Core terms
Opening cross (opening auction)
The auction that sets a stock's official opening price by matching eligible orders at a single price at the start of regular trading. Nasdaq calls its version the Opening Cross.
Under Nasdaq Rule 4752 (as of 2026-10-05; SEC-published rule filings), Nasdaq publishes imbalance information from 9:25 a.m. ET and the Net Order Imbalance Indicator every second from 9:28 a.m. ET until the cross. The cross picks the price that executes the most shares, then the one that leaves the smallest unmatched imbalance, then further tie-breakers; the result is the Nasdaq Official Opening Price. Late limit-on-open orders, imbalance-only orders and continuous-book limit orders can change the book until the cross runs.
The opening print can differ from the last premarket trade in either direction. In the FennEdge Gapper HOD study, 53.1% of stocks that gapped up 20% or more printed their 04:00–20:00 high in premarket, and 21 of 671 (3.1%) printed it in the 09:30 minute (2026-07-01 to 2026-10-02; FennEdge archive; as of 2026-10-02).
NYSE and NYSE American
NYSE runs a Core Open Auction facilitated by a Designated Market Maker (Rule 7.35A); NYSE American auctions run under its Rule 7.35E (as of 2026-10-05). Message names, fields and timing differ by listing exchange.
What traders should verify
Check the listing exchange before reading any imbalance feed, and write in the plan whether a premarket position is closed before the open or held into the cross. A stop held into the open meets the opening print, wherever it lands.
Do not conflate
Imbalance messages and indicative prices describe the auction book at one moment; orders arrive and leave until the cross, so a large imbalance does not fix the opening price. The measured figures above describe when the day's high printed, not how the opening print compared with premarket trading.
Primary source
Primary sourceNasdaq Rule 4752, SEC Release No. 34-91096, Exhibit 5