# Collabora Online host determination problem? **URL:** \ **Category:** Installation & Configuration\ **Created:** [April 4, 2025, 10:51am UTC](https://forum.collaboraonline.com/t/collabora-online-host-determination-problem/3572 "2025-04-04T10:51:51Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![wweiers](https://avatars.discourse-cdn.com/v4/letter/w/c0e974/32.png) [@wweiers](https://forum.collaboraonline.com/u/wweiers)\ **Post date:** [April 4, 2025, 10:51am UTC](https://forum.collaboraonline.com/t/collabora-online-host-determination-problem/3572/1 "2025-04-04T10:51:51Z")
Hello, I currently have an instance of LibreOffice Online (LOOL) running in a Docker container, providing services to multiple clients. Thanks to an Apache reverse proxy, client A can edit their documents at https://clientA.domain.com, client B at https://clientB.domain.com, and so on. Everything is working perfectly. I have started testing, in the same environment, to **migrate to Collabora Online (COOL)**. I am replicating the same conditions: a Docker container behind the same Apache reverse proxy, whose configuration has been adapted to the new paths (as indicated in the COOL documentation). I do not specify any **server\_name** parameter when launching the COOL container because I want it to be **dynamically determined** for each request, similar to what my LOOL container currently does very well. Unfortunately, this new deployment with COOL does not work: COOL cannot or does not know how to determine the caller’s hostname using the **host** or the **X-Forwarded-Host** header of the incoming HTTP request. It systematically uses the hostname assigned to the container by Docker! If I specify the server\_name “clientA.domain.com” when creating the COOL container, client A can edit their documents without any issues (which proves that the rest of the configuration is OK)… but not client B, nor client C, nor… Is there a limitation in COOL that only allows deployment behind a single host (no dynamic host determination) ? Thank you in advance for your response. > Env : Collabora Online 24.04.13.3 - SSL Termination (ssl.enable=false and ssl.termination=true] ---
**Author:** ![darshan](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.collaboraonline.com/darshan/32/2230_2.png) [@darshan](https://forum.collaboraonline.com/u/darshan)\ **Post date:** [April 8, 2025, 6:53am UTC](https://forum.collaboraonline.com/t/collabora-online-host-determination-problem/3572/2 "2025-04-08T06:53:06Z")
hii @wweiers Welcome to collabora online forum Yes, by default **COOL (Collabora Online)** is **not configured to dynamically accept any host** via `Host` or `X-Forwarded-Host` headers like LOOL did. However, you **can** support multiple dynamic virtual hosts using the `alias_group` mechanism and some configuration in `coolwsd.xml`. Unlike LOOL, **COOL introduced stricter hostname validation** to improve security. That means it validates requests against `server_name` and **does not** automatically trust `Host` or `X-Forwarded-Host`. COOL, by default, only serves the hostname passed in `--o:server_name`. If not set, it uses the system hostname — hence your observation that all requests route to the container’s hostname ---
**Author:** ![darshan](https://dub1.discourse-cdn.com/flex013/user_avatar/forum.collaboraonline.com/darshan/32/2230_2.png) [@darshan](https://forum.collaboraonline.com/u/darshan)\ **Post date:** [April 11, 2025, 5:37am UTC](https://forum.collaboraonline.com/t/collabora-online-host-determination-problem/3572/3 "2025-04-11T05:37:42Z")
Closed on April 11, 2025, 5:37am UTC