You can change the font size in a WhatsApp chat in WhatsApp Settings. The font size on other screens in the app are based on your device settings.
Change font size in a chat
- Open WhatsApp.
- Tap More options.
- Tap Settings > Chats > Font size.
- You can select from Small, Medium, or Large.
Change font size on other screens
- Go to device Settings > Accessibility.
- Tap Font size.
- You can select from Default, Large, or Largest.
Note: Custom fonts aren’t supported.