Matching RAM sticks is safest, but not mandatory.

Ideally, yes. Same model, same batch, same everything — that’s the gold standard for zero headaches.

The reason: RAM is tuned at the factory with specific timings, voltage, and frequency. Mixing two different sticks, even from the same brand, can force your motherboard to use the slowest common denominator or throw errors if the modules don’t play nice. You can sometimes get away with it, especially if both sticks share the same primary specs (DDR4-3200 CL16, for example), but it’s a gamble.

If you’re building from scratch, just buy a matched kit (two sticks in one package). If you’re upgrading and have to mix, check your motherboard’s QVL list and be prepared to run stability tests. Worst case, you’ll need to dial back speeds manually.

But for 99% of people: buy the same model. It’s cheap insurance against random crashes.