Fluent UI Icons

Fluent UI System Icons is Microsoft's official open-source icon set, used across Office, Microsoft 365, Edge, Windows, and Teams, and distributed under an MIT license. The library is unusually large — 19,837 icons spanning 16, 20, 24, 28, 32, and 48-pixel sizes in both Regular (outline) and Filled variants. That per-size, per-weight precision is the point: each variant is hand-tuned for legibility at its target size rather than being a scaled version of a master, which is why Fluent icons stay sharp even at small button sizes. The set is a strong choice for products that already lean Microsoft-aligned, that need to support dense UI surfaces, or that simply want a polished, well-maintained, professionally-drawn set with very broad topical coverage.