If you are developing a website or mobile app, there may be a requirement of different icons that makes the UI of the application attractive and more user friendly. There are a lot of websites from where you can buy icons but if you are looking for open source icons that you can use in your application without a commercial license, Feathericons.com is the right place for you.
Feathericons provide you hundreds of icons in SVG format that you can use without spending a buck in your application. You can directly download SVG icons from the website and also can customize them by changing the colors and dimensions of icons.
You can easily search for the icons on the website and use them in your application as per the requirement. You can also use these icons by adding a CDN library of icons on your website or you can download all icons at once. The detailed description to use the icons on your website can be found here.