Twitter on Wednesday unveiled a new tool that allows marketers to disseminate targeted messages based on the content of users' tweets. Until now, Twitter has been able to decipher a user's interests largely by analyzing the list of accounts he or she follows, otherwise known as the "interest graph."

The new tool allows marketers using Twitter to delve into the content of a user's tweets to show the most relevant ads. Available today in all languages and markets where Twitter Ads are supported is keyword targeting in timelines.

Available in the full Twitter Ads UI and through the Ads API, this new feature enables advertisers to reach users based on the keywords in their recent Tweets and the Tweets with which users recently engaged. This is an important new capability - especially for those advertisers looking for signals of intent - because it lets marketers reach users at the right moment, in the right context.

For example: let's say a user tweets about enjoying the latest album from their favorite band, and it so happens that band is due to play a concert at a local venue. That venue could now run a geotargeted campaign using keywords for that band with a Tweet containing a link to buy the tickets. That way, the user who tweeted about the new album may soon see that Promoted Tweet in their timeline letting them know tickets are for sale in their area.

Twitter said that users would not see any difference in their use of Twitter - ads will not be shown more frequently in timelines, and users can still dismiss Promoted Tweets they don't find relevant.

The push to refine its advertising products comes as Twitter prepares for an IPO as early as 2014.

Google's search ad technology has proved effective because it shows relevant ads based on precisely what a user has searched for.

Facebook also shows ads based on what a user has "liked," among many other signals.