diff --git a/Cytoplasm b/Cytoplasm
index 9108fef..346b912 160000
--- a/Cytoplasm
+++ b/Cytoplasm
@@ -1 +1 @@
-Subproject commit 9108fef7018010e6b49a111856ca0553333804f8
+Subproject commit 346b912a0633cceac10780b8a103f6c89b5ba89f
diff --git a/src/Room.c b/src/Room.c
index 20d262c..a4a5b97 100644
--- a/src/Room.c
+++ b/src/Room.c
@@ -2054,6 +2054,144 @@ RoomContainsUser(Room *room, char *user)
 
     return ret;
 }
+bool
+RoomCanJoin(Room *room, char *user)
+{
+    HashMap *state;
+    HashMap *joinRule = NULL;
+    char *joinRuleV;
+    bool ret;
+    if (!room || !user)
+    {
+        return false;
+    }
+
+    state = StateCurrent(room);
+
+    /* No rooms for banned people! */
+    if (RoomUserHasMembership(room, state, user, "ban"))
+    {
+        ret = false;
+        goto end;
+    }
+
+    /* Check join_rules */
+    joinRule = RoomEventFetch(
+        room,
+        StateGet(state, "m.room.join_rules", "")
+    );
+    joinRuleV = JsonValueAsString(HashMapGet(joinRule, "join_rule"));
+
+    if (StrEquals(joinRuleV, "public"))
+    {
+        /* Anyone can join the room without any prior action. */
+        ret = true;
+        goto end;
+    }
+    if (StrEquals(joinRuleV, "invite"))
+    {
+        /* A user must first receive an invite from someone already in the 
+         * room in order to join. */
+        ret = RoomUserHasMembership(room, state, user, "invite");
+        goto end;
+    }
+
+    if (StrEquals(joinRuleV, "knock"))
+    {
+        /* TODO: Knocking and restricted rooms. */
+        ret = false;
+        goto end;
+    }
+    if (StrEquals(joinRuleV, "restricted"))
+    {
+        /* TODO: Knocking and restricted rooms. */
+        ret = false;
+        goto end;
+    }
+    if (StrEquals(joinRuleV, "knock_restricted"))
+    {
+        /* TODO: Knocking and restricted rooms. */
+        ret = false;
+        goto end;
+    }
+
+    /* All other rooms are considered private. */
+    ret = false;
+end:
+    StateFree(state);
+    JsonFree(joinRule);
+    return ret;
+}
+
+static char *
+GetServerName(Db * db)
+{
+    char *name;
+
+    Config config;
+
+    ConfigLock(db, &config);
+    if (!config.ok)
+    {
+        return NULL;
+    }
+
+    name = StrDuplicate(config.serverName);
+
+    ConfigUnlock(&config);
+
+    return name;
+}
+bool
+RoomJoin(Room *room, User *user)
+{
+    CommonID *userId    = NULL;
+    char *userString    = NULL;
+    char *server        = NULL;
+    HashMap *content    = NULL;
+    HashMap *event      = NULL;
+    HashMap *pdu        = NULL;
+    bool ret            = false;
+
+    if (!room || !user)
+    {
+        return false;
+    }
+
+    server = GetServerName(room->db);
+    if (!server)
+    {
+        return false;
+    }
+    userId = UserIdParse(UserGetName(user), server);
+    userId->sigil = '@';
+    userString = ParserRecomposeCommonID(*userId);
+    Free(server);
+    server = NULL;
+
+    if (!RoomCanJoin(room, userString))
+    {
+        ret = false;
+        goto end;
+    }
+
+    content = HashMapCreate();
+    JsonSet(content, JsonValueString("join"), 1, "membership");
+    event = RoomEventCreate(userString, "m.room.member", userString, content);
+    pdu = RoomEventSend(room, event);
+
+    ret = !!pdu;
+    /* TODO: Note down *somewhere* that the user joined. */
+end:
+    UserIdFree(userId);
+    JsonFree(event);
+    JsonFree(pdu);
+    if (userString)
+    {
+        Free(userString);
+    }
+    return ret;
+}
 HashMap *
 RoomEventClientify(HashMap *pdu)
 {
diff --git a/src/Routes.c b/src/Routes.c
index a55c19c..c5d58dd 100644
--- a/src/Routes.c
+++ b/src/Routes.c
@@ -76,6 +76,10 @@ RouterBuild(void)
     R("/_matrix/client/v3/user/(.*)/filter", RouteFilter);
     R("/_matrix/client/v3/user/(.*)/filter/(.*)", RouteFilter);
 
+    R("/_matrix/client/v3/rooms/(.*)/send/(.*)/(.*)", RouteSendEvent);
+    R("/_matrix/client/v3/rooms/(.*)/event/(.*)", RouteFetchEvent);
+    R("/_matrix/client/v3/rooms/(.*)/join", RouteJoinRoom);
+
     R("/_matrix/client/v3/createRoom", RouteCreateRoom);
 
     R("/_matrix/client/v3/directory/room/(.*)", RouteAliasDirectory);
@@ -91,65 +95,6 @@ RouterBuild(void)
     R("/_telodendria/admin/v1/tokens/(.*)", RouteAdminTokens);
     R("/_telodendria/admin/v1/tokens", RouteAdminTokens);
 
-    R("/_matrix/client/r0/capabilities", RouteCapabilities);
-    R("/_matrix/client/r0/login", RouteLogin);
-    R("/_matrix/client/r0/logout", RouteLogout);
-    R("/_matrix/client/r0/logout/(all)", RouteLogout);
-    R("/_matrix/client/r0/register", RouteRegister);
-    R("/_matrix/client/r0/register/(available)", RouteRegister);
-    R("/_matrix/client/r0/refresh", RouteRefresh);
-
-    R("/_matrix/client/r0/account/whoami", RouteWhoami);
-    R("/_matrix/client/r0/account/password", RouteChangePwd);
-    R("/_matrix/client/r0/account/deactivate", RouteDeactivate);
-
-    R("/_matrix/client/v1/register/m.login.registration_token/validity", RouteTokenValid);
-
-    R("/_matrix/client/r0/account/password/(email|msisdn)/requestToken", RouteRequestToken);
-    R("/_matrix/client/r0/register/(email|msisdn)/requestToken", RouteRequestToken);
-
-    R("/_matrix/client/r0/profile/(.*)", RouteUserProfile);
-    R("/_matrix/client/r0/profile/(.*)/(avatar_url|displayname)", RouteUserProfile);
-
-    R("/_matrix/client/r0/user/(.*)/filter", RouteFilter);
-    R("/_matrix/client/r0/user/(.*)/filter/(.*)", RouteFilter);
-
-    R("/_matrix/client/r0/createRoom", RouteCreateRoom);
-
-    R("/_matrix/client/r0/directory/room/(.*)", RouteAliasDirectory);
-    R("/_matrix/client/r0/rooms/(.*)/aliases", RouteRoomAliases);
-
-
-    R("/_matrix/client/v3/capabilities", RouteCapabilities);
-    R("/_matrix/client/v3/login", RouteLogin);
-    R("/_matrix/client/v3/logout", RouteLogout);
-    R("/_matrix/client/v3/logout/(all)", RouteLogout);
-    R("/_matrix/client/v3/register", RouteRegister);
-    R("/_matrix/client/v3/register/(available)", RouteRegister);
-    R("/_matrix/client/v3/refresh", RouteRefresh);
-
-    R("/_matrix/client/v3/account/whoami", RouteWhoami);
-    R("/_matrix/client/v3/account/password", RouteChangePwd);
-    R("/_matrix/client/v3/account/deactivate", RouteDeactivate);
-
-    R("/_matrix/client/v1/register/m.login.registration_token/validity", RouteTokenValid);
-
-    R("/_matrix/client/v3/account/password/(email|msisdn)/requestToken", RouteRequestToken);
-    R("/_matrix/client/v3/register/(email|msisdn)/requestToken", RouteRequestToken);
-
-    R("/_matrix/client/v3/profile/(.*)", RouteUserProfile);
-    R("/_matrix/client/v3/profile/(.*)/(avatar_url|displayname)", RouteUserProfile);
-
-    R("/_matrix/client/v3/user/(.*)/filter", RouteFilter);
-    R("/_matrix/client/v3/user/(.*)/filter/(.*)", RouteFilter);
-
-    R("/_matrix/client/v3/rooms/(.*)/send/(.*)/(.*)", RouteSendEvent);
-    R("/_matrix/client/v3/rooms/(.*)/event/(.*)", RouteFetchEvent);
-    R("/_matrix/client/v3/createRoom", RouteCreateRoom);
-
-    R("/_matrix/client/v3/directory/room/(.*)", RouteAliasDirectory);
-    R("/_matrix/client/v3/rooms/(.*)/aliases", RouteRoomAliases);
-
 #undef R
 
     return router;
diff --git a/src/Routes/RouteJoinRoom.c b/src/Routes/RouteJoinRoom.c
new file mode 100644
index 0000000..a0b324f
--- /dev/null
+++ b/src/Routes/RouteJoinRoom.c
@@ -0,0 +1,165 @@
+/*
+ * Copyright (C) 2022-2024 Jordan Bancino <@jordan:bancino.net> with
+ * other valuable contributors. See CONTRIBUTORS.txt for the full list.
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#include <Routes.h>
+
+
+#include <Cytoplasm/HashMap.h>
+#include <Cytoplasm/Memory.h>
+#include <Cytoplasm/Json.h>
+#include <Cytoplasm/Str.h>
+
+#include <User.h>
+#include <Room.h>
+#include <string.h>
+
+#include <Schema/Filter.h>
+
+static char *
+GetServerName(Db * db)
+{
+    char *name;
+
+    Config config;
+
+    ConfigLock(db, &config);
+    if (!config.ok)
+    {
+        return NULL;
+    }
+
+    name = StrDuplicate(config.serverName);
+
+    ConfigUnlock(&config);
+
+    return name;
+}
+
+ROUTE_IMPL(RouteJoinRoom, path, argp)
+{
+    RouteArgs *args = argp;
+    Db *db = args->matrixArgs->db;
+
+    HashMap *request = NULL;
+    HashMap *response = NULL;
+
+    User *user = NULL;
+    char *token = NULL;
+    CommonID *id = NULL;
+
+    char *roomId = ArrayGet(path, 0);
+    char *sender = NULL, *serverName = NULL;
+
+    Room *room = NULL;
+
+    char *err;
+
+    if (!roomId)
+    {
+        /* Should be impossible */
+        HttpResponseStatus(args->context, HTTP_INTERNAL_SERVER_ERROR);
+        return MatrixErrorCreate(M_UNKNOWN, NULL);
+    }
+    if (HttpRequestMethodGet(args->context) != HTTP_POST)
+    {
+        err = "Unknown request method.";
+        HttpResponseStatus(args->context, HTTP_BAD_REQUEST);
+        response = MatrixErrorCreate(M_UNRECOGNIZED, err);
+        goto finish;
+    }
+
+    request = JsonDecode(HttpServerStream(args->context));
+    if (!request)
+    {
+        HttpResponseStatus(args->context, HTTP_BAD_REQUEST);
+        response = MatrixErrorCreate(M_NOT_JSON, NULL);
+        goto finish;
+    }
+
+    serverName = GetServerName(db);
+    if (!serverName)
+    {
+        HttpResponseStatus(args->context, HTTP_INTERNAL_SERVER_ERROR);
+        response = MatrixErrorCreate(M_UNKNOWN, NULL);
+        goto finish;
+    }
+
+    response = MatrixGetAccessToken(args->context, &token);
+    if (response)
+    {
+        goto finish;
+    }
+
+    user = UserAuthenticate(db, token);
+    if (!user)
+    {
+        HttpResponseStatus(args->context, HTTP_UNAUTHORIZED);
+        response = MatrixErrorCreate(M_UNKNOWN_TOKEN, NULL);
+        goto finish;
+    }
+    id = UserIdParse(UserGetName(user), serverName);
+    id->sigil = '@';
+    sender = ParserRecomposeCommonID(*id);
+    
+    room = RoomLock(db, roomId);
+    if (RoomContainsUser(room, sender))
+    {
+        err = "User is already in the room.";
+        HttpResponseStatus(args->context, HTTP_UNAUTHORIZED);
+        response = MatrixErrorCreate(M_FORBIDDEN, err);
+        goto finish;
+    }
+    if (!RoomCanJoin(room, sender))
+    {
+        err = "User cannot be in the room.";
+        HttpResponseStatus(args->context, HTTP_UNAUTHORIZED);
+        response = MatrixErrorCreate(M_FORBIDDEN, err);
+        goto finish;
+    }
+    /* TODO: Custom reason parameter. */
+    if (!RoomJoin(room, user))
+    {
+        err = "User could not be the room due to unknown reasons.";
+        HttpResponseStatus(args->context, HTTP_INTERNAL_SERVER_ERROR);
+        response = MatrixErrorCreate(M_UNKNOWN, err);
+        goto finish;
+    }
+
+    response = HashMapCreate();
+    JsonSet(response, JsonValueString(roomId), 1, "room_id");
+
+finish:
+    UserIdFree(id);
+    if (sender)
+    {
+        Free(sender);
+    }
+    if (serverName)
+    {
+        Free(serverName);
+    }
+    RoomUnlock(room);
+    UserUnlock(user);
+    return response;
+}
diff --git a/src/include/Room.h b/src/include/Room.h
index 95e8f81..ec66fc4 100644
--- a/src/include/Room.h
+++ b/src/include/Room.h
@@ -217,6 +217,18 @@ extern void RoomFreeReverse(Array *);
  */
 extern bool RoomContainsUser(Room *, char *);
 
+/**
+ * Checks whenever an user can join a specific room, 
+ * given it's permissions.
+ */
+extern bool RoomCanJoin(Room *, char *);
+
+/**
+ * Makes a local user join a room, and returns true if 
+ * the room was joined.
+ */
+extern bool RoomJoin(Room *, User *);
+
 /**
  * Adds or overwrites a room alias.
  */
diff --git a/src/include/Routes.h b/src/include/Routes.h
index e0c328e..0c90b69 100644
--- a/src/include/Routes.h
+++ b/src/include/Routes.h
@@ -100,8 +100,9 @@ ROUTE(RouteConfig);
 ROUTE(RoutePrivileges);
 
 ROUTE(RouteCreateRoom);
-ROUTE(RouteSendEvent);
 ROUTE(RouteFetchEvent);
+ROUTE(RouteSendEvent);
+ROUTE(RouteJoinRoom);
 
 ROUTE(RouteAliasDirectory);
 ROUTE(RouteRoomAliases);