Firefox for Android supports sending text (SMS) or multimedia (MMS) messages directly from the web pages that offer it.
- Tap on the SMS or MMS link (usually a phone number) on the web page to launch the messaging app.
- If you're using this feature for the first time, a prompt will ask you to choose an app. Choose your phone's messaging app, which for most devices is Messenger or Hangouts.
- Your messaging app will open and automatically fill in the number and message that was on the web page.
- Edit as needed and tap Send.