Icons8 is a free icon material website, suitable for designing people. There are a large collection of icons in different styles for different projects. The number of icons is huge and the quality is high. Designers don't need to spend a lot of time looking for good materials, because Icons8 are all available.

Steps：

1. Start Icons8, enter the icon theme, here we take Facebook as an example. Press Enter to search.

2. Select the appropriate icon and click Download. The downloaded icon supports two formats: PNG and SVG. The PNG format supports several different sizes, and you can also customize the size by yourself. For example, the custom size in the picture is 560.