Momentum trading on Interactive Brokers: scanner setup for gappers

Interactive Brokers has a capable market scanner built into TWS, at no cost beyond the market data you already pay for. It is just not set up for small-cap momentum out of the box, and it says nothing about float. This guide sets it up for one job: finding the US small caps that are gapping and moving before the open.

Scalpel is independent and not affiliated with or endorsed by Interactive Brokers.

What a momentum scanner has to find

Small-cap momentum traders mostly look for the same five things, whatever course or book they learned from: a low price, a big move already under way, heavy volume against normal, a news reason, and a small supply of shares. The scanner can handle the first three directly. News and supply need a second look.

Set up the IBKR pre-market scanner in TWS

IBKR calls the full tool the Advanced Market Scanner (IBKR's guide). Mosaic also has a simpler scanner window, but the advanced one gives you every filter and the Max results field.

1. 01

   Open the Advanced Market Scanner

   In the Mosaic layout, open the New Window drop-down and choose Advanced Market Scanner. In the Classic layout it is Analytical Tools > Advanced Market Scanner; IBKR recommends opening it as a new window rather than a tab.

2. 02

   Choose the instrument and location

   Set the instrument to US stocks and the location to the major US exchanges. Leave OTC out: most OTC names are hard to trade fast and the scanner fills up with them.

3. 03

   Pick the scan parameter

   Choose Top % Gainers for your main gapper scan. IBKR defines it as the stocks whose last price shows the biggest percent gain over the previous night's close (scan definitions), which is exactly what a pre-market gap is.

4. 04

   Add the filters

   Add a price filter (above 1, below 20), a minimum percent change (10), and a minimum volume. Filter labels differ a little between TWS versions; type the field name into the filter search if you cannot see it. IBKR lets you stack several filters but sort by only one parameter. The table in the next section has values to start from.

5. 05

   Run it and set Auto Refresh

   Click Search, then tick Auto Refresh so the scan reruns on its own. Most scans return the top 50 stocks by default; change Max results if you want a shorter list.

6. 06

   Save it as a template

   Use the save icon next to Max results to save the scan as a template, then build your second and third scans (below) from it by changing only the scan parameter.

IBKR scanner settings for small-cap gappers

These are starting values, not magic numbers. Widen them on a slow morning and tighten them when everything is running.

A worked example: at 07:40 ET a fictional stock ABCD trades at $4.10, up 38% from yesterday's $2.97 close, on 1.2 million shares. It passes every filter above. WXYZ is up 14% at $31: it fails the price band and never shows, which is the point.

Which scan types to run

For momentum, a handful of IBKR's scan parameters matter. These are IBKR's own names and definitions:

Run Top % Gainers as the main window, with Hot Contracts by Volume and Halted beside it. Add Most Active after 09:30 when volume is real.

How the IBKR scanner behaves in the pre-market

This is where most "my scanner shows nothing" questions come from.

• Gainer and volume scans work pre-market. When we tested IBKR's scanner through the API at 06:11 ET, Top % Gainers, Hot Contracts by Volume, Most Active, Top Volume Rate and Halted all returned live pre-market rows, with the change measured against yesterday's close. TWS must be logged in; IBKR's extended session starts at 04:00 ET.
• Open-gap scans are empty until 09:30. Any scan measured to today's opening price, such as Top Close-to-Open % Gainers or the gap and since-open scans, returns nothing before the open because there is no opening price yet. That is not a broken scanner. Use Top % Gainers until 09:30.
• Relative volume starts low. Hot Contracts by Volume compares today's volume so far with a whole average day. At 07:30, a stock at 2x has already traded two normal days of volume before the open, which is huge.
• Rows and refresh. In TWS, most scans return 50 rows by default, and IBKR's guide says the data updates every 60 seconds. Through the API, IBKR caps each scan at 50 results and allows 10 scanner subscriptions at once (API docs); in our testing API scans refreshed about every 30 seconds. Either way, read the live price and tape on the stock itself.

Details checked against IBKR's documentation on October 15, 2026.

What IBKR's scanner cannot filter: float

Float is the number of shares free to trade: shares outstanding minus those held by insiders and other locked-up holders. It is the number small-cap traders ask about most, and it is the one IBKR does not give you cleanly.

• Through the API, the float filter is refused. When we asked IBKR's scanner for a float filter over the API, it answered with error 10360, "Scan filter floatSharesBelow is not allowed", and the float-ranked scan codes failed too. Any tool built on IBKR's API, Scalpel included, has no float filter from IBKR.
• IBKR does not offer a reliable free float field. Float figures come from fundamentals vendors, are often weeks out of date, and change the day a company sells new stock.
• Shares outstanding is the free stand-in. US companies report shares outstanding on the cover of their 10-K and 10-Q filings, free on SEC EDGAR (foreign issuers filing 20-Fs report it less often). The float is never bigger than shares outstanding, so a small number there is a sure low float. A big number can still hide a smaller float, but at least you know where you stand.

Before you trade a gapper, check the filings for a fresh S-3 shelf, 424B prospectus or ATM offering: a company that can sell stock into your move is a seller on every spike. Checking dilution walks through what to look for.

A pre-market scanning routine

1. 04:00 to 07:00 ET: let the list build. Log in to TWS early. Run Top % Gainers with the change floor at 5% and the volume floor low; early lists are short.
2. From 07:00 ET: tighten the filters. Raise the change floor to 10% and the volume floor to 100,000. The names left are the ones with real interest.
3. Check why each one is moving. Open the news for each row. No headline is a warning sign, not a reason to buy.
4. Check the supply. Look up shares outstanding and recent filings on EDGAR. Strike out names with a fresh offering or shelf.
5. Pick two or three. Put them in your Level 2 and time and sales windows, and mark the pre-market high and VWAP.
6. 09:30 ET: expect a reshuffle. Add a Top Close-to-Open % Gainers window, and watch Halted as the open brings volatility halts.

The complete setup for day trading on Interactive Brokers covers the data subscriptions, layout and order settings around this routine. For the trading style itself, see small-cap momentum trading on Interactive Brokers.

Where Scalpel fits

Scalpel runs on the same IBKR market scanner, over the TWS API, so there is no scanner service or extra data feed to pay for. What it adds is the merging and the second look, so the routine above happens on one panel (set up the IBKR scanner).

• Five scans merged into one list. Top gainers, 3 minute volume spikes, halted, hot by volume and gappers run side by side with the same filters, and Scalpel merges them into one list ranked by change. Out of the box it lists up to 30 US stocks between $0.10 and $100 that are up at least 10%, pre-market included. Gappers stays empty until 09:30 ET, as in TWS.
• Live numbers between refreshes. IBKR sends symbols only, about every 30 seconds; the price, change and relative volume on each row come from your own IBKR quotes, tick by tick.
• Shares out, not float. The SHS OUT column is shares outstanding from SEC filings, and Max shares out (M) caps it. Dilution, catalyst and borrow chips sit on each row.
• Three scans on top of the list. High of day momentum shows a listed stock breaking its high of day, pre-market included. Running up shows a stock up 2% in about a minute on a volume burst, with its own filters ($2 to $20, under 10M shares out by default). Setups marks patterns such as gap and go and the micro pullback with a letter chip (scan types).

07:42:15 ETPre-market

IBKR scanner 4LIVE

RANKSYMPRICECHG%VWAPINTELSQZRVOLSHS OUTSHORTMKT CAPVOLDESK

1TUVW3.62+26.1%Trial data 52m639.8x9.1M11% 2.2d$33.0M4.0M

2+1PQRS1.71+15.5%Hype 3h586.4x4.2M18% 3.4d$7.2M8.5M

3-1CDEF2.27+12.4%Selling 2hOffering 2h104.1x17.5M7% 1.3d$39.7M6.2M

4QRST6.05+11.0%Deal 1h342.2x21.4M4% 0.9d$129.5M610K

Pre-market scanning in Scalpel covers what each scan does before 09:30. Where TWS is the better choice: if you scan other markets, options or fundamentals, or want hundreds of rows, TWS's scanner is far broader. Scalpel scans US stocks for long momentum only.

Trading carries a significant risk of loss. Nothing here is financial advice.

Questions

Does the IBKR scanner work in the pre-market?

Yes. Top % Gainers, Hot Contracts by Volume, Most Active and Halted return pre-market rows, with change measured against yesterday's close. Scans measured to today's opening price stay empty until 09:30 ET.

Can I filter by float in the IBKR scanner?

Not through the API: IBKR refuses the float filter there, and it does not offer a reliable free float field. Shares outstanding from SEC filings is the free stand-in, since the float is never larger.

How many results does the IBKR scanner show?

Most TWS scans return the top 50 by default, adjustable in the Max results field. Through the API each scan is capped at 50 results, with up to 10 scanner subscriptions at once.

How often does the TWS scanner refresh?

IBKR's TWS guide says scanner data updates every 60 seconds with Auto Refresh on. API scanner subscriptions refreshed about every 30 seconds in our testing.

What are good IBKR scanner settings for gappers?

A common start is Top % Gainers on US stocks, price $1 to $20, up 10% or more, and at least 100,000 shares traded. Loosen the change and volume floors before 07:00 ET, when the list is thin.

Does the IBKR scanner cost extra?

No. The scanner is part of TWS. You need IBKR's real-time US stock data for live prices on the rows, which is a market data subscription you pay IBKR for.