ionicons

Ionicons is a free collection of over 1,300 icons designed to look great in mobile and web apps. Instead of having to find or design your own icons, you can drop a simple HTML tag into your app and instantly display a polished, professional-looking icon. The icons come in different visual styles — filled, outlined, and sharp — so you can match the look and feel of iOS apps, Android apps, or your own design.

Using Ionicons is straightforward. You add a line of code to load the icon library, then use tags like ` to show an icon. The system is smart about performance: it only downloads the icons your page actually displays, and it skips icons that are hidden below the fold on the user's screen. You can also use your own custom SVG files if you need something the library doesn't have.

The icons are highly customizable. You can change their size using CSS, pick any color you want, and adjust how thick the outline strokes are on outlined variants. If you're building an app that needs to look native on both iOS and Android, Ionicons lets you specify different icon versions for each platform with just an attribute like ios="heart-outline" md="heart-sharp"`. This means your app can automatically show the right icon style depending on what device the user is on.

Ionicons was created by the Ionic team for their Ionic app-building framework, but it's completely free and open-source under an MIT license, so anyone can use it for personal or commercial projects. While it's especially popular with Ionic developers, any web or app project can benefit from this ready-made icon set — it saves time and ensures your interface looks consistent and polished.