A permissive robots.txt is not enough if the CDN or firewall returns a challenge, error, or empty page to the crawlers. Compare the response actually received with the one expected, then correct the precise rule that blocks access to public resources.
Observe a representative URL
Choose an important page, its image and the robots.txt file. Note HTTP status, redirects, content type, and body returned. A 200 status can hide a verification page instead of the item. Record the date and query identifier provided by the infrastructure, if available. A browser connected to the administration is not a sufficient test of public access.
Read the full answer, not just its status
Diagnosis should distinguish the request, the response and its content. An HTTP success does not prove that the article was served. Conversely, an error found once is not enough to characterize a permanent blockage. Compare the same URLs to documented times, and then search for the relevant queries in the infrastructure logs.
| observed response | Hypothesis to verify | Next check |
|---|---|---|
| 200 with the expected text | Public access available for this request | Also check images, links and metadata |
| 200 with a navigation challenge | Protection served instead of content | View the associated event in the CDN |
| 403 | Access denied according to a rule or authorization | Identify the layer that made the decision |
| 429 | Flow limitation or other frequency rule | Read headers and applied policy |
| Successive redirects | URL route or configuration to review | Examine the final destination and domain variants |
Since Windows with curl.exe, the commands below allow you to keep the headers and the body of the response, then identify the final destination. Replace the address with a public page that you are allowed to control. The domain is illustrative; These lines prove no results on your hosting. With another system, in particular, adapt the name of the executable and the ignored output file.
curl.exe -sS -D headers.txt -o page.html https://example.com/guide/
curl.exe -sS -L -o NUL -w "%{http_code} %{url_effective}\n" https://example.com/guide/Compare the logs
An upstream blocked request may never reach the original server. Check the CDN and server events on the same time window. Look for protection rules, flow limits, and geographic restrictions. Do not copy sensitive settings publicly. The goal is to isolate a rule that explains the gap between the expected response and the observed response.
Verify identity before an exception
A robot name in the user-agent can be imitated. For Google, use the methods published by the operator: DNS verification or official address ranges, depending on your device. For another robot, check out its documentation. A local simulation of the user-agent helps test a response; It does not prove that the real robot encounters exactly the same treatment.
Fictitious example: an inaccessible image
The HTML of a guide is accessible, but its illustration receives a challenge because an image path falls under an overly broad protection rule. The team changes only the rule affecting those public resources, then checks the responses and server load. The test covers ordinary visitors and verified crawler access, while keeping administration areas and sensitive functions protected.
Construct a limited exception and check its effect
Start with a test rule for the public resource concerned. Record the behaviour before and after, the verified crawler identity when relevant, and the test duration. A global firewall change would make that comparison harder. Check ordinary visitors too: an exception should preserve their journey and serve the same substantive content.
- Correlate events with a specific query identifier or time window. If the original server has not received anything, start with the upstream layer.
- Distinguish between the robots.txt policy, access control and speed protection. These mechanisms answer different questions; Modifying one does not automatically correct others.
- Replay the observations on the page, the main image and a neighboring URL. Also check the result after expiring or invalidating the cache according to your infrastructure method.
- Keep the backtracking procedure and the follow-up manager. Fault closing corresponds to a correct response reproduced, not to the disappearance of an isolated warning.
The Official Google Query Verification Helps to identify authentic access. A header simulation is not enough for this step. To avoid mixing identity and access, continue with the Control of the identity of crawlers in logs.
Document the correction
Keep Initial Rule, Change, Resource and Backtrack Method. Then watch for errors rather than lowering all protections. In search tools, inspect representative pages and allow time for processing. This control completes the Technical preparation of the site : It does not guarantee indexing or a citation. Also check that the images remain available after the cache expires.