diff --git a/example-config.yaml b/example-config.yaml
index f4bc3d6..c296f2b 100644
--- a/example-config.yaml
+++ b/example-config.yaml
@@ -22,6 +22,8 @@ server:
     # The IP and port to listen to.
     hostname: 0.0.0.0
     port: 29316
+    # Public base URL where the server is visible.
+    public_url: https://example.com
     # The base management API path.
     base_path: /_matrix/maubot/v1
     # The base path for the UI.
diff --git a/maubot/config.py b/maubot/config.py
index b1ee67f..57e6552 100644
--- a/maubot/config.py
+++ b/maubot/config.py
@@ -38,6 +38,7 @@ class Config(BaseFileConfig):
         copy("plugin_directories.db")
         copy("server.hostname")
         copy("server.port")
+        copy("server.public_url")
         copy("server.listen")
         copy("server.base_path")
         copy("server.ui_base_path")
diff --git a/maubot/instance.py b/maubot/instance.py
index 10db272..af7d86a 100644
--- a/maubot/instance.py
+++ b/maubot/instance.py
@@ -60,6 +60,7 @@ class PluginInstance:
     inst_db: sql.engine.Engine
     inst_db_tables: Dict[str, sql.Table]
     inst_webapp: web.Application
+    inst_webapp_url: str
     started: bool
 
     def __init__(self, db_instance: DBPlugin):
@@ -73,6 +74,7 @@ class PluginInstance:
         self.inst_db = None
         self.inst_db_tables = None
         self.inst_webapp = None
+        self.inst_webapp_url = None
         self.base_cfg = None
         self.cache[self.id] = self
 
@@ -113,7 +115,7 @@ class PluginInstance:
             db_path = os.path.join(self.mb_config["plugin_directories.db"], self.id)
             self.inst_db = sql.create_engine(f"sqlite:///{db_path}.db")
         if self.loader.meta.webapp:
-            self.inst_webapp = self.webserver.get_instance_subapp(self.id)
+            self.inst_webapp, self.inst_webapp_url = self.webserver.get_instance_subapp(self.id)
         self.log.debug("Plugin instance dependencies loaded")
         self.loader.references.add(self)
         self.client.references.add(self)
@@ -168,7 +170,8 @@ class PluginInstance:
             self.config = config_class(self.load_config, lambda: self.base_cfg, self.save_config)
         self.plugin = cls(client=self.client.client, loop=self.loop, http=self.client.http_client,
                           instance_id=self.id, log=self.log, config=self.config,
-                          database=self.inst_db, webapp=self.inst_webapp)
+                          database=self.inst_db, webapp=self.inst_webapp,
+                          webapp_url=self.inst_webapp_url)
         try:
             await self.plugin.start()
         except Exception:
diff --git a/maubot/plugin_base.py b/maubot/plugin_base.py
index 1e40bd9..ce2d2f4 100644
--- a/maubot/plugin_base.py
+++ b/maubot/plugin_base.py
@@ -37,7 +37,8 @@ class Plugin(ABC):
 
     def __init__(self, client: 'MaubotMatrixClient', loop: AbstractEventLoop, http: ClientSession,
                  instance_id: str, log: Logger, config: Optional['BaseProxyConfig'],
-                 database: Optional[Engine], webapp: Optional[Application]) -> None:
+                 database: Optional[Engine], webapp: Optional[Application],
+                 webapp_url: Optional[str]) -> None:
         self.client = client
         self.loop = loop
         self.http = http
@@ -46,6 +47,7 @@ class Plugin(ABC):
         self.config = config
         self.database = database
         self.webapp = webapp
+        self.webapp_url = webapp_url
         self._handlers_at_startup = []
 
     async def start(self) -> None:
diff --git a/maubot/server.py b/maubot/server.py
index ed3eebf..2bab5a7 100644
--- a/maubot/server.py
+++ b/maubot/server.py
@@ -13,6 +13,7 @@
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
+from typing import Tuple
 import logging
 import asyncio
 
@@ -49,14 +50,16 @@ class MaubotServer:
 
         self.runner = web.AppRunner(self.app, access_log_class=AccessLogger)
 
-    def get_instance_subapp(self, instance_id: str) -> web.Application:
+    def get_instance_subapp(self, instance_id: str) -> Tuple[web.Application, str]:
+        subpath = self.config["server.plugin_base_path"].format(id=instance_id)
+        url = self.config["server.public_url"] + subpath
         try:
-            return self.subapps[instance_id]
+            return self.subapps[instance_id], url
         except KeyError:
             app = web.Application(loop=self.loop)
-            self.app.add_subapp(self.config["server.plugin_base_path"].format(id=instance_id), app)
+            self.app.add_subapp(subpath, app)
             self.subapps[instance_id] = app
-            return app
+            return app, url
 
     def remove_instance_webapp(self, instance_id: str) -> None:
         try:
diff --git a/setup.py b/setup.py
index a25d1a8..b58bfca 100644
--- a/setup.py
+++ b/setup.py
@@ -21,7 +21,7 @@ setuptools.setup(
     packages=setuptools.find_packages(),
 
     install_requires=[
-        "mautrix>=0.4.dev20,<0.5",
+        "mautrix>=0.4.dev24,<0.5",
         "aiohttp>=3.0.1,<4",
         "SQLAlchemy>=1.2.3,<2",
         "alembic>=1.0.0,<2",