We’re still waiting for Sony to give us a glimpse of the PlayStation 5, but Microsoft took the initiative in December of 2019 and surprised us all by revealing the Xbox Series X at The Game Awards. Although we got to see what the front of the console looks like, Microsoft didn’t show us the back of the Xbox, and so everyone has been speculating about ports and features ever since. At least, they were, until a photo of a prototype leaked online.

Late last month, images of the Xbox Series X (or at least an early prototype of the console) were shared on NeoGAF. Brad Sams of Thurrott confirmed that the images were legitimate, but could not figure out what the long, rectangular slot underneath the Ethernet port was for. Weeks later, he finally has an answer.

According to Sams, the mystery port on the back of the Xbox Series X prototype is actually for storage expansion. This information is said to come from sources with knowledge of the company’s plans, and Sams has a pretty good track record when it comes to Microsoft leaks. It’s also worth noting that Thurrott forum goer thereverendslim wrote the following message just a few short days after the photo leaked:

Given that 1) the “debug port” on the Xbox Series X looks to be roughly 31mm x 4mm, 2) that a LinkedIn entry showed Phison’s PS5019-E19T controller being developed for or used by the Series X, 3) that Phison’s datasheet for that controller shows that it can be used in a CFExpress form factor, and that the dimensions of a Type B CFExpress card are 29.8mm x 3.8 mm… Do you think it’s possible that rather than having an internal non-replaceable NVMe-style SSD, they are using Compact Flash Express for the SSD so that you can expand in the future? CFExpress has pretty much only been used in high-end digital cameras up to now, but this would make way more sense to me than that being a “debug port”.

Based on what Sams has heard, this guess might have been spot on, but as Sams notes, CFExpress cards are wildly expensive, with 512GB cards retailing for around $600. That would make additional storage for the Xbox Series X as or more expensive than the console itself, which is hard to imagine. So, either Microsoft believes the prices will drop soon, or, as Sams says, “they have found a way to utilize that style of port with different storage.”

Whatever the case, as the size of games continues to increase, 1 or 2TB of internal storage isn’t going to cut it for many next-gen console owners. Furthermore, USB storage solutions, while affordable, might not be fast enough to keep up with the advanced tech of the new devices. We don’t know how it will work, but it seems likely that Microsoft will include a storage expansion slot like the ones you see on Android phones for the Xbox Series X.

Jacob started covering video games and technology in college as a hobby, but it quickly became clear to him that this was what he wanted to do for a living. He currently resides in New York writing for BGR. His previously published work can be found on TechHive, VentureBeat and Game Rant.