JSON validator online
Validate JSON syntax instantly and find errors in malformed JSON. View validation results and useful error details directly in your browser without uploading your data.
All Developer Tools
Browse free online tools for JSON, HTML, CSS, XML, JavaScript, data conversion, and everyday development tasks.
Try a different search term or select another category.
What Is a JSON Validator?
A JSON validator is a tool that checks whether text follows the syntax rules of JavaScript Object Notation (JSON). It checks the arrangement of braces, brackets, quotation marks, commas, colons, keys, and values so you can identify problems before using the data in an application, API request, configuration file, or data pipeline.
JSON is a lightweight, text-based format for representing structured information. It supports objects, arrays, strings, numbers, boolean values, and null. Although JSON syntax resembles JavaScript object notation, standard JSON follows stricter rules: keys and strings need double quotes, comments are not permitted, and trailing commas are invalid.
Use this online JSON validator to inspect a JSON snippet, check a payload, or troubleshoot data copied from an API or configuration file. When the input is invalid, use the error details to find the likely problem, correct it, and validate the content again.
Important: Syntax validation checks whether the text is valid JSON. It does not automatically confirm that the data is accurate, secure, or suitable for your application.
How to Validate JSON Online
Checking a JSON document usually takes just a few steps. Start with the complete object or array you want to test, then review the validation result and fix any reported syntax problems.
Paste the JSON text into the editor, or select a JSON file if file upload is available in the tool. Include the complete value you want to check.
Choose the validation action, or review the automatic result if the editor checks your input as you type.
If the JSON is invalid, read the error message and check the reported line and column when available. The actual mistake may appear just before the reported position.
Check nearby commas, quotation marks, colons, and brackets. Run validation again after making the correction.
Once the JSON is valid, you can use it in your development workflow. If formatting or minifying controls are available, they can help you make valid JSON easier to read or more compact.
Example of Invalid JSON
The following example contains a trailing comma after the final array item. Standard JSON does not allow a comma immediately before a closing bracket.
Problem: The comma after "editor" is not allowed because it appears before the closing square bracket.
Corrected JSON
The corrected example removes the trailing comma. Its object, array, strings, and boolean value now follow standard JSON syntax.
Common JSON Errors and How to Fix Them
Small punctuation mistakes can make an otherwise readable JSON document invalid. Use this table to identify frequent syntax problems and their usual corrections.
| Error | Invalid example | How to fix it |
|---|---|---|
| Trailing comma | {"a": 1,} |
Remove the comma before the closing brace or bracket. |
| Single quotes | {'name': 'Ada'} |
Use double quotes for object keys and string values: {"name": "Ada"}. |
| Unquoted key | {name: "Ada"} |
Put double quotes around the key: {"name": "Ada"}. |
| Missing comma | {"a": 1 "b": 2} |
Add a comma between adjacent object properties or array items. |
| Missing colon | {"name" "Ada"} |
Place a colon between each key and its value. |
| Unclosed bracket | {"items": [1, 2} |
Close the array with ] before closing the object with }. |
| Comments | { // note } |
Remove JavaScript-style comments; standard JSON does not support comments. |
| Invalid value | {"value": undefined} |
Use a permitted JSON value such as a string, number, object, array, true, false, or null. |
| Invalid escape | {"path": "C:\new"} |
Escape a literal backslash, for example "C:\\new", and check that all escape sequences are valid. |
Error locations are useful clues, but a parser may report where it could no longer continue rather than where the original typo began. If an error points to a closing bracket, inspect the values and punctuation immediately before it.
JSON Syntax Validation vs. JSON Schema Validation
Syntax validation and schema validation answer different questions. Syntax validation checks whether the text can be parsed as JSON. Schema validation checks whether valid JSON follows an expected structure and set of rules.
Is this valid JSON?
A syntax validator checks quotation marks, separators, brackets, and legal JSON values.
The example is syntactically valid JSON, even if its values may not match an application's expectations.
Does it match the schema?
A JSON Schema can define required fields, expected data types, allowed values, text patterns, and numeric limits.
For example, a schema may require email to be a string and age to be an integer. The previous example would fail those rules even though its JSON syntax is valid.
Choose the right check: Use a JSON syntax validator to find malformed JSON. Use a JSON Schema validator as well when you need to enforce a particular data contract. Schema validation is available only if the tool provides that feature.
Why Use a JSON Validator?
JSON is commonly used to exchange structured information between applications and services. Validating it before use can help catch formatting mistakes early and reduce avoidable errors during development and testing.
Debug API Requests and Responses
Check request bodies, response payloads, and sample data before investigating an issue in the application that consumes them.
Review Configuration Files
Catch missing punctuation or malformed values before a program attempts to read its JSON settings.
Test Webhooks and Integrations
Inspect event payloads and integration data to make sure the text is well-formed JSON before using it in a workflow.
Prepare Test Fixtures
Check mock responses and test data so syntax errors do not interfere with QA checks or automated tests.
Inspect Exported Data
Validate JSON files produced by applications, reports, scripts, or data-processing tasks before importing them elsewhere.
Find Errors Faster
Use a parser's error message and line or column information, when available, to narrow down the location of a syntax problem.
JSON Rules to Remember
Keep these core syntax rules in mind when writing or troubleshooting JSON.
- Use double quotes: Object keys and string values must be enclosed in double quotation marks.
- Separate keys and values with a colon: Each object property follows the pattern
"key": value. - Separate items with commas: Use commas between object properties and array items, but not after the final item.
- Match your brackets: Objects use curly braces
{}, while arrays use square brackets[]. - Use supported value types: JSON values can be objects, arrays, strings, numbers,
true,false, ornull. - Do not use comments: Standard JSON does not allow
//or/* ... */comments. - Avoid JavaScript-only values:
undefined, functions,NaN, andInfinityare not valid standard JSON values. - Check escaping: Use valid escape sequences for quotation marks, backslashes, and special characters inside strings.
- Keep keyword spelling exact: The literals
true,false, andnullmust be lowercase.
Is This JSON Validator Private?
This validator is intended to check JSON in your browser, with the input processed locally rather than sent to a remote server for validation. Browser-side processing is convenient when inspecting examples, development payloads, or configuration data.
Even when a tool processes data locally, check your own browser extensions, device, and workflow before handling sensitive information. Avoid entering passwords, access tokens, private customer details, or production secrets unless you have verified that the environment is appropriate for them.
Security reminder: Validation does not encrypt data, remove sensitive fields, or make a payload safe to share. Review your JSON before copying, exporting, or sending it to another person or service.
Frequently Asked Questions
What is a JSON validator?
A JSON validator checks whether text follows standard JSON syntax. It helps identify problems such as missing commas, incorrect quotation marks, invalid values, and unmatched brackets.
How do I validate JSON online?
Paste your JSON into the editor and run the validation action. Review the result, correct any reported syntax errors, and validate the updated text again.
Is this JSON validator free?
The tool is presented as a free online JSON validator. Any usage limits or additional features depend on the options provided in the tool interface.
Can I validate a JSON file?
If file upload is enabled in the tool, select a JSON file to check its contents. Otherwise, open the file in a text editor and paste the JSON into the input area.
Does a JSON validator fix errors automatically?
A validator identifies syntax problems, but it does not necessarily fix them. Correct the reported issue yourself unless the tool explicitly provides an automatic repair feature.
Why does my JSON work in JavaScript but fail validation?
JavaScript object literals allow syntax that standard JSON does not, including single-quoted strings, unquoted property names, comments, trailing commas, and values such as undefined. Convert the input to strict JSON syntax before validating it.
What does a line and column error mean?
It indicates where the parser detected a syntax problem or where it could no longer continue reading the input. The original mistake may be slightly earlier, so inspect the surrounding punctuation and values.
Can valid JSON still contain incorrect data?
Yes. Syntax validation checks the JSON format, not whether the values are factually correct or appropriate for an application. Use additional validation rules or a schema when the data must follow a specific contract.
What is the difference between a JSON validator and a formatter?
A validator checks syntax. A formatter adds indentation and line breaks to make valid JSON easier to read. Some tools combine both functions.
Can JSON contain comments?
No. Standard JSON does not support single-line or multiline comments. Remove comments before parsing the text as JSON.
What is the difference between JSON syntax and JSON Schema?
JSON syntax defines how the text must be written. JSON Schema can describe the expected structure, required properties, data types, and allowed values. A schema check is separate from basic syntax validation.
Does validation change my JSON?
Validation reads and checks the input; it does not need to change the content. Formatting, minifying, or editing are separate operations when those options are provided.