Twitter is beginning to “experiment” with what they call “tailored ads,” which should look familiar to you and me as email-based and cookie-based retargeting. Before we get into what Twitter’s actually doing here, let’s get two important things out of the way:

First off, these tailored ads are only going to be shown to users in the U.S. Twitter didn’t give any information on any international expansion. Also, you can easily opt out of the new types of advertisements by simply unchecking a box in your account settings.

So here’s what Twitter’s is unveiling: Promoted tweets that are highly targeted to match users who have previously shown interest in the tweet’s content. How is Twitter going to prove previous interest? Well, if you’re on the company’s email list or if you’ve been frequenting their site, that’s a start.

Here’s how Twitter’s Kevin Weil describes it using an example of a florist who wished to target specific customers around Valentine’s day:

How does this work? Let’s say a local florist wants to advertise a Valentine’s Day special on Twitter. They’d prefer to show their ad to flower enthusiasts who frequent their website or subscribe to their newsletter. To get the special offer to those people who are also on Twitter, the shop may share with us a scrambled, unreadable email address (a hash) or browser-related information (a browser cookie ID). We can then match that information to accounts in order to show them a Promoted Tweet with the Valentine’s Day deal. This is how most other companies handle this practice, and we don’t give advertisers any additional user information.

Basically, Twitter is moving into cookie-based and email-based ad retargeting. This is nothing new around the web – it’s just the first time we’ve seen in from Twitter.

As I said before, Twitter is giving users a way to opt-out, however.

Here’s the pertinent part in your accounts settings that allows you to disable these new types of promoted tweets based on “info shared by ad partners”:

Happy 4th weekend, America. If you’ve been looking for fireworks recently, be prepared for some oddly specific tweets aimed in your direction.