Bing reports HTTP 400–499 errors on my website
Bing Webmaster Tools sometimes reports “HTTP 400–499 errors” even when your website loads normally in a browser and Google shows no major issues. In most cases, this is not a penalty. It usually means Bing could not complete a scan or fetch reliably because a security or bot protection layer interfered with how Bing requested the pages.
This guide explains what it means, what to check, and how to verify improvements using simple PowerShell tests.
What Bing means by HTTP 400–499 errors
HTTP 400–499 status codes are client side response codes such as 403 Forbidden or 404 Not Found.
However, in Bing reports, this message can also appear when Bing experiences an access issue that looks like a client side failure, even if the page works for normal visitors. This can include security challenges, blocked scans, or inconsistent responses during scanning.
Before changing anything, confirm what is actually happening
If your site uses Cloudflare, Wordfence, or another security layer, the first step is to confirm whether Bingbot can fetch pages cleanly and consistently.
What a healthy result looks like
HTTP status code 200
Content type text slash html
In the PowerShell output you will see something like:
text/html; charset=UTF-8
No security or challenge page returned
Bing Site Scan completes without errors
Cloudflare checks that commonly affect Bing scans
If you use Cloudflare, review the following areas carefully.
Security rules and bot handling
If you have created a rule to handle Bingbot, ensure it runs before other security rules.
If your Cloudflare plan does not provide an Allow action, Skip is acceptable.
Suggested matching logic
User Agent contains bingbot
OR User Agent contains msnbot
Suggested skip settings
Managed rules
Rate limiting rules
Super Bot Fight Mode rules, if enabled
Other custom security rules, where appropriate
Note
Skip rules do not bypass IP Access Rules. Country restrictions or allow lists at account or zone level can still block Bing and must be reviewed separately.
Browser Integrity Check. Test it on and off
Browser Integrity Check can interfere with non browser clients, including some crawlers and scan tools.
Google may tolerate this behaviour. Bing often does not.
How to test safely
Note whether Browser Integrity Check is currently enabled
Run the PowerShell tests below and save the results
Turn Browser Integrity Check off
Purge Cloudflare cache once
Run the PowerShell tests again
Compare the results
If there is no difference, turn it back on
If behaviour improves, keep it off and rely on other protections
Where to find it in Cloudflare
Security
Settings
Browser Integrity Check
Purge cache once after rule changes
If Cloudflare is serving cached HTML, Bingbot may continue receiving an older response even after security changes.
A single cache purge helps ensure Bing receives a clean response.
Cloudflare steps
Caching
Purge cache
Purge everything
Do not purge repeatedly. One purge after changes is normally sufficient.
PowerShell tests to confirm Bingbot access
These tests simulate Bingbot and confirm Cloudflare is returning clean HTML.
Test 1. Confirm headers and status
PowerShell code block
$ua = “Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)”
$r = Invoke-WebRequest -Uri “https://itsupportforsmallbusinessesinlondon.net/” -Headers @{ “User-Agent” = $ua } -Method Head
$r.StatusCode
$r.Headers[“Content-Type”]
$r.Headers[“Server”]
$r.Headers[“CF-Cache-Status”]
$r.Headers[“cf-ray”]
How to interpret the results
StatusCode should be 200
Content Type should be text slash html
Server may show cloudflare
Cache status may show HIT or MISS
Example of a good outcome
200
text/html; charset=UTF-8
cloudflare
Test 2. Check for challenge pages
PowerShell code block
$ua = “Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)”
$html = Invoke-WebRequest -Uri “https://itsupportforsmallbusinessesinlondon.net/” -Headers @{ “User-Agent” = $ua }
$html.StatusCode
($html.Content | Select-String -Pattern “cf-chl|challenge|captcha|Attention Required|Cloudflare” -AllMatches).Matches.Value
How to interpret the results
StatusCode should be 200
No matches should be returned
Test 3. Confirm cache refresh after purge
Run this test twice after purging cache.
PowerShell code block
$ua = “Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)”
$r = Invoke-WebRequest -Uri “https://itsupportforsmallbusinessesinlondon.net/” -Headers @{ “User-Agent” = $ua } -Method Head
$r.StatusCode
$r.Headers[“Content-Type”]
$r.Headers[“Server”]
$r.Headers[“CF-Cache-Status”]
$r.Headers[“cf-ray”]
Expected outcome
First run. MISS
Second run. HIT
After verification, rerun Bing Site Scan
Once the tests show clean results, rerun Bing Site Scan and request indexing for priority pages.
Cloudflare reference
Cloudflare official guidance on blocked Bing site scans.
When to get help
If Bingbot receives HTTP 200 and clean HTML but Bing still reports HTTP 400–499 errors after scanning, the cause is often an IP access rule, a strict security posture outside WAF rules, or an intermittent Bing scan issue.
In those cases, a methodical review is usually more effective than repeated changes.
If you want a second opinion, we can review Cloudflare security settings, caching behaviour, and Bingbot access, and explain the safest next steps.