We use travis-sphinx to generate & deploy HTML documentation.

$ cd <espnet_root>
$ pip install -r doc/requirements.txt

You can generate local HTML manually using sphinx Makefile

$ cd <espnet_root>/doc
$ make html

index.html will be created at doc/_build/html/index.html

or using travis-sphinx

$ cd <espnet_root>
$ travis-sphinx build --source=doc --nowarn

index.html will be created at doc/build/index.html

When your PR is merged into master branch, our Travis-CI will automatically deploy your sphinx html into https://espnet.github.io/espnet/ by travis-sphinx deploy.