Twitter announced the introduction of ads based on web-surfing activity, which means they will show you ads based on where you had previously been on the Internet.

Called tailored audiences, the feature rolled out in a smaller scale in July, and using it, advertisers can target users who have either visited their website or "shown an interest" in your brand's category on and outside of Twitter.

This means that advertisers can identify people who are in the market for a product. In a blog post announcing tailored audiences, Twitter noted that beta users HubSpot saw a lift in engagement rates of 45% vs. historical average. Krossover, meanwhile, saw a 74% decrease in cost-per-acquisition.

Twitter's stock was up nearly 5% for the day following the announcement.