Emacs: Completion in the buffer with completion-at-point-functions

Protesilaos Stavrou explains how Emacs performs in-buffer completion and how to configure frontends like Corfu and Company.

In this ~22-minute video I explain how Emacs performs completion in a buffer. I cover what happens behind the scenes with the variable completion-at-point-functions. Then I also go to the frontends, which affects the modalities of interaction. I cover the built-in Completions buffer, the packages Corfu and Company, and the built-in completion-preview-mode. Finally, I comment at some further length on how to control the grouping of results in the completion-at-point-functions. In that context I also mention the Cape package, as well as some extra functionality that the Company package provide. I wrote an article which covers all of what is in the video as well as code samples. You can read it on my website here: protesilaos.com/codelog/2026-07-19-emacs-completion-at-point…