JSON Validator

How to use JSON Validator

Three simple steps, with your content kept on your device.

Built for useful work

Fast, focused, and made to be clear on every screen.

What is JSON validation?

Validating JSON means checking that a piece of text follows the JSON specification exactly: objects wrapped in curly braces, arrays in square brackets, every key and string in double quotes, and values separated by commas with no trailing comma after the last entry.

A valid document is the prerequisite for everything else — parsing it, storing it, or sending it to an API. This tool runs that check with the browser's native JSON parser, so the verdict matches what a real runtime will accept.

What this validator reports

Beyond a valid or invalid verdict, the report shows four structural facts: the root type (object, array, string, number, boolean, or null), the number of top-level entries, the total number of values in the whole document, and the maximum nesting depth.

Those numbers are useful for spotting unexpected shapes — an API response that should be an array, a config file that suddenly has hundreds of entries, or deeply nested data that could trip a parser with a depth limit.

Validation vs formatting

A validator answers one question: is this valid JSON? It does not change the input. A formatter, like the separate JSON Formatter tool, pretty-prints or minifies the data, which necessarily rewrites it.

If you only need a yes-or-no check plus structural details, use this tool. If you want a readable or compact version of your JSON, run it through JSON Formatter.

Common invalid JSON examples

The most frequent mistakes are a missing comma between values, a trailing comma after the final entry, keys without double quotes, strings wrapped in single quotes, comments, and unescaped control characters such as a raw null byte.

The validator reports the location of the error and rejects raw control characters explicitly, because they break parsing in ways that are easy to miss.

How Valestiom handles your data locally

Validation runs entirely in the current browser tab. The input is measured in bytes, parsed locally, and analyzed without any network request — no upload, no account, no stored copy.

That makes it safe to check configuration files, API payloads, and any other JSON you prefer to keep off third-party servers.

How to validate JSON online

To validate JSON online, paste the document into the input area and read the result. The validator parses the text and reports either that it is valid or the exact location of the first problem.

This page works as a json lint and validation tool in one: it checks syntax, confirms the root type, and reports the number of entries and nesting depth — everything you need to know that a JSON document is structurally sound before using it.

Reading syntax error reports

When JSON is invalid, the error message points at the problem — a missing comma, an unclosed brace, a trailing comma, or a stray quote. Fixing the reported position usually resolves the document.

A validator is the fastest way to debug JSON from hand-written config files, API responses, or exported data, because it replaces guesswork with a precise location.

Validating JSON in development workflows

Developers validate JSON constantly: before committing a config file, after receiving an API response, or while debugging why a parser rejected a payload. A local validator makes each of these checks instant.

Because the check runs entirely in the browser, sensitive payloads can be validated without uploading them anywhere — a real advantage over web services that receive your document.

Using the structural report

Beyond pass or fail, the tool reports the root type (object, array, string, number, boolean, or null), the number of top-level entries and values, and the nesting depth. These numbers reveal the shape of the document at a glance.

A quick depth and entry report is useful before transforming JSON — it tells you whether you are dealing with a flat list, a nested record, or something unexpectedly deep.

Frequently asked questions