook samples from Stripe, GitHub, Slack, Shopify, or internal systems
Check package, app, CMS, or CI config snippets before committing them
Confirm fixtures and mock data are strict JSON before using them in tests
Pre-flight a payload before running JSON Schema validation or diff/formatting tools

Common errors

Trailing commas after the last item in an object or array
Single quotes around strings instead of JSON's required double quotes
Unquoted property names copied from JavaScript examples
Missing commas between object properties or array items
Unescaped backslashes, tabs, newlines, or quotation marks inside strings
Comments copied from JSON5, TypeScript, or config examples

Limitations

Syntax-only: it confirms the JSON can parse, but it does not enforce required fields, enum values, or business rules.
Strict JSON only: comments, trailing commas, single quotes, undefined, NaN, and Infinity are invalid.
Very large payloads can slow the browser because validation happens locally on your device.
Does not fetch remote URLs or inspect API endpoints; paste the content directly.

Tips

If the error mentions an unexpected token, inspect the character immediately before that token; the real mistake is often the previous comma or quote.
Do not paste JavaScript object literals directly—convert single quotes, comments, undefined, and unquoted keys to strict JSON first.
Use the JSON prettifier after a valid parse when you need readable indentation for review or documentation.
For payloads with required fields, first pass this syntax check, then run a JSON Schema validator for field-level rules.

Examples

Valid: API response object

{"id":101,"user":{"name":"Ada","active":true},"roles":["admin","editor"]} -> Valid JSON

Valid: array of records

[{"sku":"A-100","qty":3},{"sku":"B-200","qty":1}] -> Valid JSON

Invalid: trailing comma

{"name":"Ada",} -> Invalid because strict JSON cannot include a comma before the closing brace

Invalid: JavaScript object literal

{name:'Ada'} -> Invalid because JSON requires quoted keys and double-quoted strings

Deep dive

This JSON validator is built for the errors that break API payloads, webhook fixtures, and config files: trailing commas, single quotes, unquoted keys, missing separators, and escaped-character mistakes. Because the check runs in your browser, sensitive payloads never need to leave your machine just to confirm syntax.

Strict JSON is narrower than JavaScript object literals and JSON5. If a snippet contains comments, undefined, single-quoted strings, or a comma before the closing brace, this tool will flag it so the payload matches what JSON.parse, most APIs, and production services expect.

For a complete workflow, validate syntax first, prettify the JSON for review, then use a JSON Schema validator when you need to verify required properties, field types, or business-specific rules.

FAQs

Is my JSON uploaded or stored?: No. The validator runs in your browser with local JSON.parse. The payload is not uploaded, logged, or stored by allthevalidators.com.
Why does a trailing comma make JSON invalid?: Strict JSON does not allow a comma before the closing } or ]. JavaScript and JSON5 may accept it, but APIs that expect JSON usually reject it.
Why are single quotes or unquoted keys invalid?: JSON strings and object keys must use double quotes. Snippets like {name:'Ada'} are JavaScript object literals, not valid JSON.
Does this validate against JSON Schema?: No. This page checks syntax only. Once the JSON parses, use a JSON Schema validator to confirm required fields, data types, and allowed values.
Can I validate an API response or webhook payload?: Yes. Paste the response body or webhook sample directly into the text area to catch syntax problems before debugging application-specific rules.
How big of a payload can I validate?: Small and medium payloads are best. The validator runs locally in the browser, so very large files may feel slow depending on your device.

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