Octicons is GitHub's own icon set, part of the Primer design system: 377 icons in the current release, each individually tuned (not merely scaled) at 12px, 16px, 24px, and a few logo sizes up to 96px.
Icons tuned separately per pixel size rather than mechanically scaled stay sharper at small sizes like 12px, where a naively-scaled SVG tends to blur or lose detail.
Fits developer tools, code editors, and technical UIs going for the same crisp, minimal look GitHub itself uses.
MIT licensed and free; every SVG uses fill="currentColor" so icons inherit text color automatically, which makes dark-mode theming free with no extra icon variants needed.
