Twitter just gave its ads business a major boost

Twitter just announced a major move to boost its ads business: It's starting to show "promoted tweets" to people without active accounts.

That means that when a person who is not logged in to a Twitter account finds a tweet through Google search or by clicking through an embed link in an article, they'll see Twitter's ads on the tweet feed or user profile that they're looking at.

Twitter is just testing this new ad-serving method for now, but it could more than double Twitter's base of monetizable users.

Previously, it could only make money off its 320 million logged-in users, but now it can serve ads to its 500 million logged-out users, too, allowing marketers to reach 820 million people total.

The news comes at a critical time for the company. Twitter shares tanked after its Q3 earnings in large part because the social network's user growth has remained sluggish.

Although Twitter won't be able to charge as much for the ads shown to logged-out users - because marketers won't have as much ad-targeting information about them through their Twitter activity - it will still be a big influx of new revenue.

The company told Re/code that instead of targeting based on a users' interests, Twitter will use the context in which the user discovered a tweet (for example, if they arrived on Twitter through searching "baseball" on Twitter, promoted tweets would relate to baseball).

Twitter's rolling out these tests with selected advertisers first, and the promoted tweets will appear on the desktop web only.