You can no longer use Twitter for the most part, as it was originally built for use: over text message.
Last week, Twitter deactivated the ability to receive SMS messages containing new tweet text. In all but "a few countries" which depend on the feature, the feature has been disabled.
To the large majority of Twitter users who access the service via the app or website, this won't be a big deal. But some people who still used SMS to read tweets do still have concerns. One company, DansDeals, said it was relying on the feature to alert readers to sales.
This move marks, in large part, the end of an age for Twitter: it was centered on SMS when the service was launched. Its original 140-character cap was adjusted to text message sizes, and you were expected to send and receive new tweets via SMS entirely. This wasn't, though, the main way to use Twitter for a long time, because more people were purchasing smartphones and could use the mobile app.
Last September, Twitter deactivated the ability to write tweets via text due to security issues. Hackers obtained access to the Twitter CEO's phone number, Jack Dorsey, at which point they were able to tweet from his account using the SMS feature. For all but "a few locations," Twitter immediately deactivated sending tweets via SMS.
According to a Twitter spokesperson, this latest update is also about helping "people keep their accounts safe." It's not entirely clear what the risk is when receiving tweets, rather than sending them, but for some time now Twitter has been interested in phasing out this option. If people receive tweets via SMS, they won't be able to show advertisements to them, so people would much rather have to check 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,” said the Twitter spokesperson . Still, Twitter can send "important SMS messages" to secure accounts, such as authentication codes.