Can I use them commercially?
Yes. Use the icons in apps, websites, products, client work, templates, and anything you sell. There's nothing to pay and no one to ask.
Do I need to credit you?
No. A mention or a link back is appreciated, but it isn't required in your app or on your site.
The MIT license asks one thing: if you redistribute the icon files or the code themselves, for example in an icon package or a library of your own, keep the copyright notice from LICENSE.txt with them.
Can I change the icons?
Yes. Recolor them, resize them, redraw parts, combine them, or convert them to another format. You don't need to share your changes.
What does the license cover?
The icons, in every size and weight, and the code that ships them: the SVG files, icons.json, the command-line tool, and the agent files.
What isn't covered?
The fonts on this site are Polymath, by OH no Type Company. They're licensed for this site only, so they aren't part of the set and you can't reuse them from here.
The name The Standard Icon Set and its logo identify this project. Use the icons freely, but don't present your own product as this set or as made by Morgan Knutson.
Is there a warranty?
No. The icons are provided as they are, without any warranty, as the license says.