On Windows, press `Alt + 0178` for `²`
On Mac, press `Option + 00B2` in a Unicode-capable app, or use the Character Viewer to insert `²`
On Linux, use `Ctrl + Shift + U`, type `00B2`, then press `Enter`
On iPhone or Android, long-press `2` on the keyboard to find `²`
In Microsoft Word, type `2`, then apply superscript formatting
In HTML, use `²` for `²`
Copy and paste this character: `²`