JSON Parse Error?
Pinpoint and fix JSON.parse() errors instantly. See the exact line, column and cause of every syntax error — then auto-repair with one click.
Debugging JSON Parse Errors
Step-by-step approach to finding and fixing parse failures in your code.
Always Log the Raw Input
Before calling JSON.parse(), log the raw string. Many parse errors come from receiving HTML error pages, empty bodies, or already-parsed objects instead of JSON strings.
Check Content-Type Headers
If your API response has Content-Type: text/html, you are likely receiving an error page, not JSON. Check your API endpoint URL and authentication credentials.
Watch for Double Parsing
If your HTTP client (axios, fetch) auto-parses JSON responses, calling JSON.parse() again will fail. Check whether your data is already an object before parsing it.
Handle Edge Cases in Code
Always wrap JSON.parse() in a try-catch block. Check for empty strings and null values before parsing. Return a sensible default or error object when parsing fails.
Parse Error Diagnosis
Go from cryptic error messages to a working JSON document in seconds.
Exact Error Pinpointing
See the exact line, column and character that caused the parse failure. The editor highlights the error location so you do not have to search.
Human-Readable Error Messages
Instead of cryptic 'Unexpected token < at position 0' messages, get clear explanations like 'Expected double quote but found single quote at line 3'.
Auto-Fix Common Parse Errors
One-click repair for trailing commas, single quotes, comments and unquoted keys — the four most common causes of JSON.parse() failures.
Understanding JSON Parse Errors
JSON.parse() errors are among the most common runtime exceptions in JavaScript applications. They occur whenever the input string does not conform to the strict JSON specification. Understanding the error message pattern helps you diagnose the root cause without guessing.
Error Message Cheat Sheet
'Unexpected token <' — you received HTML instead of JSON (check the URL)
'Unexpected end of input' — the response was truncated (check the network)
'Unexpected token o at position 1' — you are parsing an already-parsed object
JSON Parse Error — FAQ
What does 'Unexpected token' mean in JSON.parse()?
It means the parser encountered a character it did not expect at a specific position. For example, 'Unexpected token <' usually means you received an HTML error page instead of JSON. 'Unexpected token ,' means a trailing comma or double comma.
What does 'Unexpected end of JSON input' mean?
The JSON string was cut off before the parser found all closing brackets and braces. Common causes: a truncated API response due to a network timeout, a string that was accidentally sliced, or a file that was not fully downloaded.
Why do I get 'Unexpected token o at position 1'?
This almost always means you called JSON.parse() on an object that was already parsed. The string representation of an object is '[object Object]', and the 'o' at position 1 triggers the error. Check if you are double-parsing.
How do I fix 'SyntaxError: JSON.parse' in my code?
First, log the raw string you are trying to parse. Paste it into this validator to see the exact error. Common code fixes: check that your API actually returns JSON (not HTML), verify Content-Type headers, and ensure the response body is not empty.
Why does JSON.parse fail on my API response?
Check three things: (1) the response Content-Type should be application/json, not text/html, (2) the response body should not be empty (status 204 or error pages), and (3) the server should not be returning JSONP (callback wrapper) instead of plain JSON.
Can I parse JSON with comments?
Standard JSON.parse() rejects comments. If your data contains // or /* */ comments, strip them first. This tool can remove comments automatically during the auto-fix process, producing valid JSON that JSON.parse() accepts.
What is the difference between JSON and a JavaScript object?
JSON requires double-quoted keys and strings, no trailing commas, no comments, and no undefined values. JavaScript objects allow all of these. JSON is a strict subset of JavaScript object literal syntax — every JSON document is valid JS, but not every JS object is valid JSON.
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