How to replace HDD with SSD in Apple Airport Time Capsule?

Just to let you know ... using a SSD, in replace of the HDD in a Time Capsule (TC), will not provide you with any performance benefits, and come at a much higher cost. Also, you didn't mention which exact model TC that you have.

Some advice:

• Don't use 2.5" HDDs. The TC was designed to mount a 3.5" HDD.
• Use "standard-performance" drives. Whether they spin at 5400 vs. 7200 should not matter. High performance drives will offer no real performance increase. Some suggested replacement drives would be the WD Blue series drives.
• The TC uses a SATA II 3GB controller.
• Do not use HDDs that use SMR.

With that said, you can find a number of article on the Internet, that will take you through the process of doing a HDD to HDD replacement. One can be found at the iFixIt site.

You may find the following helpful, as well: Upgrade & Partition TC internal hard disk… - Apple Community

What is the Model Number of the Time Capsule that you have?

If you are not sure......and your Time Capsule is "flat" like a small white pizza box......the Model number is usually on the bottom of the device embedded in the foam pad base. The model number starts with an "A" followed by 4 numbers.

If your Time Capsule is "tall" like an 8" tower, you have model number A1470.

Regardless of which Time Capsule that you might have, hopefully you are not thinking of replacing the hard drive without also replacing the Time Capsule power supply........correct? We ask because the power supply usually fails before the hard drive fails. The power supply in your Time Capsule is very likely overdue to fail.

... and it will be impossible to offer you any advice without you answering my questions about what exact SSD that you are planning on using with this TC ... and, Bob's question on what exact model is your TC?

Ok, that's certainly your call to make.

Do you already have the SSD? If so, what type is it and what type of connector does it currently have?