Preheat the oven to 325°F. Line two baking sheets with parchment paper.
In a small bowl, whisk flour and cocoa powder. Stir cacao nibs and salt together.
1 cup AP flour, ⅔ cup unsweetened cocoa powder, ¼ cup cacao nibs, ¼ teaspoon Fine sea salt
Using a stand mixer with a paddle attachment (or with a hand mixer), cream the butter and sugar until smooth and creamy, about 1 minute. Mix in the vanilla.
6 ounces unsalted butter, ½ cup granulated sugar, 1 teaspoon pure vanilla extract
Add the flour-cocoa mixture in two additions on low speed, mixing just until the flour is no longer visible. Scrape the bowl as needed.
Add the cacao nibs and salt. Mix on low just until combined.
Turn out the dough onto wax paper or parchment and roll into a 2" round log about 6 to 7 inches long. Wrap tightly and chill 1 to 2 hours. Refrigerate up to 1 week or freeze up to 2 months.
Slice into 1/4-inch rounds and place 1 inch apart on the baking sheets.
Bake for 15 minutes, or until the cookies look set and the edges feel firm. Transfer cookies to a cooling rack, then store in an airtight container for 1 week.