JSON Unexpected Token Error Fix

Unexpected token errors mean the parser found a character that is not valid at that position. Often the input is not JSON at all.

Symptoms

  • JSON.parse throws Unexpected token.
  • The token is <, which often means HTML was returned.
  • API client fails while browser shows an error page.

Likely causes

  • Server returned HTML instead of JSON.
  • JSON contains comments, trailing commas or single quotes.
  • Content-Type or endpoint URL is wrong.

Fix steps

  1. Inspect the raw response body before parsing.
  2. Check status code and Content-Type.
  3. Validate the JSON payload or response sample.

Verify the fix

  • Reproduce with curl -i.
  • Confirm response starts with { or [ for JSON APIs.
  • Handle non-2xx responses before JSON.parse.

FAQ

What does Unexpected token < mean?

It often means HTML was parsed as JSON, such as a login page or server error page.

Can formatting fix every parse error?

No. First confirm the input is actually JSON.

Related tools and guides

JSON JSON Validator and Formatter

Validate JSON, format it for reading, or minify it for compact API payloads without sending data to an external API.

 HTTP HTTP Headers Checker

Analyze pasted HTTP response headers for cache, redirects, security headers and content-type issues without making server-side requests.

 cURL cURL Command Builder

Build readable cURL commands for API requests with method, headers, JSON body and safe auth placeholders.

 cURL cURL API Debugging Workflow for Developers

cURL is the simplest way to separate API behavior from SDK, framework or frontend code. Build a minimal request first, then compare it with the failing implementation.

Last updated: May 18, 2026