How do I validate JSON in JavaScript?

Use a try/catch around JSON.parse(str). If it succeeds, the JSON is valid. If it throws SyntaxError, the JSON is invalid. Example: try { JSON.parse(str); } catch(e) { console.error("Invalid JSON:", e.message); }

What does JSON.parse throw for invalid JSON?

JSON.parse throws a SyntaxError with a message describing the problem. The message varies by browser/engine but typically includes "Unexpected token" and the character position.

Can I validate JSON in JavaScript without try/catch?

Not with the built-in JSON.parse — it always throws for invalid input. Some third-party libraries offer non-throwing parsers, but try/catch is the standard approach.

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Validate JSON in JavaScript

In JavaScript, JSON validation is done by attempting to parse the string with JSON.parse(). If it throws a SyntaxError, the JSON is invalid. You can wrap this in a try/catch to handle it gracefully. For quick manual checks — when you want to validate a snippet without writing code — FixTools validates JSON directly in your browser.

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How to use this tool

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Paste JSON from your JavaScript application and validate it without writing a try/catch.

How It Works

Step-by-step guide to validate json in javascript:

1
Write the validation in JavaScript
Use: function isValidJSON(str) { try { JSON.parse(str); return true; } catch { return false; } }
2
Or paste into FixTools for a manual check
For quick checks during development, paste the JSON string into FixTools and click Validate.
3
Handle the result
In your code, check the return value and handle the invalid case. In FixTools, read the error message and fix the JSON.