Troubleshooting of HTTP errors

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HTTP status code

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Troubleshooting HTTP Status Errors

400 Bad Request

Root cause: The request itself is malformed. According to the spec, this means "the server cannot or will not process the request due to something perceived to be a client error" — such as invalid syntax, incorrect request message framing, or deceptive request routing.

Possible fix:

• Review and correct the request headers

403 Forbidden

See: How to fix the 403 forbidden error

404 Not Found

Fix: Verify that the URL is correct. For more details, see 404 Not Found, possible solutions for pages not found".

405 Method Not Allowed

Fix: Confirm that the target resource supports the HTTP method you're using. For example, the endpoint may only accept POST requests while you're sending a GET request.

414 Request-URI Too Large

Fix: Switch from GET to POST so the data is sent in the request body instead of the URL.

415 Unsupported Media Type

Fix: Explicitly declare the correct Content-Type or Content-Encoding in the request, or access the data directly. For instance, when calling a RESTful API, this error can often be resolved by adding the following header:

Content-Type: application/json

429 Too Many Requests

Root cause:

• The client is hitting the website or API more frequently than the service allows.

Fixes:

• Throttle your requests: Add or increase a delay between requests based on your usage pattern and the service's limits (e.g., pause 1 second between calls).
• Check the API rate limits: Consult the provider's documentation for limits such as Requests Per Minute (RPM) or Requests Per Day (RPD), and find out whether you can request a higher quota.
• Use exponential backoff: Detect HTTP 429 responses in your

 application, then retry with progressively longer delays (e.g., 2s → 4s → 8s) until the request succeeds or a maximum retry count is reached.

502 Bad Gateway

Cause:

• A failure between upstream network devices/servers — not something the end user can fix directly.

Fixes:

• Hard-refresh the page to bypass the browser cache
• Wait a moment and try again

Error 1020: Access Denied

• See the linked guide on resolving Error 1020 (Access Denied) to restore access to your website.

HTTP Cats or Dogs

From HTTP Cats

Related websites:

• HTTP Status Dogs

Other possible root causes

• CDN (Content delivery network)

Mock HTTP status error page tools

The testing sites that can return 500 and various other HTTP status codes on demand

• The Internet
• httpstatus.io: A bulk checker for HTTP status codes, headers, and redirects, which also offers mock endpoints, e.g. 500
• Postman Echo: A request/response testing service with status code endpoints, e.g. 500

Related pages

• Troubleshooting of curl errors
• Test connectivity for the web service

References

Troubleshooting of ...

• Troubleshooting of Excel errors

• PHP, cUrl, Python, selenium, HTTP status code errors

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• HTML/Javascript: Troubleshooting of javascript, XPath

• Software: Mediawiki, Docker, FTP problems, online conference software

• Test connectivity for the web service, Web Ping, Network problem, Web user behavior, Web scrape troubleshooting

Template

• Bug report template