Core terms
Net Order Imbalance Indicator (NOII)
Nasdaq's auction message showing paired shares, imbalance size and side, and the near and far indicative clearing prices. Before the open it is disseminated every second from 9:28 a.m. ET until the cross.
Under Nasdaq Rule 4752 the opening process publishes two stages of messages (as of 2026-10-05). From 9:25 a.m. ET an Early Order Imbalance Indicator appears every 10 seconds with the current reference price, paired shares, and imbalance size and side. From 9:28 a.m. ET the NOII appears every second until the cross and adds the near and far indicative clearing prices.
Paired shares would match at the current reference price; the imbalance is the unmatched remainder and its side. Both describe the auction book at that second. Market-on-open and limit-on-open orders cannot be cancelled or modified from 9:25, but imbalance-only orders can be entered until the cross runs and continuous-book limit orders can still be cancelled, so the imbalance can shrink or flip between messages.
NYSE and NYSE American publish their own auction imbalance information under their own rules and timing.
What traders should verify
Record the last NOII before your decision (imbalance, side, near price) and the actual opening print, and compare them over many sessions before treating the message as informative.
Do not conflate
The NOII shows the auction book, not intent or the final print; a large buy imbalance seconds before 09:30 can be followed by a lower open. Third-party screens may relabel the fields.
Primary source
Primary sourceNasdaq Rule 4752(d), SEC Release No. 34-91096, Exhibit 5