fzf

fzf is a general-purpose command-line fuzzy finder — it reads any list, narrows it down as you type a few of the letters in any order, and prints what you picked. Pipe something in, or let it walk the files for you.

The demo starts in git's own source tree, so there is plenty to search. Run fzf and type bltcommit to land on builtin/commit.c, add --preview 'cat {}' to see a file before choosing it, or press CTRL-R to fuzzy-search the shell's history. The VM is private to your browser tab; nothing you type leaves it.