The <> or </> symbol is often associated with “code”. The links are not necessarily to GitHub, it depends on the project configuration.

The documentation is written in Markdown format alongside the implementation of modules and functions.

The ex_doc library is the tool to extract the documentation and produce that nice website (and an ebook too!), and then it can publish the content to hexdocs.pm, a central repository of documentation.

You can also generate documentation for your own projects, even if you never intend to publish it online.

Now, why is it linking to version 1.16.1? I just checked, that is the version locked in phoenix/mix.lock at v1.8.1 · phoenixframework/phoenix · GitHub.

So I think ExDoc is interpreting Plug as a module and conservatively generating a link to the docs at the version the project has been tested with. I don’t know if that behavior is configurable.

ex_doc is the doc generator for Elixir. it will do its best to form links for modules, functions, types and callbacks from the text within backticks. Thats how the docs are generated and how iex is able to introspect documentation too.