Midpoint Peg

What is midpoint pegging (Mid) — the dark pool

This is a special mode for limit orders. Your order does not appear in the visible order book and does NOT trade against ordinary orders. Instead it waits "in the dark" and is matched only with other midpoint (Mid) orders — at the live midpoint of the spread (halfway between the best buy and the best sell). Trades happen in queue order (first in, first served). It's like a hidden "dark pool": you can't be seen in the book, and until another Mid order crosses with yours, you simply wait.