Unexpected 406 error when scanning https://monitor.mozilla.org/

[edwinmh]

What information was incorrect, unhelpful, or incomplete?

I'm using the @mdn/mdn-http-observatory package as part of my own report automation engine.

When attempting to scan the domain https://monitor.mozilla.org/, I consistently receive the following response:

Error: Site did respond with an unexpected HTTP status code 406.

The same behavior occurs on the official Observatory web interface at https://observatory.mozilla.org.

I assume this may be due to strict content negotiation settings, headers, or a block on the scanner’s User-Agent — but it’s surprising that a Mozilla-managed domain fails to be scanned by its own scanning tool.

Because of this issue, I’m unable to generate a valid HTTP Observatory report for that domain within WebPerformance Report, a tool I’ve built to help developers receive weekly performance and security reports.

What did you expect to see?

I expected the domain https://monitor.mozilla.org/ to be scanned normally using @mdn/mdn-http-observatory, returning a grade and analysis as it does for other public sites.

Do you have any supporting links, references, or citations?

No response

Do you have anything more you want to share?

I just want to thank you for building and maintaining HTTP Observatory.
It's an incredibly valuable tool for promoting better web security, and it's great to see it open to the community. 🙌

[mdn-bot]

Thanks for reporting, @edwinmh.

I have shared this issue with the colleagues from the Monitor team, and this might be a firewall rule that's blocking the scan. Given that we don't have similar reports for other sites, this is not a priority for us (the MDN team) to investigate.

However, should you find a way to make the scan work, please don't hesitate to share this with us.