Icons8's icon catalog is a large, heterogeneous aggregator (1.5M+ icons) spanning dozens of distinct named style families, Fluency, iOS, Windows 11, Doodle, and many more, produced in-house by one company rather than pulled from outside contributors.
The breadth covers nearly any icon concept in nearly any visual style, and because everything is produced by one company, licensing terms are uniform across the whole catalog, unlike aggregators that mix many outside contributors' terms.
Good when you need to search broadly across many aesthetics rather than commit to one; for a small, tightly cohesive set, pick one of Icons8's individual style families (like Glyph Neue) instead.
Free icons require a visible link back to Icons8; a paid subscription (from $13/month) removes that requirement and opens up higher-resolution exports and exclusive sets.
A library of 120,000+ free icons, with paid options for higher-res and exclusive sets.