Thanks for the PR @user121216 👍 This issue is likely experienced by many users and would be a welcome solution!

Feedback:

• Could you check in Some URLs not resolved appropriately behind proxy #6644 whether this is directly related and the same issue? EDIT: also for Apache in https proxy call brakes logo.svg URL (also some strange redirect removing /piwik/ folder) and getting a "No input file specified." response. #11765

• we would like to update the Proxy FAQ to explain this setting, here is a first proposal (if you have any feedback?):

If you're using Piwik behind a reverse proxy with a different path such as rewrite ^/piwik/(.*)$ /$1 break; (in nginx.conf), you would need to:

1. configure the web server to provide a header: proxy_set_header X-Forwarded-Uri /piwik;.
2. in Piwik config/config.ini.php, add proxy_uri_header = 1 below the [General] section, so that Piwik will use the X-Forwarded-Uri header.

I wonder if using an HTTP header is a better choice than allowing for a uri_prefix variable directly in the global.php.ini. If there is no case where we want to dynamically change the URI prefix, then we do not need to send it with every request to Piwik. I don't know all of the ways in which Piwik is used though, so maybe that's a feature?

@user121216 what influenced your decision to use an HTTP header?

@ToBeReplaced My decision was inspired by the proxy_host_headers variable and the docker environment. I have 2 docker containers (Nginx proxy and Apache with Piwik). The Piwik container is a standalone solution and the rewrite rule is from the Nginx proxy, so I wanted to keep the reason and the config together in one file (nginx.conf). Another solution could be also to run the Piwik instance under the right directory on the Apache container (/piwik), but this is not a smart way for me.

@mattab You're right. These issues are similar. Next time I have to search better :)

@user121216 Thanks for the explanation, and thanks for submitting the PR. Consistency with the way piwik handles other proxy details seems worthwhile. Looks good to me.

Thanks for this PR, @user121216! I'd love to see this merged as I'm running into this problem with the official Docker container.

Thanks for the PR @user121216 and to the others for the feedback. I've updated FAQ @ https://piwik.org/faq/how-to-install/faq_98/

@user121216 @fefrei @ToBeReplaced if you're using our official Docker Piwik image, could you please check / confirm if the Docker config is currently correct in terms of configuring proxy_set_header X-Forwarded-Uri /piwik; ? it would be great to clarify it in the README of the project, or maybe in the code something can be done (haven't checked). Thanks

and if you have any feedback about the FAQ please let me know, i'm not 100% sure it is all correct or clear

It looks like https://hub.docker.com/r/_/piwik/ hasn't been updated yet, so I cannot test this in the moment.