Yes, it's a USB port. Let's get that out of the way right off the bat, as if the big picture of a USB port on a router above wasn't enough to tip you off. In case you've never noticed, or thought to use it, if your router has a USB port on it there's a good chance you can actually use that router as a basic NAS.
That USB port turns your router into a basic NAS
That's great news if you're in the market for network storage solution, because it might turn out you already have all the parts you need to make it work.
If you connect a USB hard drive to your router, you can usually activate it as a shared network drive in the router's settings. Just be aware that not every router with a USB port lets you use it as network storage. In some cases, that port will only work as a mobile network backup solution. Allowing you to connect a fallback USB modem in case your landline goes down.
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It's also important that the port be a USB 3.0 port, which you can usually tell by the blue interior color of the port itself. If your router has an older USB 2.0 port, that's also only good for backup modems, which work fine with USB 2.0's 480Mbps limit.
The exact details of how to set up USB storage shares using your router can only be found in that specific router's manual. In some cases, even if your router doesn't support storage over USB out of the box, you might be able to install custom router firmware which adds this feature.
For casual file sharing, it's surprisingly good enough
Before I switched over to a mesh network solution with no USB storage features, I ran a hard drive connected to my router for years as a network share. Recently, I even dusted off one of my old routers with a USB drive for an isolated network project that I didn't want on my main LAN, and was again impressed by how well the drive performs.
It only really falls apart when lots of different clients are trying to read and write data to the drive, but then that's generally true for any hard drive based storage that's shared. If you're taking turns using the shared storage (e.g. backups overnight, playing media files in the day) then I dare say most people would be perfectly happy with this setup.
Why this threatens cheap NAS boxes the most
Jordan Gloor / How-To Geek
If you're looking at the cheapest, most entry-level NAS options on the market you're not getting much in the way of processing power or network speed anyway. So, depending on your use case, buying or building a cheap dedicated NAS might not actually net you any benefits compared to simply plugging a drive into your router.
Perhaps most importantly, you can just go ahead and test this today using any old USB drive. Even a flash drive, if you just want to see if it works or not. Even if a cheap dedicated NAS might be better on paper, if using your router's storage sharing function works well enough for you, why spend more?
The limitations you need to understand up front
The whole reason I advise you do a test with whatever you have first before going out and buying a big USB hard drive is that router storage shares have limitations. This is a very unsophisticated way to share a drive on the network. More importantly, you're usually limited to just one drive. In my experience, connecting a USB hub to the router does not let it share multiple drives, though perhaps your model is a fancy one that does have this ability.
Performance will be limited compared to even mid-range NAS devices, and you can't make use of features like RAID to protect your data or speed up transfers. Also, unless you have a very special router indeed, you can't run self-hosting apps either. It's just a USB drive that everyone can access over the LAN.
There's also the issue of privacy and security. Even basic NAS devices can offer you encryption and other ways to keep unwanted users out, but this only matters if you want to store sensitive data on the drive, and of course, you can encrypt individual files before uploading them yourself too.
When a real NAS still makes sense
If you need more than that, you still need a proper NAS. The second you need multiple drives, that's already case closed for the USB router method. The good news is that there are plenty of budget NAS solutions. You can use an old PC , build one using a Raspberry Pi , or get one of the many new NAS options that are targeting casual users.
