With iOS 12 & macOS Mojave Safari (finally) allows you to see tab icons which is useful when you have a bunch open.
How to enable favicon in Safari in iOS on iPad & iPhone
- Open the Settings App.
- Head into Settings > Safari.
- Scroll down until you see the Show Icons in Tabs option.
- Make sure Show Tab Bar is also on.
- Slide the slider across.
How to enable favicon in Safari in macOS
- Open Safari.
- Select Safari in the menu bar, and then Preferences.
- Click Tabs from the list.
- Check the Show website icons in tabs checkbox.