In response to a request made by users, Twitter produced a Basque version in 2012 and since then there has been an option to use the Twitter interface in Basque.
UMAP is the website that gathers and filters the activity of Basque-speaking Twitter users. According to it, there were a total of 13,500 active users using Basque in 2017. As far as the tweets are concerned, these active users in the community sent 6,480,109 tweets (2,400,000 in Basque). The number of Twitter users writing mainly in Basque (more than 75% of the content in Basque) has been 2,2302, 17% of the total.
For further information: https://umap.eus/