JSON & Data· Updated 2026-08-30· 3 min read

JSON.parse() Error Messages: Causes, Examples & Fixes

Modern browsers provide descriptive error messages when JSON.parse() fails. This reference table translates common error strings into clear root causes and solutions.

Parser Error Lookup Table

Table: Common JavaScript JSON.parse() exceptions and their direct fixes.
Error Message	Typical Cause	Verified Solution
Unexpected token < in JSON at position 0	Server returned HTML error page instead of JSON	Check API status code; inspect if response is HTML error
Unexpected token } in JSON at position X	Dangling trailing comma before closing brace	Remove trailing comma from the last property
Unexpected token ' in JSON at position X	Single quotes used instead of double quotes	Replace single quotes with double quotes around keys/values
Unexpected number in JSON at position X	Missing comma between object properties	Add comma separator between key-value pairs
Bad escaped character in JSON at position X	Invalid backslash escape (e.g. Windows path \U)	Double-escape backslashes as \\
Unexpected end of JSON input	Empty string or truncated/incomplete response stream	Verify payload was received in full; check network buffer

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JSON Validator

Open JSON Validator

Check single-quote errors and identify unexpected tokens.

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{
  "error": 'unauthorized'
}

JSON & Data· Updated 2026-08-30· 3 min read

JSON.parse() Error Messages: Causes, Examples & Fixes

Modern browsers provide descriptive error messages when JSON.parse() fails. This reference table translates common error strings into clear root causes and solutions.

Parser Error Lookup Table

Table: Common JavaScript JSON.parse() exceptions and their direct fixes.
Error Message	Typical Cause	Verified Solution
Unexpected token < in JSON at position 0	Server returned HTML error page instead of JSON	Check API status code; inspect if response is HTML error
Unexpected token } in JSON at position X	Dangling trailing comma before closing brace	Remove trailing comma from the last property
Unexpected token ' in JSON at position X	Single quotes used instead of double quotes	Replace single quotes with double quotes around keys/values
Unexpected number in JSON at position X	Missing comma between object properties	Add comma separator between key-value pairs
Bad escaped character in JSON at position X	Invalid backslash escape (e.g. Windows path \U)	Double-escape backslashes as \\
Unexpected end of JSON input	Empty string or truncated/incomplete response stream	Verify payload was received in full; check network buffer

Interactive Tool

JSON Validator

Open JSON Validator

Check single-quote errors and identify unexpected tokens.

Preset Payload

{
  "error": 'unauthorized'
}