PSpice and LTspice are native to Windows. If you are on Linux or macOS, or if you prefer open-source software, Ngspice is the engine of choice.

If you specifically need to run legacy files (.cir, .dat), try these:

You do not need to spend $5,000 to simulate circuits professionally. gives you the official Cadence interface at zero cost, while LTspice gives you unlimited freedom.