Forge Json

Fix Invalid JSON Online - Find Syntax Errors Fast

Paste invalid JSON to find the parse error, fix the broken character, and rerun the same validator before formatting, diffing, or schema checks.

Paste your JSON → Get results instantly (no signup)

⚡ Instant resultsNo signupRuns in your browser
Try examples:

→ Validate this order payload against a small schema config.

{
"order_id": "ORD_1001",
"customer_email": null,
"total_amount": "42.50",
"currency": "USD",
"items": 2
}
Output✓
1{
2  "valid": false,
3  "errors": [
4    {
5      "field": "customer_email",
6      "message": "Expected string, received null"
7    },
8    {
9      "field": "total_amount",
10      "message": "Expected number, received string"
11    },
12    {
13      "field": "items",
14      "message": "Expected array, received number"
15    }
16  ]
17}

Love the result?

Use this exact pipeline in your app, backend, or LLM workflow.

No setup needed. Works with curl, Node, Python.

Uses example data. For edited input, copy from the playground.

Read integration guide

Works with:

  • Parser error debugging
  • Broken config files
  • LLM-generated JSON
  • API payload repair

Example: input → output

Fix invalid JSON

Invalid JSON usually fails for a small reason: a trailing comma, a comment, a missing quote, a bad number, or a bracket that disappeared during copy-paste. This page helps you find the syntax error quickly so the document can parse again.

Paste the broken JSON into the tool and run the validator. The result points to the first parse failure. Fix that character, rerun the check, and repeat until the payload is valid. Once the JSON parses, you can format it, compare it, convert it, or validate it against a schema.

How to fix invalid JSON online

  1. Paste the invalid JSON into the input panel.
  2. Run the validator and read the error location.
  3. Fix the first syntax problem the parser reports.
  4. Run the check again because one invalid character can hide later errors.
  5. When the JSON is valid, continue with formatting, cleanup, conversion, or schema validation.

This page uses the same engine as the JSON Schema Validator, but it is framed around parser-error repair rather than structural validation.

Common causes of invalid JSON

  • Trailing commas in arrays or objects.
  • Single-quoted strings copied from JavaScript.
  • Unquoted object keys such as {name: "Ada"}.
  • Comments from JSONC, TypeScript config files, or copied examples.
  • Invalid numbers such as NaN, Infinity, 5., or 007.
  • Missing closing braces after trimming a snippet.

If you are not sure whether the document is broken or just ugly, start with Check JSON Format. If you simply need a syntax pass/fail result, use Validate JSON Online.

What to do after fixing JSON

After the syntax passes, use the JSON Formatter to format JSON and remove cleanup noise. Use the JSON Diff Tool to compare the fixed payload with a previous version. Use the JSON to CSV Converter when the valid data needs to move into a spreadsheet.

If the payload must satisfy an API contract, required fields, or specific types, run the JSON Schema Validator after the JSON is valid.

Frequently asked questions

How do I fix invalid JSON?+

Run the validator, fix the first parser error it reports, and rerun the check. Repeat until the document parses cleanly.

What is the most common invalid JSON error?+

Trailing commas, single quotes, unquoted keys, comments, invalid numbers, and missing closing brackets are the most common syntax failures.

Can this repair JSON automatically?+

The page focuses on locating syntax errors clearly. Some cleanup steps can be handled after parsing, but invalid syntax should be fixed deliberately so data is not changed unexpectedly.

Why does the parser only show one error?+

JSON parsers stop at the first syntax failure because later characters may be interpreted incorrectly after the first broken token.

What comes after fixing invalid JSON?+

Once syntax is valid, format or clean the JSON, compare it with another version, convert it to CSV, or validate the structure with JSON Schema.

Related tools

Read more on the blog

Advanced usage (optional)

Schema Validation

v1.0.0
Validation
objectarraystringreversible

Description

Schema Validation

Validate JSON against a JSON Schema-style subset and return a field-level report.

This utility is a report-producing transformer. It does not block, skip, warn, or otherwise control pipeline execution. Use validation.contract when a pipeline needs guardrail behavior.

Supported V1 Schema Fields

  • type: object, array, string, number, boolean, or null
  • required: array of required object keys
  • properties: object field rules
  • items: array item rule
  • enum: primitive values only, using strings, numbers, booleans, or null

Unknown fields are ignored in V1.

Invalid schema config returns:

{
  "valid": false,
  "errors": [
    { "field": "$schema", "message": "Missing or invalid schema config" }
  ]
}

Configuration

NameTypeDefaultDescription
Schema Configjson{"type":"object","required":[],"properties":{}}JSON Schema-style subset. Supports type, required, properties, items, and primitive enum values. Unknown fields are ignored in V1.

Examples

AI Prompt
Validate this order payload against a small schema config.
{
"order_id": "ORD_1001",
"customer_email": null,
"total_amount": "42.50",
"currency": "USD",
"items": 2
}
Output✓
1{
2  "valid": false,
3  "errors": [
4    {
5      "field": "customer_email",
6      "message": "Expected string, received null"
7    },
8    {
9      "field": "total_amount",
10      "message": "Expected number, received string"
11    },
12    {
13      "field": "items",
14      "message": "Expected array, received number"
15    }
16  ]
17}
Config
Schema Config
1{
2  "type": "object",
3  "required": [
4    "order_id",
5    "customer_email",
6    "total_amount",
7    "currency",
8    "items"
9  ],
10  "properties": {
11    "order_id": {
12      "type": "string"
13    },
14    "customer_email": {
15      "type": "string"
16    },
17    "total_amount": {
18      "type": "number"
19    },
20    "currency": {
21      "type": "string",
22      "enum": [
23        "USD",
24        "EUR",
25        "GBP"
26      ]
27    },
28    "items": {
29      "type": "array",
30      "items": {
31        "type": "object",
32        "required": [
33          "sku",
34          "qty"
35        ],
36        "properties": {
37          "sku": {
38            "type": "string"
39          },
40          "qty": {
41            "type": "number"
42          }
43        }
44      }
45    }
46  }
47}

API Usage

POST /api/v1/utilities/validation.schema
Example:
curl -X POST https://your-domain.com/api/v1/utilities/validation.schema \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"inputs":{"primary":{"order_id":"ORD_1001","customer_email":null,"total_amount":"42.50","currency":"USD","items":2}},"config":{"schema":{"type":"object","required":["order_id","customer_email","total_amount","currency","items"],"properties":{"order_id":{"type":"string"},"customer_email":{"type":"string"},"total_amount":{"type":"number"},"currency":{"type":"string","enum":["USD","EUR","GBP"]},"items":{"type":"array","items":{"type":"object","required":["sku","qty"],"properties":{"sku":{"type":"string"},"qty":{"type":"number"}}}}}}}}'
Response
1{
2  "valid": false,
3  "errors": [
4    {
5      "field": "customer_email",
6      "message": "Expected string, received null"
7    },
8    {
9      "field": "total_amount",
10      "message": "Expected number, received string"
11    },
12    {
13      "field": "items",
14      "message": "Expected array, received number"
15    }
16  ]
17}