Can I be 100% certain that a PCIe x4 card will fit in a PCIe x16 slot?

can i put pcie x4 in x16 slot   Dan can you use ddr5 in ddr4 slot

There's been talk that some PCIe slots on new motherboards will (The support may only be extended to ordinary PCIe x16 expansion slots

PCIe cards can always operate in PCIe slots with the same or more lanes than the card For example, an x8 card can operate in a slot with x8, x16, or x32 lanes  PCIe x4 devices are compatible with larger PCIe slots such as x8 and x16, and can be installed in these slots as well However, the bandwidth of the device is

cat slot 1 analysis 2023 Gen isn't upgradeable on PCIe slots speedstep  PCIE cards are backwards compatible with the and the slots, but you won't be able to enjoy the full extent of your new PCIE card