In apps like Pages, TextEdit, Word, or Google Docs, select the text you want to make subscript
Use the app’s subscript command or formatting menu
In Microsoft Word on Mac, press Command + = to toggle subscript
In Google Docs, go to Format > Text > Subscript
In Pages, click Format > Style > Baseline > Subscript
In TextEdit, use Format > Font > Baseline > Lower
If the app supports it, use the keyboard shortcut Command + Control + = for subscript
On Mac, you can also use the Character Viewer to insert special subscript characters
For chemical formulas and math, copy and paste Unicode subscript characters such as ₀ ₁ ₂ ₃ ₄ ₅ ₆ ₇ ₈ ₉