A robust icon library is indispensable in product design. A good one should check the following:

✅ 1. Lots of varied icons. I don't wanna waste hours of time designing custom icons (not my strength anyway, and not why clients hire me) when I could be mapping out entire features and flows in that time.

✅ 2. Different weights. Thin and subtle when the icon needs to communicate its purpose with minimal fuss. Thicker variants for big, beefy visuals.

✅ 3. "Fill" variants ready to go. When you favourite an item 🖤, you wanna see the heart fill to communicate that the action has been registered.

✅ 4. Cohesive design aesthetic. All icons should look like they're part of a family. You don't want one icon in one style, and another looking like it belongs to a different website altogether — that looks amateurish.

✅ 5. The icon library must have an easy to browse website, with a big, fat search bar at the top and a list of all the icons below. Then for each icon, the ability to quickly copy the SVG, React code to the clipboard so I can paste in Figma or Visual Studio Code.

To date, the only two libraries that I've used that fit the bill:

Phosphor https://phosphoricons.com/ (9,000+ icons) — it just works™. Elegant and meets all the requirements above.

Material Design Icons https://lnkd.in/gJHCzYCm (2,500+ icons) — tend to look more blocky, which is fine for some brands, but Phosphor Icons are more curved and elegant, so I choose them.

Some more worthy mentions:

Lucide Icons https://lucide.dev/icons look beautiful but they fail on point 3 — they don't offer a "filled" variant for each icon out of the box. And that's a real shame, because aesthetically I think they're my favourite.

Font Awesome icons https://fontawesome.com I've never actually used. Over 60K icons — absolute mega library. $120 per year though. Could never really justify the cost to myself or to a client given that Phosphor got the job done on every project I've worked on so far.

There's a whole bunch of other icon libraries out there but I've found that none of them meet all 5 criteria above.