Twitter adds option to upload and view high-quality images on Android and iOS
More than a month after the original announcement, Twitter confirmed that that the option to upload and view 4K images on Android and iOS is now available for everyone. To start using the new feature, make sure to adjust your preferences in “Data usage” settings, especially if you're on a capped data plan.
You'll probably have to wait for Twitter to roll out the new option to your phone, or you could try updating the app via Google Play Store or App Store. Once you see the option in the Data usage settings, you'll be able to view and upload images at resolutions up to 4096 x 4096 on Twitter's mobile app.