Last week, Twitter turned off the ability to receive SMS messages containing the text of new tweets. The feature was disabled in all but “a few countries” that rely on the feature.

This won’t be a huge deal for the vasty majority of Twitter users who access the service via the app or website. But there are already complaints from some people who still used SMS to read tweets. One business, DansDeals, said it relied on the feature to alert readers to sales.

The change largely marks the end of an era for Twitter: when the service launched, it was built around SMS. Its original 140-character limit was tailored to text message sizes, and you were meant to send and receive new tweets entirely over SMS. That hasn’t been the primary way to use Twitter for a long time, though, as more people bought smartphones and could use the mobile app.

Twitter disabled the ability to compose tweets via text last September due to security issues. Hackers gained access to the phone number of Twitter CEO Jack Dorsey, at which point, they were able to use the SMS feature to tweet from his account. Twitter promptly disabled sending tweets via SMS for all but “a few locations.”

This latest update is also said to be about helping “people keep their accounts safe,” according to a Twitter spokesperson. It’s not entirely clear what the risk is when receiving tweets, rather than sending them, but Twitter has been interested in phasing this feature out for some time now. If people receive tweets over SMS, it can’t display ads to them, so it would much rather have people checking the app.

“We turned off the remainder of our Twitter via SMS feature, except for a few countries that rely on it to use Twitter,” the Twitter spokesperson said. Twitter will still send “important SMS messages” for securing accounts, like authentication codes.