JSON Validator

Stop Guessing Why Your JSON Is Broken—Validate It Instantly

JSON syntax errors are among the most frustrating debugging experiences in web development because they fail completely and silently—a single misplaced comma or a forgotten closing bracket makes the entire payload unparse-able, and the error message from many JSON parsers (`Unexpected token at position X`) tells you where the parser gave up, not necessarily where the actual mistake is. Our free JSON validator parses your input against the full JSON specification and either confirms it's valid or provides a specific, actionable error message pointing to the exact location of the problem.

Paste your JSON and click Validate. Valid JSON gets a confirmation and the option to view it formatted. Invalid JSON gets a specific error message identifying what went wrong and, where possible, the line number or character position where the issue was detected. No more scanning through hundreds of lines of minified JSON looking for a rogue trailing comma—the validator finds it immediately.

The Most Common JSON Syntax Errors

Most JSON validation failures fall into a small number of recurring categories. Understanding these patterns helps you recognize and fix them faster—and understand the validation error messages when you see them.

Trailing Commas

This is by far the most common JSON syntax error, particularly among developers who are used to writing JavaScript where trailing commas in object literals and arrays are permitted. JSON does not allow a comma after the last element in an array or the last key-value pair in an object. `{"name": "Alice", "age": 32,}` is invalid JSON because of the comma after `32`. `[1, 2, 3,]` is invalid because of the comma after `3`. The fix is simply to remove the trailing comma.

Unquoted or Single-Quoted Keys

JavaScript object literal syntax allows unquoted keys (`{name: "Alice"}`) and single-quoted keys (`{'name': 'Alice'}`). JSON does not. All JSON object keys must be enclosed in double quotes. `{"name": "Alice"}` is valid JSON. `{name: "Alice"}` and `{'name': 'Alice'}` are not. If your JSON was generated from JavaScript object literal syntax without going through `JSON.stringify()`, this is a likely cause of validation failures.

Unescaped Special Characters in Strings

Certain characters inside JSON string values must be escaped with a backslash to be valid. These include double quotes (`\"`), backslashes (`\\`), and control characters like newlines (`\n`) and tabs (`\t`). A string value containing an unescaped newline character—which happens when a multi-line string is pasted directly into a JSON value—will fail validation. The fix is to replace literal newlines in string values with the escaped `\n` sequence.

Mismatched or Missing Brackets and Braces

Every opening `{` needs a matching closing `}`. Every opening `[` needs a closing `]`. When these are missing or mismatched—usually due to manual editing errors in complex nested structures—the parser reaches the end of the file or encounters an unexpected character where it expected a closing delimiter. The validator identifies the position where the mismatch was detected, which combined with a visual inspection of the surrounding structure usually points to where a bracket was added or deleted.

Comments in JSON

JSON does not support comments. Neither `// line comment` nor `/* block comment */` syntax is valid in JSON, even though both are valid in JavaScript. If you've inherited a JSON file that someone added comments to for documentation purposes, those comments must be removed before the file can be parsed as valid JSON. Some tools use JSON5 (a superset of JSON that does support comments) for configuration files, but standard JSON parsers will reject anything with comment syntax.

JSON Validation vs. JSON Schema Validation

Our tool validates JSON syntax—it checks that your JSON follows the structural rules of the JSON specification and can be parsed into a valid data structure. This is different from JSON Schema validation, which validates that a parsed JSON value conforms to a specific expected shape, type constraints, and value requirements defined by a schema document.

Syntax validation answers the question: "Is this valid JSON that can be parsed?" Schema validation answers the question: "Does this JSON have the right structure and values for my application?" Both are important in different contexts. Syntax validation is always the prerequisite—schema validation can only happen on JSON that is syntactically valid first.

When to Validate JSON in Your Workflow

JSON validation is useful at several stages of a development or integration workflow. When writing JSON configuration files by hand, running them through the validator before deploying catches typos that would otherwise fail silently at runtime. When receiving API responses that are behaving unexpectedly, validating the raw response body confirms whether the parsing failure is a syntax issue in the response or a logic issue in how your code handles a valid response. When preparing JSON payloads to submit to an API that's returning cryptic errors, validation confirms your request body is syntactically sound before investigating authentication, endpoint, or parameter issues.

Private, Free, and Instant

The JSON validator runs entirely within your browser. No JSON data you paste in is transmitted to any server or stored anywhere outside your current session. The tool is completely free with no registration required. Validate any JSON payload—API responses, configuration files, database exports, request bodies—with confidence that your data never leaves your device.