diff --git a/docker-compose.yml b/docker-compose.yml
index 52ab863..def10dc 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -43,15 +43,15 @@ services:
     ports:
       # HTTP
       - target: 80
-        published: 80
+        published: ${HTTP_PORT:-80}
         protocol: tcp
       # HTTPS
       - target: 443
-        published: 443
+        published: ${HTTPS_PORT:-443}
         protocol: tcp
       # HTTP/3
       - target: 443
-        published: 443
+        published: ${HTTP3_PORT:-443}
         protocol: udp
 
 # Mercure is installed as a Caddy module, prevent the Flex recipe from installing another service
diff --git a/docs/build.md b/docs/build.md
index 71a88fa..744b89c 100644
--- a/docs/build.md
+++ b/docs/build.md
@@ -31,3 +31,11 @@ Use the `SERVER_NAME` environment variable to define your custom server name(s).
     SERVER_NAME="symfony.wip, caddy:80" docker-compose up --build
 
 If you use Mercure, keep `caddy:80` in the list to allow the PHP container to request the caddy service.
+
+## Using custom HTTP ports
+
+Use the environment variables `HTTP_PORT`, `HTTPS_PORT` and/or `HTTP3_PORT` to adjust the ports to your needs, e.g.
+
+    HTTP_PORT=8000 HTTPS_PORT=4443 HTTP3_PORT=4443 docker-compose up --build
+
+to access your appplication on [https://localhost:4443](https://localhost:4443).