Lucide Icons 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.
| Lucide Icons | Fluent UI Icons | |
|---|---|---|
| Icons | 1,979 | 20,170 |
| Visual variants per concept | 1 — outline only | 2 — regular and filled |
| Design grid | 24×24 | 12–48 |
| License | ISC | MIT |
| Attribution required | No | No |
| Official React package | lucide-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.
SaaS dashboards, developer tools, documentation sites, and any product that wants a calm, neutral, geometric icon language. Lucide is particularly strong in dense interfaces because its uniform stroke weight stays legible at 16px and 20px.
Consider otherwise if: If you need multiple weights from one library, Phosphor offers six. If you need filled icons, IconPark Solid or Material Design Icons are better choices, since Lucide is outline-only.
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.
Lucide Icons contains 1,979 icons and Fluent UI Icons contains 20,170. Lucide began as a fork of Feather Icons when Feather's release cadence slowed and community pull requests began to pile up. Rather than let the project stall, contributors created Lucide with an explicit commitment to community governance and regular releases. It has since grown well past its parent: 1,979 icons against Feather's 286.
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.
Lucide Icons is released under ISC. Functionally equivalent to MIT — 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 Lucide Icons or Fluent UI Icons, or browse every library comparison.
Both have first-party React packages: lucide-react and @fluentui/react-icons. Lucide 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.
Lucide Icons has 1,979 icons and Fluent UI Icons has 20,170. Fluent UI Icons is larger by about 919%. 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 — Lucide 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.
Lucide Icons is ISC: Functionally equivalent to MIT — 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.
Lucide Icons 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. Lucide 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.