Heroicons 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.
| Heroicons | Fluent UI Icons | |
|---|---|---|
| Icons | 1,297 | 20,170 |
| Visual variants per concept | 2 — outline and solid | 2 — regular and filled |
| Design grid | 16/20/24 | 12–48 |
| License | MIT | MIT |
| Attribution required | No | No |
| Official React package | @heroicons/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.
Tailwind CSS projects of any size, and teams that want their icons styled with the same utilities as the rest of their markup. The three drawn sizes also make Heroicons a good fit for interfaces with a strict type and spacing scale.
Consider otherwise if: Outside the Tailwind ecosystem the utility-class ergonomics matter less, and Lucide or Tabler give you more icons. For dense 15px-scale interfaces, Radix Icons is drawn specifically for that.
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.
Heroicons contains 1,297 icons and Fluent UI Icons contains 20,170. Heroicons is made by the team behind Tailwind CSS, and it is designed to drop straight into Tailwind projects. The 1,297 icons ship in outline and solid variants, each available at 16px, 20px, and 24px — three sizes that are drawn separately rather than scaled, so optical weight stays correct at each one.
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.
Heroicons 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 Heroicons or Fluent UI Icons, or browse every library comparison.
Both have first-party React packages: @heroicons/react and @fluentui/react-icons. Heroicons 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.
Heroicons has 1,297 icons and Fluent UI Icons has 20,170. Fluent UI Icons is larger by about 1455%. 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 — Heroicons uses 16/20/24 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.
Heroicons 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.
Heroicons offers outline and solid; 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. Heroicons draws on a 16/20/24 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.