CPU-Z shows you without opening the case.

Yes, you can check for free RAM slots without even touching the side panel.

Download CPU-Z (free, tiny, no bloat). Open it, go to the SPD tab. It lists every slot on your motherboard. If you see “Slot #1” and “Slot #2” but only one has data, you’ve got a free slot. If both show data, you’re full and need to replace sticks, not add.

If you’re on a laptop, it’s trickier — some have soldered RAM you can’t see in CPU-Z. But for a desktop, this is instant. No screwdriver needed.

Physical check is still the most reliable, but CPU-Z gets you the answer without getting off your chair.