diff --git a/rebar.config b/rebar.config
index b095f855..aea31198 100644
--- a/rebar.config
+++ b/rebar.config
@@ -65,9 +65,3 @@
           {source_url, "https://github.com/emqx/quic"}
          ]}.
 
-{dialyzer, [
-    {warnings, [unmatched_returns, error_handling]},
-    {plt_apps, all_apps},
-    {statistics, true}
-   ]
-}.
diff --git a/src/quicer.erl b/src/quicer.erl
index 662eb876..f28aefef 100644
--- a/src/quicer.erl
+++ b/src/quicer.erl
@@ -133,14 +133,13 @@
 %% export types
 -export_type([listener_handle/0,
               listener_opts/0,
+              listen_on/0,
               connection_handle/0,
               conn_opts/0,
               stream_handle/0,
               stream_opts/0
              ]).
 
-
-
 -type connection_opts() :: proplists:proplist() | conn_opts().
 -type listener_opts() :: proplists:proplist() | listen_opts().
 
@@ -173,32 +172,32 @@ close_lib() ->
 
 
 %% @doc Create a new registration.
--spec new_registration(Name, Profile) ->
-        quicer_nif:new_registration(Name, Profile).
+-spec new_registration(_Name, _Profile) ->
+        quicer_nif:new_registration().
 new_registration(Name, Profile) ->
   quicer_nif:new_registration(Name, Profile).
 
 %% @doc Shutdown a registration.
--spec shutdown_registration(Handle) ->
-        quicer_nif:shutdown_registration(Handle).
+-spec shutdown_registration(_Handle) ->
+        quicer_nif:shutdown_registration().
 shutdown_registration(Handle) ->
   quicer_nif:shutdown_registration(Handle).
 
 %% @doc Shutdown a registration with error code and silent flag.
--spec shutdown_registration(Handle, IsSilent, ErrCode) ->
-        quicer_nif:shutdown_registration(Handle, IsSilent, ErrCode).
+-spec shutdown_registration(reg_handle(), boolean(), uint64()) ->
+        quicer_nif:shutdown_registration().
 shutdown_registration(Handle, IsSilent, ErrCode) ->
   quicer_nif:shutdown_registration(Handle, IsSilent, ErrCode).
 
 %% @doc close a registration.
--spec close_registration(Handle) ->
-        quicer_nif:close_registration(Handle).
+-spec close_registration(reg_handle()) ->
+        quicer_nif:close_registration().
 close_registration(Handle) ->
   quicer_nif:close_registration(Handle).
 
 %% @doc get registration name
--spec get_registration_name(Handle) ->
-        quicer_nif:get_registration_name(Handle).
+-spec get_registration_name(reg_handle()) ->
+        quicer_nif:get_registration_name().
 get_registration_name(Handle) ->
   quicer_nif:get_registration_name(Handle).
 
@@ -958,7 +957,7 @@ peername(Handle) ->
 %% @doc Peer Cert in DER-encoded binary
 %% mimic {@link ssl:peername/1}
 -spec peercert(connection_handle() | stream_handle()) ->
-        {ok, Cert:: public_key:der_encoded()} | {error, any()}.
+        {ok, CertDerEncoded :: binary()} | {error, any()}.
 peercert(Handle) ->
   quicer_nif:peercert(Handle).
 
@@ -983,7 +982,7 @@ open_connection() ->
 
 %% @doc list all listeners
 -spec listeners() -> [{{ quicer_listener:listener_name()
-                       , quicer_listener:listen_on()},
+                       , quicer:listen_on()},
                        pid()}].
 listeners() ->
   quicer_listener_sup:listeners().
@@ -991,7 +990,7 @@ listeners() ->
 %% @doc List listener with app name
 -spec listener(quicer_listener:listener_name()
               | {quicer_listener:listener_name(),
-                 quicer_listener:listen_on()}) -> {ok, pid()} | {error, not_found}.
+                 quicer:listen_on()}) -> {ok, pid()} | {error, not_found}.
 listener(Name) ->
   quicer_listener_sup:listener(Name).
 
@@ -1001,7 +1000,7 @@ get_listeners() ->
   quicer_nif:get_listeners().
 
 %% @doc Get a list of listeners under registration handle
--spec get_listeners(Reg | global) -> quicer_nif:get_listeners(Reg).
+-spec get_listeners(reg_handle() | global) -> quicer_nif:get_listeners().
 get_listeners(global) ->
   quicer_nif:get_listeners();
 get_listeners(Reg) ->
@@ -1014,21 +1013,21 @@ get_connections() ->
   quicer_nif:get_connections().
 
 %% @doc Get a list of connections under registration handle
--spec get_connections(Reg | global) -> quicer_nif:get_connections(Reg).
+-spec get_connections(reg_handle() | global) -> quicer_nif:get_connections().
 get_connections(global) ->
   quicer_nif:get_connections();
 get_connections(Reg) ->
   quicer_nif:get_connections(Reg).
 
--spec get_conn_owner(C) -> quicer_nif:get_conn_owner(C).
+-spec get_conn_owner(connection_handle()) -> quicer_nif:get_owner().
 get_conn_owner(Conn) ->
   quicer_nif:get_conn_owner(Conn).
 
--spec get_stream_owner(S) -> quicer_nif:get_stream_owner(S).
+-spec get_stream_owner(stream_handle()) -> quicer_nif:get_owner().
 get_stream_owner(Stream) ->
   quicer_nif:get_stream_owner(Stream).
 
--spec get_listener_owner(L) -> quicer_nif:get_listener_owner(L).
+-spec get_listener_owner(listener_handle()) -> quicer_nif:get_owner().
 get_listener_owner(Listener) ->
   quicer_nif:get_listener_owner(Listener).
 
diff --git a/src/quicer_listener.erl b/src/quicer_listener.erl
index 3b299ad2..085e0745 100644
--- a/src/quicer_listener.erl
+++ b/src/quicer_listener.erl
@@ -33,9 +33,9 @@
                , alpn :: [string()]
                }).
 
+-export_type([listener_name/0]).
+
 -type listener_name() :: atom().
--type listen_on() :: inet:port_number() | string(). %% "127.0.0.1:8080"
--type listener_opts() :: map().
 
 %%%===================================================================
 %%% API
@@ -47,7 +47,7 @@
 %% @end
 %%--------------------------------------------------------------------
 -spec start_link(Name :: listener_name(),
-                 ListenOn :: listen_on(),
+                 ListenOn :: quicer:listen_on(),
                  Options ::
                    { quicer:listener_opts()
                    , quicer:conn_opts()
diff --git a/src/quicer_nif.erl b/src/quicer_nif.erl
index fbd315e0..4d931d1f 100644
--- a/src/quicer_nif.erl
+++ b/src/quicer_nif.erl
@@ -67,6 +67,28 @@
 %% for test
 -export([init/1]).
 
+
+-export_type([ abi_version/0,
+               new_registration/0,
+               shutdown_registration/0,
+               close_registration/0,
+                get_registration_name/0,
+                get_listeners/0,
+               get_connections/0,
+               get_owner/0
+             ]).
+
+%% NIF fuction return types
+-type abi_version() :: integer().
+-type new_registration() :: {ok, reg_handle()} | {error, atom_reason()}.
+-type shutdown_registration() :: ok | {error, badarg}.
+-type close_registration() :: ok | {error, badarg}.
+-type get_registration_name() :: {ok, string()} | {error, badarg}.
+-type get_listeners() :: [listener_handle()].
+-type get_connections() :: [connection_handle()].
+-type get_owner() :: {ok, pid()} | {error, undefined | badarg}.
+
+
 %% @NOTE: In embedded mode, first all modules are loaded. Then all on_load functions are called.
 -on_load(init/0).
 
@@ -75,7 +97,7 @@
 -include("quicer_types.hrl").
 -include("quicer_vsn.hrl").
 
--spec abi_version() -> integer().
+-spec abi_version() -> abi_version().
 abi_version() ->
   ?QUICER_ABI_VERSION.
 
@@ -144,25 +166,24 @@ reg_close() ->
   erlang:nif_error(nif_library_not_loaded).
 
 
--spec new_registration(Name::string(), registration_profile()) ->
-          {ok, reg_handle()} | {error, atom_reason()}.
+-spec new_registration(Name::string(), Profile :: registration_profile()) -> new_registration().
 new_registration(_Name, _Profile) ->
   erlang:nif_error(nif_library_not_loaded).
 
--spec shutdown_registration(reg_handle()) -> ok | {error | badarg}.
+-spec shutdown_registration(reg_handle()) -> shutdown_registration().
 shutdown_registration(_Handle) ->
   erlang:nif_error(nif_library_not_loaded).
 
 -spec shutdown_registration(reg_handle(), IsSilent::boolean(), ErrorCode::uint64())
-                           -> ok | {error | badarg}.
+                           -> shutdown_registration().
 shutdown_registration(_Handle, _IsSilent, _ErrorCode) ->
   erlang:nif_error(nif_library_not_loaded).
 
--spec close_registration(reg_handle()) -> ok | {error | badarg}.
+-spec close_registration(reg_handle()) -> close_registration().
 close_registration(_Handle) ->
   erlang:nif_error(nif_library_not_loaded).
 
--spec get_registration_name(reg_handle()) -> {ok, string()} | {error, badarg}.
+-spec get_registration_name(reg_handle()) -> get_registration_name().
 get_registration_name(_Handle) ->
   erlang:nif_error(nif_library_not_loaded).
 
@@ -306,27 +327,27 @@ controlling_process(_H, _P) ->
   erlang:nif_error(nif_library_not_loaded).
 
 -spec peercert(connection_handle()  | stream_handle()) ->
-        {ok, Cert :: public_key:der_encoded()} | {error, any()}.
+        {ok, CertDerEncoded :: binary()} | {error, any()}.
 peercert(_Handle) ->
   erlang:nif_error(nif_library_not_loaded).
 
--spec get_conn_owner(connection_handle()) -> {ok, pid()} | {error, undefined | badarg}.
+-spec get_conn_owner(connection_handle()) -> get_owner().
 get_conn_owner(_) ->
   erlang:nif_error(nif_library_not_loaded).
 
--spec get_stream_owner(connection_handle()) -> {ok, pid()} | {error, undefined | badarg}.
+-spec get_stream_owner(connection_handle()) -> get_owner().
 get_stream_owner(_) ->
   erlang:nif_error(nif_library_not_loaded).
 
--spec get_listener_owner(listener_handle()) -> {ok, pid()} | {error, undefined | badarg}.
+-spec get_listener_owner(listener_handle()) -> get_owner().
 get_listener_owner(_) ->
   erlang:nif_error(nif_library_not_loaded).
 
--spec get_listeners() -> [listener_handle()].
+-spec get_listeners() -> get_listeners().
 get_listeners() ->
   erlang:nif_error(nif_library_not_loaded).
 
--spec get_listeners(reg_handle()) -> [listener_handle()] | {error, badarg}.
+-spec get_listeners(reg_handle()) -> get_listeners().
 get_listeners(_) ->
   erlang:nif_error(nif_library_not_loaded).