Forge Json

Validate JSON Online - Free Syntax Checker

Paste a JSON document to validate JSON online, catch parser errors, and add schema checks when the payload needs a stricter contract.

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:

  • JSON files and snippets
  • API request bodies
  • Webhook samples
  • Optional JSON Schema validation

Example: input → output

Validate JSON online

Use this page when the task is direct: validate JSON online and find out whether the document parses. Paste a file, API body, webhook sample, config snippet, or LLM-generated response into the tool and run the check. If the syntax is valid, you can format, clean, diff, convert, or validate the structure with a schema.

This page uses the same validation engine as the main JSON Schema Validator, but the intent is simpler. You do not need to start with a schema. First, confirm the JSON is valid. Then add schema rules only when the payload must match a contract.

How to validate JSON online

  1. Paste JSON into the input panel.
  2. Run the validator.
  3. If the parser reports an error, use the line and column to fix the document.
  4. Run it again until the syntax passes.
  5. Add optional schema rules when you need required fields, expected types, or enum checks.

This flow catches the common problems that break JSON parsers: trailing commas, single quotes, unquoted keys, comments, bad numbers, and mismatched brackets.

When this page is the right fit

  • You copied JSON from a log, chat, browser console, or API response and want a quick check.
  • A backend endpoint rejected a payload and you need to validate JSON online before retrying.
  • A config file looks right but a parser says it is invalid.
  • You want to confirm syntax before using the JSON Formatter, JSON Diff Tool, or JSON to CSV Converter.

If the JSON parses but the shape is wrong, switch to the JSON Schema Validator for structure validation.

Validate JSON online vs check JSON format

"Validate JSON online" usually means "does this parse?" It is a syntax-first workflow. "Check JSON format" is slightly more presentation-oriented: it catches invalid syntax and helps you confirm that the text is ready to share, import, or paste into code.

Both pages use the same live tool. The difference is intent. Use Check JSON Format when you are preparing a document for handoff. Use Fix Invalid JSON when you already know the parser is failing and need to locate the broken character. Use JSON Lint when the workflow is a review pass before commit, import, or API handoff.

Frequently asked questions

Can I validate JSON online without a schema?+

Yes. Paste JSON and run the syntax check first. A schema is optional and only needed when you want to validate required fields, types, or other structural rules.

What errors does online JSON validation catch?+

It catches parser errors such as trailing commas, single quotes, unquoted keys, comments, invalid numbers, control characters, and mismatched brackets.

Is my JSON uploaded?+

The validation runs in your browser for ad-hoc checks. Use it for quick syntax validation before moving the payload into a backend, API, or pipeline workflow.

What should I do after the JSON validates?+

You can format it, clean it, compare it with JSON Diff, convert it to CSV, or add a JSON Schema when the payload must match a contract.

Is this different from JSON Schema validation?+

Syntax validation checks whether the text parses as JSON. JSON Schema validation checks whether already-valid JSON matches a required structure.

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}