diff --git a/.gitignore b/.gitignore
index c69f5fed..671d5390 100644
--- a/.gitignore
+++ b/.gitignore
@@ -83,7 +83,6 @@ node_modules/
 package-lock.json
 erlang_ls.config
 .els_cache/
-./lib-ce/
 # VSCode files
 .vs/
 .vscode/
diff --git a/lib-ce/README.md b/lib-ce/README.md
new file mode 100644
index 00000000..56a60cff
--- /dev/null
+++ b/lib-ce/README.md
@@ -0,0 +1,86 @@
+# EMQX Extra plugin apps
+
+This directory keeps a `plugins` file which defines all the approved
+external plugins from open-source community.
+
+The (maybe broken) symlinks are keept to help testing plugins
+in this umbrella project.
+
+## Add a plugin to the project
+
+Add `plugin_foo` as a rebar3 dependency in `plugins` file.
+
+e.g. For an Erlang plugin named `plugin_foo`:
+
+```
+{erlang_plugins,
+  [ {plugin_foo, {git, "https://github.com/bar/plugin-foo.git", {tag, "0.1.0"}}}
+  ]
+}.
+```
+
+Note: The `-emqx_plugin(?MODULE)` attribute should be added to
+`<plugin-name>_app.erl` file to indicate that this is an EMQX Broker plugin.
+
+For example:
+```erlang
+%% plugin_foo_app.erl
+-emqx_plugin(?MODULE)
+```
+
+## Build a release
+
+```
+$ export EMQX_EXTRA_PLUGINS=plugin_foo,plugin_bar
+$ make
+```
+
+If all goes as expected, there should be two directories in the release:
+
+```
+_build/emqx/rel/emqx/lib/plugin_foo-<..vsn..>/
+```
+
+## Run your code
+
+Start the node (interactive mode)
+
+```
+./_build/emqx/rel/emqx/bin/emqx console
+```
+
+Load the plugin with command:
+
+```
+./_build/emqx/rel/emqx/bin/emqx_ctl plugins load plugin_foo
+```
+
+## Test the plugin
+
+If the plugin is added as a rebar dependency, it should be cloned
+to `_build/default/lib/plugin_foo`.
+
+Before you can test it, you need to make sure there is a symlink
+in `lib-extra` pointing to the clone. For instance, the `emqx_plugin_template`
+plugin is linked like this
+
+`emqx_plugin_template -> ../_build/default/lib/emqx_plugin_template/`
+
+To run its teste cases:
+
+```bash
+./rebar3 eunit --dir lib-extra/plugin_foo
+mkae lib-extra/plugin_foo-ct
+```
+
+NOTE: we should `depth=1` shallow clone into `_build/` directory,
+for plugins being actively developed, you can place the clone in `lib-extra/`
+
+## Caveats
+
+* Elixir dependency in Erlang is not quite nicely supported as incremental builds,
+  meaning you will not be able to edit the code in this project and get recompiled
+  in the next `make` command.
+
+* To have the plugin enabled/loaded by default, you can include it in the template
+  `data/loaded_plugins.tmpl`