This extension is developed to be used only on Read the Docs. If you are building your documentation locally, this extension will degrade gracefully. However, if you have a local instance of Read the Docs running, you can make this extension work by building your documentation with it by following the instructions on the Development page.
Install the package
Then, enable this extension by adding it to your
# conf.py extensions = [ # ... other extensions 'sphinx_search.extension', ]
After installing the package and adding it to your
build your documentation again on Read the Docs and you can see the search
UI in your documentation.