The acronym T9 stands for Text on 9 keys. T9 "predictive texting" is a tool used primarily on non-smartphones (phones with only a nine-key keypad, similar to a telephone) to allow users to text faster and more easily.

If you have a smartphone with a full keyboard today, remember trying to send a text message on your old clamshell phone? It was T9 that made composing messages possible on a small device, bringing texting and email to mobile devices in a way that had never been effective before.

That’s right — most mobile phone users now have smartphones (a Pew Research study reports that in 2019, 81 percent of U.S. adults own a smartphone, compared to just 15 percent who own a non-smartphone mobile phone). But the small size of smartphone keyboards can still make typing messages a hassle, so predictive text (not just T9 predictive text) is still important.

Anyone with a nine-keypad mobile phone will find the T9 to be an essential tool. But even some smartphone users choose to take advantage of it via the various Android or iPhone apps that add a T9 keypad to a device. These users appreciate the larger nine-digit grid and have often developed a certain comfort level with the T9 keypad on previous phones, so they find texting is faster when they use it.