Underline Text on iPhone: Which Apps Actually Let You
Last updated July 19, 2026
You can underline text on iPhone, but only in apps that support text formatting, like Messages, Notes, and Mail.
Select the words, then pick Underline from the format options. There is no secret Settings switch to turn on, despite what some old guides claim.
Underline Text in a Message
The Messages app now supports formatting, so you can underline part of an iMessage.
- Type your message, but do not send it yet.
- Press and hold a word, then drag the blue handles to cover the text you want.
- In the menu that appears, tap the arrow until you see the format options.
- Tap Underline. The selected words gain a line beneath them.
You can add Bold, Italic, or Strikethrough the same way. This works on iMessage, the blue bubble chats between Apple devices.
Underline Text in the Notes App
- Open a note and type your text.
- Press and hold to select the words you want.
- Tap the format option (marked BIU) in the popover, or tap the Aa button above the keyboard.
- Tap the underline icon, the U with a line under it.
The underline stays with the note across all your Apple devices.
Underline Text in Mail
- Start an email and type your text.
- Select the words you want to underline.
- Tap the arrow in the selection menu, then tap BIU (Bold, Italic, Underline).
- Tap Underline.
The same steps work in Pages and other Apple apps that handle rich text.
Why Some Apps Will Not Underline
Not every app supports underline, and that is normal.
WhatsApp lets you bold, italicize, and strikethrough text, but it has no underline option at all.
The post boxes in Instagram and X have no built in formatting either. There is no true underline in them, only workarounds that paste odd looking characters.
If an app shows no format menu when you select text, it does not support underline.
What About the Old Settings Trick?
Some older guides say to turn on underline in Settings, General, then Accessibility. That switch does not exist.
Underline lives in each app’s format menu, not in a global setting. If a guide sends you to Accessibility for underline, it is wrong.
Making Text Stand Out in a Plain Text
A plain green bubble SMS has no formatting, so there is no real underline there.
To add emphasis in a plain text, capital letters or an emoji are your only options. For anything richer, switch to iMessage, Notes, or Mail. If your keyboard gets in the way while you format, here is how to make the iPhone keyboard go away.
Frequently Asked Questions
Can you underline text in an iMessage?
Yes. Select the text, open the format options, and tap Underline. This works on iMessage between Apple devices in current iOS. It does not carry over on a plain SMS to an Android phone.
How do I underline in the iPhone Notes app?
Select the text, tap the format option or the Aa button, then tap the underline icon.
Does WhatsApp let you underline text?
No. WhatsApp supports bold, italic, and strikethrough, but not underline. There is no built in underline in WhatsApp.
Why is there no underline option when I select text?
The app does not support text formatting. Underline only appears in apps with a format menu, like Messages, Notes, Mail, and Pages. You can still add message effects in iMessage for a different kind of emphasis.