While you can open up the Steam Deck without voiding your warranty, you need to take a few precautions before doing so.
If you bought the entry-level Steam Deck and want to replace the internal SSD storage, or if something broke with your device and you want to fix it yourself, you'll need to open up the Steam Deck. But should you?
Will opening up the Steam Deck void the warranty?
The short answer is: no. The long answer? It's a little complicated.
Thankfully, Valve designed the Steam Deck to make it easy for owners to open it up and replace things on their own. In a welcome move, Valve even collaborated with the excellent 'how to' website iFixit to offer replacement parts and detailed repair guides — such as this complete teardown. iFixit have rated many products over the years for their repairability and give the Steam Deck a good "seven out of ten" rating.
However, the Steam Deck remains an electronic device with a Lithium-battery, and Valve stated clearly in their teardown guide that you should not open it up if you are unsure what to do. This is why they only recently announced their own repair centres.
But take it from the community and us: Opening up the Steam Deck to change an SSD (or even replace the joysticks with hall-sensing ones from GuliKit) is not very complicated and can be done with the right set of screwdrivers. You should be safe if you don't poke around the battery.
If you decide to give some DIY Steam Deck work a go, beware of one thing: remove the microSD card before opening it up, or you risk snapping it in half. Reddit knows a thing or two about breaking the microSD cards.