How do I know if my JSON is valid?

Paste it into the validator. Valid JSON gets a green “Valid JSON” result with statistics such as depth and number of keys. Invalid JSON shows the exact line and column of the problem, highlighted in the editor.

Can the validator fix my JSON?

Yes, for the common cases: trailing commas, single quotes, unquoted property names, comments, missing commas, True/False/None and undefined. Choose Try to repair to see what would change, then Use repaired JSON.

Which JSON standard is checked?

Strict JSON as defined in RFC 8259 — the format every JSON parser accepts. Extensions like JSON5 or JSONC (comments, trailing commas) are reported as errors, because many systems reject them.

Is my JSON sent to a server?

No. Validation and repair run entirely in your browser, so API keys or personal data in your JSON stay private.

JSON Validator

Check whether JSON is valid, see exactly where it breaks, and repair common mistakes in one click.

JSON input


{
  "name": "Weather API",
  "version": 3,
  "endpoints": [
    { "path": "/forecast", "method": "GET" },
    { "path": "/alerts", "method": "GET", },
  ],
  "auth": {
    type: "apiKey",
    "header": 'X-API-Key'
  }
}

Validation result

Invalid JSON

Error on line 6, column 41: Trailing comma: remove the ',' before '}'.

    { "path": "/alerts", "method": "GET", },
                                        ^

Repair JSON automatically

Fixes trailing commas, single quotes, unquoted keys, comments, True/False/None and other common mistakes.

How to validate JSON

Paste JSON on the left, or open or drop a .json file.
The result updates as you type: Valid JSON with statistics, or the exact line and column of the first error, highlighted in red.
Click Go to error to jump to the problem, or Try to repair to fix common mistakes automatically.

A strict JSON syntax checker

The validator checks your input against the JSON standard (RFC 8259) — the same rules every JSON parser enforces. Unlike a browser's built-in error (“Unexpected token} in JSON at position 212”), it tells you the line, the column and what to change, in the same words in every browser.

When the JSON is valid, you also see its structure at a glance: the top-level type, nesting depth and how many objects, arrays and keys it contains.

Common JSON errors this checker finds

Error	Example	Fix
Trailing comma	`{"a": 1,}`	Remove the comma before } or ].
Single quotes	`{'a': 'b'}`	Use double quotes: {"a": "b"}.
Unquoted key	`{a: 1}`	Quote property names: {"a": 1}.
Comment	`{"a": 1 // note}`	JSON has no comments — remove them.
Python/JS values	`{"a": None, "b": undefined}`	Use null (and true/false in lower case).

Automatic JSON repair

JSON copied from JavaScript code, Python output or hand-edited config files often has the same few problems. The repair feature fixes them and lists each change, so you stay in control:

Before

{name: 'Ada', active: True, tags: ['x',],}

After repair

{
  "name": "Ada",
  "active": true,
  "tags": [
    "x"
  ]
}

Related tools

Once your JSON is valid, make it readable with the JSON formatter or compact with the JSON minifier, or keep editing it in the online JSON editor. Checking other formats? Use the YAML validator for config files and the XML validator for XML.

Frequently asked questions

How do I know if my JSON is valid?: Paste it into the validator. Valid JSON gets a green “Valid JSON” result with statistics such as depth and number of keys. Invalid JSON shows the exact line and column of the problem, highlighted in the editor.
Can the validator fix my JSON?: Yes, for the common cases: trailing commas, single quotes, unquoted property names, comments, missing commas, True/False/None and undefined. Choose Try to repair to see what would change, then Use repaired JSON.
Which JSON standard is checked?: Strict JSON as defined in RFC 8259 — the format every JSON parser accepts. Extensions like JSON5 or JSONC (comments, trailing commas) are reported as errors, because many systems reject them.
Is my JSON sent to a server?: No. Validation and repair run entirely in your browser, so API keys or personal data in your JSON stay private.