In an effort to improve transparency (although to be fair there’s not an awful lot be improved on) they have also made it clear how much data they collect on users.
In short, this includes your tweets and the metadata provided with them as well as log information such as when, where and from what device you tweet. There’s also more techincal information such as your browser type, operating system, referring web page, mobile carrier, search terms and cookie information.
Log in information is purged after 18 months and after a maximum of ten days Twitter will start to delete or aggregate your widget data. They have also come out in support of the Do Not Track (DNT) function found in a number of web browsers. This stops the tailoring of accounts based on other websites visited with the Twitter buttons displayed.
For a more in depth round up of the changes, click here.
Source: PC World