Gap Scanner: Find Premarket and Open Gaps
Learn what a gap scanner detects before and after the open, which filters matter, and how to paper-track gap candidates without treating them as trades.
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Gap scanner: A gap scanner compares a selected session price with a reference close. Confirm adjustment and session conventions, then distinguish a displayed premarket indication from an executable order price.
What a Gap Scanner Finds
A gap scanner finds stocks trading above or below a reference price, commonly the prior session's close. It can scan premarket quotes, the opening print, or later intraday changes. A gap is a market condition worth researching, not a signal to buy, sell, or assume a gap will fill.
This guide covers scanning. For setup education, read gap trading strategies; for wider market filters, use the stock scanner guide.
Choose a Clear Reference and Time Window
Most scanners calculate a percentage difference from the prior close. During premarket, quotes may be thin and move quickly; at the open, spreads and volatility can change again. Record whether the figure is premarket, opening, or regular-session data before comparing candidates.
Be wary of a large percentage move in an illiquid stock. A small number of shares can create a striking gap while offering poor price discovery and difficult exits.
Filters That Support Research
- Gap percentage: Use a range that matches your research process, rather than chasing the largest number.
- News source: Separate verified filings, company news, and unverified commentary.
- Liquidity and volume: Check current activity against normal activity with relative volume.
- Price and spread: Establish whether a hypothetical trade could be priced realistically.
- Market context: Index and sector moves can change how an individual gap behaves.
The terms gap trading and gap fill describe common ideas, not forecasts. A gap can hold, fade, extend, or remain open.
Paper-Track a Scanner List
Before the open, choose a small maximum number of names and document why each made the list. After the open, note whether volume confirms interest, whether price holds a key level, and what invalidates the observation. If you model a position, use a defined entry, stop, target condition, realistic slippage, and conservative size.
Use a consistent paper trading guide process for every candidate. Do not replace rules after the result is known. That protects the journal from hindsight bias.
Tradewink's signals provide research context for informational purposes. You can create an account at /sign-up to paper-track ideas; Tradewink does not custody funds, and public plans are paper trading only. Public plans do not include live order submission.
Put the setup on a watchlist first
Use the rules in this guide to evaluate a signal’s entry, stop, target, and reasoning before deciding what, if anything, to do.
Public subscriptions are paper-only; separately approved private beta accounts may submit live broker orders.
Gap scanner: practical checks
Confirm the reference close, corporate-action adjustment and eligible trading session. Separate a price indication from a tradable quote, and test both continuation and reversal cases with realistic spread assumptions.
Read the SEC order types bulletin for the underlying definitions and limits. For a next step, use Stock Scanner: Filters, Coverage and Data Limits and Gap Trading Strategies: Gap Fills, Gap-and-Go & Risk.
Frequently Asked Questions
Is premarket volume as reliable as regular-session volume?
Not necessarily. Premarket participation is usually smaller and can be concentrated. Treat it as context that must be reassessed at the regular open.
Should a scanner include every gapping stock?
No. A deliberately narrow universe and clear liquidity criteria make review more manageable and reduce noise.
Can a gap scanner tell me the best entry?
No. It identifies price differences. Entry and risk decisions require a separate plan, live market conditions, and an understanding of execution limits.
Trading involves risk, including loss of capital. Tradewink is not an investment adviser, and this article is educational rather than personalized investment advice.
Read next
Keep learning with a related guide before putting an idea on your watchlist.
Stock Scanner: Filters, Coverage and Data Limits
Stock scanners explained: how real-time filters work, best settings for swing and day trading, and how to avoid false signals in volatile markets.
Gap Trading Strategies: Gap Fills, Gap-and-Go & Risk
Learn gap types, gap-fill and gap-and-go setups, entry assumptions, volume filters and risk checks. Review opening gaps with a paper-first workflow.
Paper Trading App Workflow: Review Stock Signals
Use a paper trading app workflow to review stock signals, record entry, stop, target, and rationale, then revisit decisions without a broker connection.
Try AI signals on your watchlist
Send yourself a signal preview, then add tickers to see ranked entries, exits, and risk notes in Tradewink.
Sources cited in this guide
- SEC order types bulletin (investor.gov)
Tradewink builds explainable market research for self-directed traders. Build a watchlist, inspect signal reasoning and risk context, and paper-track ideas before you decide. Public subscriptions are paper-only; separately approved private beta accounts may submit live broker orders.
How this guide is reviewed
Tradewink reviews educational content against its documented market-data sources, risk controls, and product methodology. See our data sources and evaluation methodology for the evidence and limitations behind the platform, and our editorial standards for how guides are sourced, dated, and corrected.