Line an 8-inch square pan with parchment, leaving overhang for easy lifting.
Combine chocolate chips, condensed milk, and butter in a large microwave-safe bowl.
Microwave in 30-second bursts, stirring after each, until smooth and glossy, 1½–2 minutes total.
Stir in vanilla and salt, then fold in the pecans until evenly distributed.
Spread the fudge into the pan and smooth the top; tap the pan to release air bubbles.
Chill until firm, 1–2 hours. Lift out, slice into small squares, and serve.