Lucide, Tabler Icons, and Phosphor are three of the most recommended open-source icon libraries, and they come up together in almost every "which icon set should I use" thread. All three are permissively licensed, actively maintained upstream, and fully browsable on svgicons.com, so you can compare the actual vectors side by side before committing your project to one visual language.
The numbers and license details below are read from the catalog database that powers this site, not copied from marketing pages. Where the sets differ upstream, the comparison sticks to what ships in the indexed releases.
Quick comparison
Set
Icons here
