It is a JSON linter that reports syntax errors. Same purpose as the original jsonlint tool, runs entirely in your browser.

No — only syntax. JSON has no formal style guide for linting.

100% browser-based · No data leaves your device

JSON Lint

Lint JSON for syntax errors. Reports invalid syntax, unexpected tokens, and structural issues with line numbers — the same way the original jsonlint does, but entirely in your browser.

JSON input

Validation result

Options

Show parsed outputInclude pretty-printed JSON when valid Show error snippetInclude 3 lines of context around the error Auto-validateRe-run on every input change

Open in formatter

Input size

0 B

Lines

Errors

Status

Ready

Example

Valid vs invalid JSON

Strict JSON requires double-quoted keys, no trailing commas, and no comments. Anything else fails the parser — and the validator pinpoints the spot.

Valid

{
  "name": "hcodx",
  "version": 1,
  "tags": ["dev", "tools"]
}

Invalid — trailing comma at line 4

{
  "name": "hcodx",
  "version": 1,
  "tags": ["dev", "tools"],
}

Use cases

What you'll use this for

Anywhere strict JSON is consumed: HTTP APIs, configuration files, log lines, CI pipelines, database documents.

API debugging

Paste a response body, find the malformed key or stray comma before your client crashes on it.

Config file checks

Validate package.json, tsconfig.json, or any app config before committing.

Webhook payloads

Confirm the payload your service produces is parseable everywhere downstream.

NoSQL documents

Verify Mongo / DynamoDB documents before bulk insert.

Step by step

How to validate JSON

Paste your JSON

Drop it into the left editor. CodeMirror highlights syntax as you type.

Click Validate

Or leave auto-validate on for live feedback. The parser runs locally — no server.

Read the report

If valid you'll see a tick plus the parsed object pretty-printed. If invalid you'll see the line, column, and a snippet around the error.

Fix and re-run

Edit the input, re-validate. Auto-validate keeps the report fresh while you type.

FAQ

Frequently asked questions

Is this jsonlint?

It's a JSON linter that reports syntax errors — the same purpose as the original jsonlint tool. The engine here is the browser's built-in JSON.parse, so the results are identical to anywhere else your JSON gets parsed.

Does it lint style?

No — only syntax. JSON has no formal style guide; for indentation and key ordering use the JSON formatter instead.

Is it free?

Yes. Completely free, no signup, no limits, no ads.

Does it leave the browser?

No. Pure client-side. Your data never leaves your device.

What about JSON5 or JSONC?

Strict JSON only here. For JSON5 (comments, unquoted keys, trailing commas) use the JSON5 formatter.

About

About this validator

JSON is the most common interchange format on the web — but parsers are strict. A misplaced comma, an unquoted key, or a stray character will reject the whole document. This validator gives you fast, line-precise feedback so you don't lose time hunting.

What it checks

Quotes — keys and string values must use " (double quotes).
Commas — between items, no trailing commas in arrays or objects.
Brackets — every { and [ needs a matching } / ].
Escapes — \n, \t, \", \\, \uXXXX are valid; unknown \ sequences fail.
Primitives — true, false, null (case-sensitive), plus IEEE-754 numbers.

Why use a browser validator

Private. Production secrets in your JSON never leave the device.
Fast. No round-trip; results appear as you type.
Honest. Uses the same JSON.parse implementation your Node.js / browser app uses, so a pass here is a pass everywhere.