Stats › Intraday and market microstructure › Extended hours
Before and after the bell
You can trade US stocks at three in the morning now. That's true, and it's the part everybody repeats. What gets left out is how much it costs and how few names are actually available.
This page is the measurement. The session definitions, the share of volume that trades outside the regular 09:30 to 16:00 window, the spreads and depth out there compared with core hours, and where the exchanges' filings to extend hours have actually got to as of August 2026.
I put it together because the gap between the headline and the numbers is unusually wide here. Extended hours is about 11% of daily volume. The true overnight window, 20:00 to 04:00, was 0.38% of share volume in a 2025 academic study. And the quoted spread out there ran up to 144% wider. Every one of those is sourced and dated at the bottom, including two exchange research desks and one peer reviewed style working paper that disagree less than you'd expect.
Extended hours trading is about 11% of total US daily equity volume, up from just over 5% in Q1 2019, and in January 2025 it was over 1.7bn shares a day. But the overnight window is tiny: Eaton, Shkilko and Werner measured 0.38% of share volume and 0.68% of trades from January to May 2024, and NYSE put 2025 to date at under 0.11% of shares. The cost difference is the point. For the 3,026 stocks with any overnight trading, quoted spreads averaged 63.92bp overnight against a regular hours effective spread of 29.76bp, and Nasdaq summarised retail effective spreads overnight as around 3 times regular hours with price impact about 6 times larger. Only 644 stocks trade more than $10,000 a day overnight, against more than 10,000 during core hours.
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Below this point there are 8 sections, 1 chart, 1 table and 7 named sources, roughly 2400 words of it. Every figure carries the source it came from and the date the data is from.
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