Gap Scanner

Premarket Gap Scanner: Gappers From First Print to the Bell

A premarket gap is a moving number. The gap at 7:00 a.m. is rarely the gap at 9:30, so the scan has to keep reading the latest print.

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Watch the premarket gap change

Before the open, Gap (%) and Gap ($) use the latest premarket print against yesterday’s close, so the list re-ranks as trades come in. Three more pieces show whether the gap is growing or shrinking:

Example numbers, not a real trade

One premarket gap, four readings
One premarket gap, four readings. Example numbers, not a real trade.

Only want gap ups? Set the Gap (%) minimum above zero. Gap downs: set a maximum below zero. For the wider premarket picture, see the premarket scanner.

Premarket hours, hour by hour

Premarket isn’t one block of time. It acts different depending on the clock, and a scan that ignores that will show you a lot of noise.

  • 4:00 to 7:00 a.m. ET. Very thin. A few hundred shares can push a stock 15%. Good for spotting news early, not for trusting the price.
  • 7:00 to 8:30. Volume starts to show up, especially on earnings names. Gaps start to mean something.
  • 8:30 to 9:30. Economic numbers hit at 8:30, and the gap list can reshuffle in a minute. This is when most traders build the final watchlist.

A simple way to fight the thin-print problem is a volume floor that rises with the clock. Some traders run 25,000 shares before 7:00, 100,000 by 8:00 and 250,000 by 9:00. Trade Ideas lets you keep separate saved scans for each, so you just switch windows as the morning goes.

Trader tip

Example, made-up numbers. A $30 biotech prints $33 at 5:10 a.m. on 4,000 shares, a 10% gap. By 7:30 it’s back to $31.20 on 90,000 shares, so the gap shrank to 4%. At 8:40 a second headline hits and it runs to $32.80. The premarket high alert fires there because it topped the earlier 7:00 high. Position in premarket range reads 100. If you had trusted the 5:10 print, you would have been chasing a number that was gone two hours later.

Also watch the distance below the premarket high right before the bell. A stock sitting 3 cents under its high at 9:29 has buyers leaning on it. One sitting 80 cents under has already given some back, and that changes the open quite a bit.

Last thing: premarket highs and lows make handy lines for the regular session. A lot of opening moves start right at them, which is why the alert exists in the first place.

Key point

A note on news timing. Many companies report earnings between 6:00 and 8:00 a.m. ET, and the gap can flip in seconds when the numbers cross the wire. If a name on your list goes quiet right before its report, that’s why. Mark the report times on your watchlist so a sudden 12% swing at 7:01 doesn’t surprise you. Then let the volume floor decide whether the new gap is worth your attention or just early noise.

Try it on today’s market.

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Premarket gap scanner questions

Premarket gaps, answered plainly.

When does premarket gap data start?

As soon as a stock prints in the premarket. Early prints are often thin, so many traders wait for real volume before trusting the gap.

Is a premarket gap up scanner a different tool?

No. It is this scan with the Gap (%) minimum set above zero, so we keep it on one page.

Why did my premarket gapper shrink by the open?

The gap is measured against the latest print. If sellers show up at 9:00, the gap gets smaller before the bell.

Why use different volume floors at different times?

Early premarket volume is tiny. A rising floor keeps 5 a.m. prints of a few hundred shares from filling your list with gaps that vanish by 8.

Alerts and filters to look at

Results are not typical. Trading involves risk; most day traders lose money. Past and simulated results don't guarantee future results.

Past results, including backtests, don't guarantee future results.

See which premarket gaps are building.

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