Reading the session
Gap up, gap down, and premarket change: which price are you comparing?
Learn how gap up and gap down are calculated, how opening gaps differ from premarket changes, and why the reference price and timestamp matter.
Articles
Related explainers
Data study
What Time Do Small-Cap Gappers Hit Their High of Day?
A look at 671 US stock gap-ups of 20% or more from July 1 to October 2, 2026: when the 4:00 a.m.–8:00 p.m. ET high printed, split by gap size, price and how the day ended.
Research process
A stock suddenly moves: how do you establish what happened?
Research why a stock moved using company announcements, SEC filings, and a source-linked timeline. Separate confirmed events from explanations and unknowns.
Market status
What is a trading halt—and why has the stock stopped moving?
Learn what a stock trading halt means, how to check official halt codes and resumption times, and how to distinguish a halt from inactive or delayed data.
Market structure
LU and LD explained: from LULD price bands to trading pauses
Learn how limit up and limit down work in U.S. stocks: moving LULD bands, the 15-second limit state, reopening, and differences from SSR and news halts.
Retrospective data built after the session from stored records, with links to the original sources. Not real-time, not investment advice and not a recommendation to buy or sell any security.