Facebook is introducing a new “cross device reporting” feature that allows help identify what device a Facebook ad was seen.

Why would this be necessary, you may ask? Because say for example you see a Facebook ad on your phone for a shirt and then bought that shirt 18 hours later on your desktop, should the mobile ad get the credit?

The tracking is made possible via a small snippet of code called a “conversion pixel.” Advertisers who want to see what ads consumers were exposed to can put the conversion pixel into a site or app. Using the tool, marketers will be able to see how many people converted. Facebook also has an option to target an audience that’s similar to the consumers who converted.

Facebook claims that 32% of consumers who “showed an interest” in Facebook ads on mobile wound up buying something via a desktop site within 28 days, the so the new service will help identify where exactly the ads were spotted.

Watch the video above for more insight and check out the full story on Mashable.