HTTP 4xx Client Error

Severity: Warning

What does this mean?

The server responded with an HTTP 4xx status code (other than 401, 403, or 404, which have their own issue types). 4xx errors indicate that the request was rejected by the server due to a client-side issue. Common examples include 400 (Bad Request), 405 (Method Not Allowed), and 429 (Too Many Requests).

Why this is a problem

A 4xx error on a basic HTTP request to a domain suggests the server is not configured to handle standard web traffic. This could indicate a misconfigured server, an API endpoint that is not meant to serve web pages, or access restrictions that are blocking the request.

What you should do

• Check the specific HTTP status code to understand the error
• Verify the server is configured to handle requests for this domain
• If the endpoint is an API, this may be expected behavior — consider whether the DNS record is appropriate
• If the server is misconfigured, review the web server or application configuration