diff --git a/.ci/fvt_tests/http_server/rebar.config b/.ci/fvt_tests/http_server/rebar.config
index 314679264..4085df159 100644
--- a/.ci/fvt_tests/http_server/rebar.config
+++ b/.ci/fvt_tests/http_server/rebar.config
@@ -1,5 +1,7 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [debug_info]}.
-{deps, 
+{deps,
  [
     {minirest, {git, "https://github.com/emqx/minirest.git", {tag, "0.3.6"}}}
  ]}.
diff --git a/apps/emqx/rebar.config b/apps/emqx/rebar.config
index 4ec68d585..ff2e84315 100644
--- a/apps/emqx/rebar.config
+++ b/apps/emqx/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [warn_unused_vars,warn_shadow_vars,warn_unused_import,
             warn_obsolete_guard,compressed]}.
 
diff --git a/apps/emqx/rebar.config.script b/apps/emqx/rebar.config.script
index 7b60d1ae0..cb6bab674 100644
--- a/apps/emqx/rebar.config.script
+++ b/apps/emqx/rebar.config.script
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 IsCentos6 = fun() ->
                 case file:read_file("/etc/centos-release") of
                     {ok, <<"CentOS release 6", _/binary >>} ->
diff --git a/apps/emqx_authn/rebar.config b/apps/emqx_authn/rebar.config
index 582b92c0b..d17f1fb90 100644
--- a/apps/emqx_authn/rebar.config
+++ b/apps/emqx_authn/rebar.config
@@ -1,6 +1,9 @@
-{deps, [ {emqx, {path, "../emqx"}}
-       , {emqx_connector, {path, "../emqx_connector"}}
-       ]}.
+%% -*- mode: erlang -*-
+
+{deps,
+ [ {emqx, {path, "../emqx"}}
+ , {emqx_connector, {path, "../emqx_connector"}}
+ ]}.
 
 {edoc_opts, [{preprocess, true}]}.
 {erl_opts, [warn_unused_vars,
diff --git a/apps/emqx_authz/rebar.config b/apps/emqx_authz/rebar.config
index fc8329542..2e33f41d5 100644
--- a/apps/emqx_authz/rebar.config
+++ b/apps/emqx_authz/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [debug_info, nowarn_unused_import]}.
 {deps, [ {emqx, {path, "../emqx"}}
        , {emqx_connector, {path, "../emqx_connector"}}
diff --git a/apps/emqx_auto_subscribe/rebar.config b/apps/emqx_auto_subscribe/rebar.config
index 91cdd39d9..84fadddbc 100644
--- a/apps/emqx_auto_subscribe/rebar.config
+++ b/apps/emqx_auto_subscribe/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [debug_info]}.
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
diff --git a/apps/emqx_conf/rebar.config b/apps/emqx_conf/rebar.config
index 35563d233..86cbfc40b 100644
--- a/apps/emqx_conf/rebar.config
+++ b/apps/emqx_conf/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [debug_info]}.
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
diff --git a/apps/emqx_connector/rebar.config b/apps/emqx_connector/rebar.config
index 0ffae9f7c..1865f8f49 100644
--- a/apps/emqx_connector/rebar.config
+++ b/apps/emqx_connector/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [
   nowarn_unused_import,
   debug_info
diff --git a/apps/emqx_dashboard/rebar.config b/apps/emqx_dashboard/rebar.config
index bd765fa4b..7dc78ebb0 100644
--- a/apps/emqx_dashboard/rebar.config
+++ b/apps/emqx_dashboard/rebar.config
@@ -1,6 +1,9 @@
-{deps, [ {typerefl, {git, "https://github.com/k32/typerefl", {tag, "0.8.6"}}}
-       , {emqx, {path, "../emqx"}}
-       ]}.
+%% -*- mode: erlang -*-
+
+{deps,
+ [ {typerefl, {git, "https://github.com/k32/typerefl", {tag, "0.8.6"}}}
+ , {emqx, {path, "../emqx"}}
+ ]}.
 
 {edoc_opts, [{preprocess, true}]}.
 {erl_opts, [warn_unused_vars,
diff --git a/apps/emqx_gateway/rebar.config b/apps/emqx_gateway/rebar.config
index c94a84de9..74d66e182 100644
--- a/apps/emqx_gateway/rebar.config
+++ b/apps/emqx_gateway/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [debug_info]}.
 {deps, [
   {emqx, {path, "../emqx"}},
diff --git a/apps/emqx_machine/rebar.config b/apps/emqx_machine/rebar.config
index 07646091a..528efecb6 100644
--- a/apps/emqx_machine/rebar.config
+++ b/apps/emqx_machine/rebar.config
@@ -1,2 +1,4 @@
+%% -*- mode: erlang -*-
+
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
diff --git a/apps/emqx_management/rebar.config b/apps/emqx_management/rebar.config
index 0cc5ace2a..f75bd9ce5 100644
--- a/apps/emqx_management/rebar.config
+++ b/apps/emqx_management/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
 
diff --git a/apps/emqx_modules/rebar.config b/apps/emqx_modules/rebar.config
index 07646091a..3f84bb8df 100644
--- a/apps/emqx_modules/rebar.config
+++ b/apps/emqx_modules/rebar.config
@@ -1,2 +1,5 @@
-{deps, [ {emqx, {path, "../emqx"}}
-       ]}.
+%% -*- mode: erlang -*-
+
+{deps,
+ [ {emqx, {path, "../emqx"}}
+ ]}.
diff --git a/apps/emqx_plugin_libs/rebar.config b/apps/emqx_plugin_libs/rebar.config
index 07646091a..528efecb6 100644
--- a/apps/emqx_plugin_libs/rebar.config
+++ b/apps/emqx_plugin_libs/rebar.config
@@ -1,2 +1,4 @@
+%% -*- mode: erlang -*-
+
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
diff --git a/apps/emqx_plugins/rebar.config b/apps/emqx_plugins/rebar.config
index 07646091a..528efecb6 100644
--- a/apps/emqx_plugins/rebar.config
+++ b/apps/emqx_plugins/rebar.config
@@ -1,2 +1,4 @@
+%% -*- mode: erlang -*-
+
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
diff --git a/apps/emqx_prometheus/rebar.config b/apps/emqx_prometheus/rebar.config
index 61e2662bf..bd611d4eb 100644
--- a/apps/emqx_prometheus/rebar.config
+++ b/apps/emqx_prometheus/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {deps,
  [ {emqx, {path, "../emqx"}},
    %% FIXME: tag this as v3.1.3
diff --git a/apps/emqx_psk/rebar.config b/apps/emqx_psk/rebar.config
index 3def1d00e..4bdb7b3c6 100644
--- a/apps/emqx_psk/rebar.config
+++ b/apps/emqx_psk/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
 
diff --git a/apps/emqx_resource/rebar.config b/apps/emqx_resource/rebar.config
index 4e88043de..194aa0cd4 100644
--- a/apps/emqx_resource/rebar.config
+++ b/apps/emqx_resource/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [ debug_info
            , nowarn_unused_import
            %, {d, 'RESOURCE_DEBUG'}
@@ -14,4 +16,3 @@
 
 {deps, [ {jsx, {git, "https://github.com/talentdeficit/jsx", {tag, "v3.1.0"}}}
        ]}.
-
diff --git a/apps/emqx_retainer/rebar.config b/apps/emqx_retainer/rebar.config
index e5b53f1be..0e363fb63 100644
--- a/apps/emqx_retainer/rebar.config
+++ b/apps/emqx_retainer/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
 
diff --git a/apps/emqx_rule_engine/rebar.config b/apps/emqx_rule_engine/rebar.config
index 56a64b436..72be78a1d 100644
--- a/apps/emqx_rule_engine/rebar.config
+++ b/apps/emqx_rule_engine/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
 
diff --git a/apps/emqx_slow_subs/rebar.config b/apps/emqx_slow_subs/rebar.config
index 07646091a..528efecb6 100644
--- a/apps/emqx_slow_subs/rebar.config
+++ b/apps/emqx_slow_subs/rebar.config
@@ -1,2 +1,4 @@
+%% -*- mode: erlang -*-
+
 {deps, [ {emqx, {path, "../emqx"}}
        ]}.
diff --git a/apps/emqx_statsd/rebar.config b/apps/emqx_statsd/rebar.config
index d54b3e25f..b6ad169f8 100644
--- a/apps/emqx_statsd/rebar.config
+++ b/apps/emqx_statsd/rebar.config
@@ -1,3 +1,5 @@
+%% -*- mode: erlang -*-
+
 {erl_opts, [debug_info]}.
 {deps, [ {emqx, {path, "../emqx"}}
        , {estatsd, {git, "https://github.com/emqx/estatsd", {tag, "0.1.0"}}}