Companies are now able to search and analyse up to two years of Twitter updates for market research purposes.
Firms can search tweets back to January 2010 in order to plan marketing campaigns, target influential users or even try to predict certain events.
Until today, only the previous 30 days of tweets were available for companies to search. Regular users can access posts from the past seven days.
Private accounts and tweets that have been deleted will not be indexed by the site.
"People have historically used Twitter to communicate with friends and networks in the belief that their tweets will quickly disappear into the ether," argued Gus Hosein, executive director of Privacy International.
Target influential users
Target influential users