Adding memory to Time Capsule

LaPastenague makes a good point regarding the age of the Time Capsule. While you can usually connect a USB drive to the port on the Time Capsule, I would not advise doing this if you are looking for a long term storage or back up solution.

In addition, as I mentioned previously, the USB port on the Time Capsule is an old (and slow) USB 2.0 design that will result in file transfers and backups taking twice as long compared to moving files to the Time Capsule hard drive.

Is there some special formatting that I need to do?

Yes, the USB drive needs to be formatted in Mac OS Extended (Journaled), also known as HFS+. To find out how your USB drive is currently formatted, connect it directly to your Mac, and the hard drive icon should appear on the Mac's desktop. Right-Click on the hard drive icon, and then click on Get Info. Look for Format to see how the hard drive is currently formatted.

Once the hard drive is formatted correctly to work with the Time Capsule, you can connect it to the USB port on the Time Capsule.

Note 1......the USB port on the Time Capsule is a very old, low powered design, so you may find that you need to use a powered USB hub connected to the Time Capsule with the hard drive connected to the powered hub.

Note 2.....the USB port on the Time Capsule is an old USB 2.0 design. Chances are, your new hard drive is a USB 3.0 design. USB 3.0 is supposed to be backwards compatible with USB 2.0, but this is not always the case.

Note 3.....the hard drive connected to the Time Capsule will act like a separate drive. You will not be able to combine the 1 TB Time Capsule with the new hard drive and have the two drives act as one large hard drive.

The last of the 1TB Time Capsule models is Gen3 A1355 which ceased production in mid 2011 with A1409 Gen4.

That means your time capsule is at least 10 years old.. and it could be a few more adding on earlier slower models.

It is really not a great plan using it for backups..

Plug the hard disk directly into the Mac and use it that way will work far better.

If it is a 5TB portable drive that is especially important because it is an SMR drive.