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Fix JSON.parse() Error in JavaScript

Complete guide with error handling examples

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JavaScript · JSON.parse

JSON.parse() is one of the most commonly used JavaScript functions, but it throws errors when given invalid JSON. Learning how to handle these errors properly is essential for robust applications.

In this guide, we'll show you how to fix JSON.parse() errors in JavaScript, with proper error handling examples and our free JSON Fixer toolto validate JSON before parsing.

Common JSON.parse() Errors

SyntaxError: Unexpected token } in JSON

Usually caused by trailing commas or syntax errors.

SyntaxError: Unexpected end of JSON input

JSON is incomplete or missing closing braces. See the full guide.

SyntaxError: Unexpected token < in JSON

HTML was returned instead of JSON (API error).

Proper Error Handling with Try-Catch

Always wrap JSON.parse() in a try-catch block:

try {
  const jsonString = '{"name": "John", "age": 30}';
  const data = JSON.parse(jsonString);
  console.log(data);
} catch (error) {
  if (error instanceof SyntaxError) {
    console.error('Invalid JSON:', error.message);
    // Use JSON Fixer to fix it
  } else {
    console.error('Unexpected error:', error);
  }
}

Validate JSON Before Parsing

Validate JSON using our free JSON Validator before parsing:

💡 Best Practice:

  1. Validate JSON using our JSON Validator
  2. If invalid, use our JSON Fixer to repair it
  3. Then parse the fixed JSON in your code

Fix JSON.parse() Errors Instantly — Try It Below

Paste your broken JSON and our fixer will repair it for safe use with JSON.parse().

Advanced JSON Fixer & Recovery Engine

Paste → Instant fix. Repair malformed JSON: trailing commas, missing quotes, broken arrays, AI-generated JSON — 100% client-side

Repair options

Fix from API error

Paste an error like "Unexpected token } in JSON at position 245" to highlight the position.

or paste JSON below

JSON Input

1
1

Fixed JSON Output

Fixed JSON will appear here...

JSON Fixer Features

Automatic Error Detection

Scans and identifies all JSON syntax errors automatically

Smart JSON Repair

Fixes common errors like trailing commas, single quotes, and unquoted keys

Precise Error Location

Shows exact line and column numbers for each error

Visual Error Highlighting

Highlights problematic lines with color-coded indicators

Fix JSON.parse() Errors in JavaScript

The JavaScript error SyntaxError: Unexpected token ... in JSON at position X is thrown by JSON.parse() when the string you pass is not valid JSON. Common causes include: passing undefined or null (which stringify to the string "undefined" — not valid JSON), getting a 404 or 500 HTML error page from a fetch() call instead of a JSON body, double-encoding (a JSON string nested inside another), or a truncated response that ends before the closing bracket.

Paste the broken JSON string into the fixer above to see exactly where the parser fails. The tool highlights the problematic character and offers one-click auto-fix for common structural issues.

How to fix

Fix This JSON Error in Seconds

01

Paste your broken JSON

Paste the JSON string that caused the JSON.parse() error into the fixer above.

02

Error is highlighted

The tool shows the exact position where the parser stopped and what it found.

03

Click Auto-Fix

The auto-fixer repairs structural issues — missing brackets, trailing commas, and more.

04

Copy fixed JSON

Copy the valid JSON output to use safely with JSON.parse() in your code.

FAQ

Frequently Asked Questions

1What are the most common JSON.parse() errors in JavaScript?
The most common are: passing undefined or null to JSON.parse(), receiving an HTML error page (404/500) instead of JSON, double-encoded JSON (a JSON string inside another JSON string), and truncated API responses. All of these throw SyntaxError.
2How do I debug when fetch returns HTML instead of JSON?
Check the response Content-Type header and HTTP status before calling .json(). If status is 404 or 500, the server returned an HTML error page. Use response.text() to inspect the raw body and confirm.
3How do I check if a response is JSON before parsing?
Check response.headers.get("content-type") — it should include "application/json". Also verify response.ok or response.status before calling response.json(). Always wrap JSON.parse() in a try/catch to handle unexpected errors gracefully.
Learn more

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