Most used flip-flop in the industry?

If I tell you from a practical digital circuit design perspective, D flip-flops are by far the most commonly used among all types—D, T, JK, and SR.

The reason is simple: they’re straightforward and predictable. Whatever data you give at the D input gets transferred to the output Q on the clock edge, which makes them really easy to understand and implement, especially when you're dealing with things like counters, registers, or finite state machines.

On the other hand, flip-flops like JK and SR might seem more functional, but they come with added complications. For example, SR flip-flops can go into an invalid state if both inputs are high, and JK flip-flops—though they solve that issue—toggle in a way that can be tricky to manage in complex synchronous circuits.

T flip-flops are mostly used in counters, but even they are usually made using D flip-flops and some extra logic. Also, when it comes to tools like FPGA or ASIC design software, everything is optimized around D flip-flops because they’re easier to synthesize and analyze for timing.

Even if you need the features of other flip-flops, you can build them using D flip-flops and a bit of logic, which is why D flip-flops remain the go-to choice in real-world digital design.