snippet-mode

snippet-mode: the per-buffer snippet gate — C-x C-s expands directly, and it brings the snippet completion source with it.

The gate that decides whether snippets are available in a buffer.

It does two things:

• Binds <C-x><C-s> in Insert mode — expand the snippet whose trigger is before the cursor, directly, without going through the completion popup.
• Brings snippet-completion-mode with it, so snippet candidates appear in the completion popup alongside buffer words, tree-sitter symbols, and LSP results. You never activate that one separately.

Once a snippet is expanding, a third mode takes over the placeholder navigation — see active-snippet-mode.

Which buffers get it

snippet.activation decides. The default is global — every writable buffer. Set it to restrict snippets to the languages in snippet.languages:

:set snippet.activation=languages
:customize snippet

Both options are real and registered, so :customize snippet lists them with their current values.

The three-mode split

It's worth knowing why this is three modes rather than one, because it explains what :describe-mode will show you:

The last one is only active during an expansion, which is what lets <Tab> mean "next placeholder" there without meaning that everywhere else.

See also

• completion — the popup snippets appear in.