Iconoir and Fluent UI Icons are two of the most widely used open-source icon sets. Both are free, both ship framework packages, and both will look perfectly reasonable in a product UI — which is exactly why the choice is annoying. This page puts the two side by side using the actual artwork and the real numbers.
| Iconoir | Fluent UI Icons | |
|---|---|---|
| Icons | 2,020 | 20,170 |
| Visual variants per concept | 1 — outline only | 2 — regular and filled |
| Design grid | 24×24 | 12–48 |
| License | MIT | MIT |
| Attribution required | No | No |
| Official React package | iconoir-react | @fluentui/react-icons |
Every pair below is the same concept rendered from each library's own source files. This is the part you cannot get from a written review — the difference in stroke weight, corner rounding and optical size is the thing you will actually notice in your interface.
Side projects, startups, and open-source tools that need breadth without a licensing conversation. Iconoir is a reliable default when you do not yet know which icons you will need.
Consider otherwise if: Lucide has stronger governance and a larger community; Tabler has roughly triple the icon count. Iconoir's advantage is that nothing is ever paywalled.
Enterprise applications, Microsoft 365 integrations, and products that already follow Fluent or need extremely broad coverage. The count alone means you will rarely need to look elsewhere.
Consider otherwise if: The size is also a drawback — with 20,170 icons, maintaining visual consistency across a product takes more discipline. Lucide and Heroicons are far easier to keep coherent.
Iconoir contains 2,020 icons and Fluent UI Icons contains 20,170. Iconoir started as one designer's answer to a simple frustration: good icon libraries kept gating the useful icons behind a paid tier. The set is 2,020 icons on a 24×24 grid with a 1.5px stroke, and there is no premium version — every icon is free, forever.
Fluent UI Icons is Microsoft's icon library for the Fluent Design System, and at 20,170 icons it is the largest set indexed on IconStash. The icons are drawn across multiple sizes from 12px to 48px and in Regular and Filled styles.
Iconoir is released under MIT. Commercial use, modification and redistribution with no attribution required.
Fluent UI Icons is released under MIT. Commercial use, modification and redistribution with no attribution required.
You do not have to commit to one. IconStash indexes both libraries, so you can search a concept once and see how each set drew it, then export SVG or PNG at any size and colour. Start with Iconoir or Fluent UI Icons, or browse every library comparison.
Both have first-party React packages: iconoir-react and @fluentui/react-icons. Iconoir has the smaller catalogue, so for a React app the practical difference is coverage and visual style rather than integration effort. Both tree-shake, so bundle size tracks the number of icons you import, not the size of the library.
Iconoir has 2,020 icons and Fluent UI Icons has 20,170. Fluent UI Icons is larger by about 899%. Raw count is not the whole story though — a 20,000-icon set with many near-duplicate variants can be slower to search than a tightly edited 2,000-icon set.
You can, but it usually looks wrong. Each library draws to its own grid and stroke weight — Iconoir uses 24×24 and Fluent UI uses 12–48 — so icons from both sit slightly differently next to each other. If you must mix them, keep each library to a distinct area of the interface rather than interleaving them in the same toolbar.
Iconoir is MIT: Commercial use, modification and redistribution with no attribution required. Fluent UI Icons is MIT: Commercial use, modification and redistribution with no attribution required. Neither requires payment, but attribution rules differ, so check before shipping in a product where credit is inconvenient.
Iconoir offers outline only; Fluent UI Icons offers regular and filled. If you need to express selected and unselected states with the same glyph, the library with more variants saves you from importing a second set.
At 16px, stroke weight and counter size matter more than coverage. Iconoir draws on a 24×24 grid and Fluent UI on 12–48. Libraries that redraw per size rather than scaling — such as Fluent UI — generally hold up best. The reliable test is to preview both at your actual render size, which you can do on any icon page on IconStash.