Gap Trading Strategies: Gap-and-Go and Gap Fill

A US stock opening above or below the previous regular-session close does not tell you whether it will continue or fill. It establishes an opening condition. A gap-and-go rule tests continuation after the open; a gap-fill rule tests movement back toward a defined pre-gap reference; an opening-range rule delays classification until a completed interval provides a high and low.

The useful task is not to guess which story sounds persuasive. It is to define the chart, session, gap, opening range, confirmation, failure, expiry, execution assumptions, and outcome before future candles are visible.

This page focuses narrowly on US-listed stock strategies around the regular-session open. For objective gap definitions, close-to-open versus full-range measurement, fill horizons, corporate-action checks, and cross-market data controls, first use the price-gap reading and measurement guide. For stock-versus-Forex overnight and weekend gaps, use the separate Stocks and Forex Gap Guide.

Educational note: Opening-gap trading involves volatility, uncertain execution, and potentially large slippage. Historical observations do not guarantee an executable price or future outcome.

Key Takeaways

The official regular-session open is an auction or opening-cross result, not simply the last visible pre-market trade.
Gap-and-go, gap fill, and opening-range breakout are separate hypotheses with different confirmation times.
A gap direction is known at the open; continuation or fill is known only after a predeclared event occurs.
Five-minute, 15-minute, and 30-minute opening ranges produce different samples.
Relative volume, catalyst type, pre-market behavior, market context, and float are features—not proof.
Partial fill, full fill, extension, failure, and expiry need separate labels.
Existing Bing demand confirms this page should remain the US-stock opening-strategy owner rather than becoming another general gap-definition article.

Which Gap Guide Should You Use?

Question	ChartMini owner
How is a gap objectively defined and measured?	Gap Reading, Measurement, and Fill Verification
How do stock and Forex overnight/weekend gaps differ?	Stocks and Forex Gap Guide
What happens in pre-market and after-hours trading?	Pre-Market and After-Hours Trading
What are the official US regular-session hours and holidays?	US Stock Market Hours Guide
How should catalyst and news reactions be recorded?	How to Trade the News
How should volume be measured rather than narrated?	How to Read Trading Volume
How do market, limit, stop, and stop-limit orders differ?	Order Types Explained
How can breakout and fakeout rules be practiced?	Breakout Trading Practice
How are US-stock Gap-and-Go, Gap Fill, and Opening Range rules compared?	This page

Why the Official Open Matters

US listed stocks can trade before 9:30 a.m. Eastern Time, but the regular-session opening price is produced through exchange-specific opening processes.

NYSE describes its Opening Auction as a price-discovery process that aggregates liquidity at the start of the trading day. Nasdaq's Opening Cross similarly matches eligible interest at a single opening price. These mechanisms mean:

the official open can differ from the last pre-market trade;
opening orders and imbalances can affect the first regular-session print;
a symbol can open later than 9:30 a.m. because of an auction, halt, or operational event;
the first chart bar may combine auction and continuous-market activity depending on the feed;
an opening-gap strategy should record which open and which data source it uses.

Do not assume that a pre-market quote is the final opening price.

Freeze the Chart and Session Identity

Record these fields before selecting any opening-gap candidate:

Field	Example record
Symbol	US-listed common stock
Primary listing venue	NYSE or Nasdaq
Data provider	Named provider
Price basis	Trades, bid, ask, midpoint, or consolidated bars
Previous-session close	Official regular-session close
Opening price	Official/opening bar reference from the selected feed
Extended hours	Included or excluded
Regular session	9:30 a.m.–4:00 p.m. ET unless a special schedule applies
Timezone	Eastern Time or explicitly converted timezone
Corporate actions	Split/dividend adjustment method
Bar interval	One-minute, five-minute, 15-minute, or another frozen interval
Candle status	Completed bars only

A stock split, symbol change, bad print, missing bar, or different adjustment method can create a false historical gap. Verify the data before assigning a strategy label.

Define the Opening Gap

Let:

C_prev = previous official regular-session close;
O_today = selected official/opening price for the current regular session.

Then:

gap amount = O_today - C_prev

gap percentage = (O_today - C_prev) / C_prev × 100

Positive values are gap-ups; negative values are gap-downs.

For cross-symbol comparison, also record a volatility-normalized version:

normalized gap = |O_today - C_prev| / volatility unit

The volatility unit can be ATR, prior-session range, or another measure calculated only from data available before the open.

This page does not redefine full-range gaps, partial gaps, or fill horizons. Those belong to the dedicated gap measurement owner.

Define the Strategy Universe

A rule tested on highly liquid large-cap stocks is not automatically valid for thin low-float stocks, ETFs, ADRs, newly listed securities, or halted names.

Record universe filters such as:

security type;
primary exchange;
minimum prior close;
minimum median dollar volume;
minimum or maximum market capitalization;
float range, if reliable data exists;
short-sale eligibility and locate assumptions;
earnings or non-earnings status;
exclusion of IPOs, mergers, bankruptcies, or corporate-action dates;
exclusion of symbols under trading halt or special opening condition.

Universe selection must be frozen before outcomes are reviewed.

Separate Gap Direction From Strategy Direction

A gap-up can produce multiple valid hypotheses:

bullish continuation;
bearish fade toward the prior close;
range/no-trade;
early continuation followed by later fill;
early fill followed by recovery;
unresolved behavior within the observation window.

A gap-down has the mirror possibilities.

Do not label every gap-up as a long setup or every gap-down as a short setup. First record the opening condition. Then wait for the strategy-specific confirmation event.

Define the Opening Range

An opening range is the high and low formed during a predefined interval after the regular-session open.

Let:

OR_high(t) = highest price during the selected opening-range duration t;
OR_low(t) = lowest price during the selected opening-range duration t.

Common versions include:

first completed one-minute bar;
first five minutes;
first 15 minutes;
first 30 minutes;
first hour;
first n completed bars;
event-based range ending after an auction or halt condition resolves.

There is no universal best duration. A five-minute range confirms earlier but is more sensitive to initial volatility. A 30-minute range confirms later and can exclude much of the first move.

Record the duration with every result. Do not use five minutes for successful examples and 30 minutes for failed examples.

Handle Delayed Opens and Halts

The clock can read 9:30 a.m. while a particular stock has not opened.

Possible cases:

primary-market opening auction is delayed;
volatility halt carries into the session;
news-pending halt delays the first trade;
IPO or new listing uses a separate price-discovery process;
data feed displays quotes before the first eligible trade;
Limit Up-Limit Down conditions interrupt continuous trading.

Choose a policy:

exclude delayed openings;
define the opening range from the symbol's first official trade rather than 9:30;
create a separate delayed-open sample;
require a minimum number of completed continuous-market bars after the open.

Mixing normal openings and delayed openings without labels can distort the results.

Strategy 1: Gap-and-Go Continuation Hypothesis

A Gap-and-Go hypothesis tests whether price is accepted in the gap direction after the regular-session open and continues away from the previous close.

The minimum components are:

a qualifying gap;
a completed opening range;
a gap-direction confirmation rule;
an invalidation rule;
an expiry window;
a defined continuation outcome.

For a gap-up, continuation is upward. For a gap-down, continuation is downward.

Gap-and-Go Rule A: Opening-Range Break

For a gap-up, confirm when a completed bar trades or closes above OR_high according to the selected version.

For a gap-down, confirm below OR_low.

Separate:

intrabar break;
completed close beyond the range;
close beyond a fixed buffer;
break with a minimum extension;
break followed by a second confirming close.

These are not interchangeable.

Gap-and-Go Rule B: Open-Hold Then Break

Require price to avoid a predefined gap-rejection boundary before the opening-range break.

Possible hold references:

official open;
opening auction price;
pre-market high or low;
midpoint between the prior close and the open;
previous-session high or low;
a frozen opening-range midpoint.

Define whether a wick, body, or close must hold the reference.

Gap-and-Go Rule C: Break and Retest

Require:

opening-range break in the gap direction;
return to a predeclared range-edge band;
no invalidation before the retest completes;
a completed hold or rejection event;
renewed movement in the gap direction.

Not every continuation move retests. This version creates a smaller and later sample.

Gap-and-Go Rule D: Acceptance Above or Below the Open

Define acceptance through variables such as:

number of completed closes in the gap direction from the open;
percentage of opening-range body above or below the open;
time spent beyond the open;
maximum penetration against the gap;
failure to return to a partial-fill reference within n bars.

Acceptance is a rule, not a story about buyer or seller control.

Gap-and-Go Rule E: Relative-Strength or Relative-Weakness Filter

Compare the stock's return with a frozen benchmark over the same interval.

Example:

relative return = stock return - benchmark return

Record:

benchmark symbol;
start and end timestamps;
whether beta or sector adjustment is used;
threshold selected before testing.

Relative strength can be a feature, but it does not identify institutional activity.

Strategy 2: Gap-Fill Mean-Reversion Hypothesis

A Gap Fill hypothesis tests whether price moves from the opening area toward a predefined pre-gap reference.

Possible fill references include:

25% of the close-to-open gap;
50% of the gap;
75% of the gap;
previous official close;
previous-session high or low for a full-range definition;
a previously frozen support or resistance zone.

Use the gap measurement guide for exact partial/full-fill conventions.

Gap-Fill Rule A: Opening-Range Reversal

For a gap-up, confirm when price breaks or closes below OR_low under the chosen version.

For a gap-down, confirm above OR_high.

This is later than fading immediately at the open and avoids assuming the open itself is the reversal point.

Gap-Fill Rule B: Failure to Hold the Official Open

Require a completed close back through the official opening price, possibly with a buffer.

For a gap-up:

close < O_today - buffer

For a gap-down:

close > O_today + buffer

This rule does not guarantee a full fill. It merely confirms rejection of the opening price under the chosen specification.

Gap-Fill Rule C: Partial-Fill Confirmation

Confirm only after price reaches a predeclared fraction of the gap.

This avoids entering on a small fade but confirms later. Keep the confirmation threshold separate from the final outcome threshold.

For example:

confirmation at 25% fill;
first objective at 50% fill;
full-fill outcome at the prior close.

Gap-Fill Rule D: Failed Gap-and-Go

First require a valid continuation attempt, then define failure:

opening-range break occurs;
extension fails to reach a minimum threshold;
price returns inside the opening range within a fixed window;
price closes through the opposite range edge or open reference.

This is a different sample from an immediate gap fade.

Gap-Fill Rule E: Failed Retest of the Open or Range Edge

Require price to move against the gap, retest a predefined opening reference, and fail to reclaim it.

Record:

reference price;
retest-band width;
maximum penetration;
confirming close rule;
expiry window.

Strategy 3: Opening-Range Breakout Without a Gap Bias

Some days gap but do not justify a directional gap hypothesis. An opening-range breakout can be tested without assuming continuation or fill.

Classify the first confirmed range break as:

gap-direction break;
fill-direction break;
both sides broken;
no break before expiry;
ambiguous because both thresholds occur in one OHLC bar.

This provides a neutral benchmark for comparing Gap-and-Go and Gap Fill rules.

The separate Breakout Trading Practice page owns generic breakout, fakeout, and retest drills. Here the range is specifically tied to a US-stock opening gap.

Define Catalyst Categories Before Testing

A catalyst can influence the distribution, but retrospective headlines are easy to overfit.

Possible categories:

earnings and guidance;
merger or acquisition announcement;
regulatory or clinical decision;
financing, offering, or dilution;
analyst rating or price-target change;
management change;
litigation or investigation;
macro or sector event;
sympathy move;
no verified material catalyst;
multiple catalysts;
unknown at the decision timestamp.

Record:

source publication time;
whether the information was publicly available before the open;
category assigned without reading the later price outcome;
whether the announcement occurred during pre-market, after-hours, or regular hours.

Do not use “strong catalyst” as an undefined filter.

Pre-Market Structure Is a Feature Set

Possible pre-market variables include:

pre-market high and low;
last pre-market trade;
pre-market range;
pre-market return from the prior close;
volume during a fixed pre-market window;
number of prints or bars;
distance from the pre-market high at the official open;
final pre-market trend or slope;
spread, if reliable bid/ask data is available.

FINRA warns that extended-hours markets can have lower liquidity, higher volatility, wider spreads, changing prices, and unlinked venues. Therefore:

a provider may not represent all venues;
raw pre-market volume may not be comparable across feeds;
the final pre-market price may be less representative than the opening auction;
market orders or unavailable order types can create execution differences;
a visually smooth pre-market chart can hide sparse trading.

Use pre-market features as recorded inputs, not as proof that a gap will continue.

Volume Must Be Versioned

“High volume” is not a reproducible rule.

Possible versions:

Pre-market relative volume

premarket RVOL = current premarket volume / median premarket volume for comparable days

Define the comparison window and session length.

Opening-bar relative volume

opening RVOL = current opening-bar volume / median volume for the same clock interval

Comparing the first five minutes with full-day average volume is not equivalent.

Cumulative opening volume

Compare cumulative volume from the open through minute t with the same interval over a frozen lookback.

Dollar volume

dollar volume = price × share volume

This may improve comparability across stocks with different prices, but still does not measure liquidity perfectly.

Volume does not identify the participant, establish conviction, or guarantee continuation. It is one feature to test.

Gap Size Needs Context

A fixed 3%, 5%, or 10% threshold can behave differently across stocks and regimes.

Record multiple versions:

absolute dollars;
percentage of prior close;
percentage of prior-session range;
ATR-normalized gap;
standard-deviation-normalized gap;
gap relative to recent overnight moves.

Possible buckets:

small;
medium;
large;
extreme;

The bucket boundaries must be defined before evaluation. Do not call a gap “overextended” without a stated normalization method.

Market and Sector Context Are Separate Features

Record the same-timestamp behavior of:

broad-market ETF;
sector ETF;
industry peers;
futures or index reference available before the open;
volatility index, if relevant.

Possible features:

aligned market gap;
stock-specific gap against a flat market;
stock gap opposite the market;
relative gap size;
sector confirmation or divergence.

Do not assume a market-aligned gap must continue or an isolated gap must fill. Test each category.

Full-Range and Partial Gaps Have Different Geometry

A close-to-open gap can exist while the current open remains inside the prior day's range. A full-range gap requires the current range to begin beyond the prior-session high or low under the chosen definition.

Record:

previous high;
previous low;
previous close;
current open;
distance from the prior range;
whether the open is inside or outside the prior range;
whether later opening-range bars enter the prior range.

Do not state that one class is universally stronger. Compare it in the selected dataset.

Define Confirmation, Failure, and Expiry Separately

Gap-and-Go candidate failure

Possible failure events:

close through the opposite opening-range edge;
close through the official open against the gap;
predefined partial-fill threshold reached before continuation;
full gap fill before continuation;
no confirmation before expiry.

Confirmed Gap-and-Go failure

Possible events:

price returns inside the range within n bars;
price closes through the open;
adverse threshold reached before continuation objective;
gap fully fills before the chosen extension threshold;
halt or data ambiguity prevents reliable evaluation.

Gap-Fill candidate failure

Possible events:

gap-direction range break occurs first;
price extends a specified distance away from the prior close;
no partial-fill confirmation before expiry;
opening structure remains range-bound.

Confirmed Gap-Fill failure

Possible events:

price reclaims the open or range edge;
continuation threshold occurs before the fill objective;
price never reaches the selected fill reference before the time horizon;
same-bar event order is ambiguous.

Expiry

Possible expiry windows:

first 30 minutes;
first hour;
noon ET;
regular-session close;
fixed number of bars after confirmation;
multi-day horizon for a separately labeled test.

Same-day strategy results should not be combined with eventual multi-week fills.

OHLC Bars Can Hide Event Order

Suppose one five-minute bar has:

a high above the Gap-and-Go confirmation threshold;
a low below the Gap-Fill confirmation threshold;
a close between them.

OHLC data does not reveal which threshold occurred first.

Choose one policy:

inspect one-minute or tick data available in the historical dataset;
use conservative ordering;
exclude the observation;
label it ambiguous;
report both possible outcomes.

Never choose the favorable sequence after seeing the bar.

Order Types and Opening Execution Risk

An opening-gap strategy is highly sensitive to execution assumptions.

Record:

market, limit, stop, stop-limit, or on-open order;
trigger price;
assumed fill rule;
bid/ask spread;
slippage;
partial-fill policy;
short-locate requirement;
borrowing fee assumptions;
commissions and regulatory fees;
whether orders can execute during extended hours;
behavior during halts or Limit Up-Limit Down states.

A stop order becomes a market order after triggering and can execute at a materially different price during a fast move. A limit order controls price but can remain unfilled. Review the Order Types Guide before converting chart thresholds into simulated trades.

Define Outcome Measures Before Testing

Directional extension

Measure movement in the gap direction from confirmation.

Fill fraction

fill fraction = distance moved toward prior close / original close-to-open gap

Cap or separately label values above 100%.

Maximum favorable excursion

Record the largest favorable movement before failure or expiry.

Maximum adverse excursion

Record the largest adverse movement over the same event window.

Fixed-horizon return

Measure return after a frozen number of minutes or bars from confirmation.

Threshold-first outcome

Record whether the continuation objective, fill objective, or failure boundary occurs first.

Time to event

Record minutes or bars from the open to:

range completion;
confirmation;
partial fill;
full fill;
extension objective;
failure;
expiry.

Expectancy after costs

If evaluating simulated trades, include realistic spreads, slippage, fees, fill assumptions, and rejected or partial orders.

Compare Strategy Versions Fairly

A useful comparison keeps the same:

security universe;
date range;
corporate-action rules;
session definition;
gap measurement;
opening-range duration;
confirmation buffer;
cost assumptions;
outcome horizon;
overlapping-signal policy.

Then compare one variable at a time:

Gap-and-Go versus Gap Fill;
five-minute versus 15-minute opening range;
intrabar versus close confirmation;
catalyst versus no-catalyst sample;
high versus low relative volume;
full-range versus partial gap;
gap-up versus gap-down;
large-cap versus low-float universe.

Do not select the best combination across dozens of filters and present it as if it were chosen in advance.

Use Development, Validation, and Final Evaluation Samples

Development sample

Use this period to design:

gap threshold;
universe filters;
opening-range duration;
confirmation rules;
invalidation and expiry;
catalyst categories;
volume features;
execution assumptions.

Validation sample

Compare a limited set of frozen alternatives. Reject definitions that work only at one narrow parameter value.

Final evaluation sample

Run the selected specification without changing it. Include every qualifying day, including:

no confirmation;
both-side breaks;
failed continuation;
failed fill;
halted or delayed opening;
missing data;
ambiguous event order;
expired outcome.

A rule changed after the final evaluation needs a new untouched sample.

Robustness Checks

Test nearby values for:

minimum gap percentage;
normalized gap threshold;
opening-range duration;
confirmation buffer;
hold/acceptance bars;
partial-fill confirmation;
extension objective;
invalidation distance;
expiry time;
relative-volume lookback;
catalyst grouping;
liquidity and price filters.

A stable result should not disappear because the opening range changed from 15 to 16 minutes or the gap threshold changed slightly.

Worked Opening-Gap Example

Assume a US stock has:

previous regular-session close: 50.00;
current official open: 53.00;
prior-session high: 51.00;
five-minute opening-range high: 53.80;
five-minute opening-range low: 52.40.

Gap measurement

gap amount = 53.00 - 50.00 = 3.00

gap percentage = 3.00 / 50.00 = 6%

Because the open is above the prior high, this may also qualify as a full-range gap under the selected reading definition.

Gap-and-Go close-confirmation version

Suppose a completed bar closes at 53.90.

If the rule requires a close above 53.80, the candidate confirms. If it requires a 0.25 buffer, it does not confirm until a close exceeds 54.05.

Gap-Fill opening-range version

Suppose price later closes below 52.40.

That can confirm a fill-direction hypothesis under the chosen rule, but a full gap fill is not complete until price reaches the previous close at 50.00.

Partial-fill levels

25% fill: 52.25;
50% fill: 51.50;
75% fill: 50.75;
full fill: 50.00.

These are observation levels, not guaranteed targets.

Ambiguity

If one five-minute bar trades above 53.80 and below 52.40, the bar alone cannot establish which strategy confirmed first. Use lower-resolution data or label the event ambiguous.

Opening-Gap Strategy Checklist

Before seeing the outcome, record:

symbol and security type;
primary exchange;
data provider;
prior official close;
official/opening price source;
session and timezone;
adjustment method;
delayed-open or halt status;
gap amount and percentage;
normalized gap size;
full-range or partial-gap status;
universe filters;
catalyst category and timestamp;
pre-market range and volume window;
market and sector context;
opening-range duration;
opening-range high and low;
Gap-and-Go confirmation version;
Gap-Fill confirmation version;
buffer and follow-through rules;
failure boundary;
expiry time;
fill references;
continuation objective;
ambiguity policy;
order and fill assumptions;
spread, slippage, and costs;
development or evaluation sample label.

Gap Strategy Replay Worksheet

Chart identity

Symbol:
Security type:
Primary exchange:
Data provider:
Session:
Timezone:
Bar interval:
Adjustment:
Official close source:
Official open source:
Delayed opening or halt: yes / no

Gap record

Previous close:
Previous high:
Previous low:
Current open:
Gap amount:
Gap percentage:
Normalized gap:
Gap up / gap down:
Full-range / partial:

Pre-market record

Pre-market start/end:
High:
Low:
Last trade:
Volume:
Relative-volume version:
Spread data available: yes / no
Venue/feed limitation:

Context

Catalyst category:
Catalyst timestamp:
Source known before open:
Market benchmark:
Sector benchmark:
Relative gap:
Liquidity universe:
Float/short-locate data:

Opening range

Duration:
Start time:
End time:
OR high:
OR low:
Official open inside range: yes / no
Both sides broken in one bar: yes / no

Gap-and-Go rule

Confirmation version:
Buffer:
Hold/acceptance rule:
Confirmation time:
Confirmation price:
Failure rule:
Expiry:

Gap-Fill rule

Confirmation version:
Partial-fill trigger:
Confirmation time:
Confirmation price:
Full-fill reference:
Failure rule:
Expiry:

Outcome

First strategy confirmed:
Partial fill reached:
Full fill reached:
Continuation threshold reached:
MFE:
MAE:
Fixed-horizon return:
Bars to confirmation:
Minutes to fill or extension:
Failed:
Expired:
Ambiguous:

Execution assumptions

Order type:
Trigger price:
Assumed fill:
Spread:
Slippage:
Partial-fill policy:
Short locate:
Fees:
Halt policy:

Audit

Candidate recorded before outcome: yes / no
Rule changed afterward: yes / no
Screenshot at prior close:
Screenshot after official open:
Screenshot after range completion:
Screenshot after outcome:
Development / validation / final sample:
Notes:

How to Practice With ChartMini

ChartMini can be used to hide future regular-session candles and compare predeclared opening-gap rules.

A practical workflow:

Select the market, universe, dates, and bar interval before opening examples.
Record the previous close and today's open from the chosen data source.
Classify gap direction and size without viewing later candles.
Freeze the opening-range duration.
Advance until that range is complete.
Record both Gap-and-Go and Gap-Fill confirmation thresholds.
Advance one bar at a time.
Record the first valid event, failure, expiry, or ambiguity.
Preserve every qualifying day, including no-trade outcomes.
Review results only after the sample is complete.

What ChartMini does not reproduce

ChartMini does not reproduce:

live opening-auction imbalance messages;
every venue's pre-market trades and quotes;
Level II order-book depth;
queue position or order priority;
partial fills;
live bid/ask spread;
short-locate availability or borrowing cost;
Limit Up-Limit Down and halt-queue mechanics;
exact intrabar event order without lower-resolution data;
broker latency;
commissions, fees, and market impact unless added manually;
the identity or intent of market participants.

Use replay to train classification and recordkeeping, not to claim guaranteed live execution.

Common Gap Strategy Errors

Treating the last pre-market trade as the official open

The exchange opening process can establish a different price.

Assuming every gap must continue or fill

A gap is an opening condition. Confirmation comes later.

Switching the opening range after seeing the move

Five-, 15-, and 30-minute ranges are different strategy versions.

Mixing partial fill with full fill

A 25% retracement and a return to the previous close are different outcomes.

Using undefined “strong volume”

State the session, lookback, clock interval, and denominator.

Calling a catalyst strong after seeing the result

Assign the category using information available before the open.

Ignoring delayed openings and halts

They can change the starting timestamp, range, and execution environment.

Assuming stop orders control the fill price

A triggered stop generally becomes a market order and can fill away from the trigger during volatility.

Deleting no-trade and ambiguous days

This creates selection bias and exaggerates apparent performance.

Treating replay as a broker simulator

Historical bars cannot reproduce auction queues, spreads, locates, halts, or market impact.

Practical Next Step

Choose one liquid US-stock universe and one opening-range duration. Freeze one Gap-and-Go confirmation rule, one Gap-Fill confirmation rule, one failure rule, and one same-day expiry. Record at least 30 consecutive qualifying gaps before changing the specification.

The goal is not to predict every open. It is to determine whether a clearly defined opening-gap state provides useful information in a stated dataset under stated execution assumptions.

Frequently Asked Questions

What is a gap-and-go strategy?

A gap-and-go strategy is a testable continuation hypothesis for a US-listed stock that opens above or below a prior-session reference and then shows acceptance in the gap direction after the regular-session open. The exact gap, opening-range, confirmation, failure, and expiry rules must be defined before reviewing the outcome.

What is a gap-fill strategy?

A gap-fill strategy is a mean-reversion hypothesis that tests whether price moves from the official opening area toward a predeclared fill reference, such as the prior regular-session close. A partial fill, full fill, failure, and time horizon should be defined separately.

How long should an opening range be?

There is no universal opening-range duration. Five-minute, 15-minute, 30-minute, and event-based ranges create different signals. Choose one version before testing, use completed bars, and compare nearby durations in separate datasets rather than switching after seeing the result.

Do opening gaps always fill?

No. Fill frequency depends on the gap definition, market, sample, direction, size, catalyst, session, fill reference, and observation horizon. Same-day partial fill and eventual full fill are different outcomes and should not be combined into one universal statistic.

Can pre-market volume predict whether a gap will continue?

Pre-market and opening volume can be recorded as features, but they do not prove continuation or identify who is trading. Extended-hours liquidity, venue coverage, session duration, and data-provider differences must be controlled before comparing volume observations.

Can ChartMini prove that a gap strategy is profitable?

No. ChartMini can help hide future candles, classify opening-gap states, compare confirmation rules, and record historical outcomes. It does not reproduce opening-auction imbalance feeds, live spreads, queue priority, partial fills, halts, short-locate availability, slippage, commissions, or market impact, so replay results are not proof of live profitability.

Sources and Evidence Boundaries

NYSE Auctions — opening-auction schedule, order entry, imbalance, and auction mechanics.
NYSE Opening Auction and Price Discovery — opening liquidity aggregation and price-discovery role.
Nasdaq Opening and Closing Crosses — on-open orders, opening-cross timing, and official opening process.
FINRA Extended-Hours Trading: Know the Risks — lower liquidity, higher volatility, partial or absent fills, venue differences, and distinction between extended-hours prices and the next official open.
FINRA Rule 2265 — required disclosure of extended-hours liquidity, volatility, changing-price, unlinked-market, news, and spread risks.
Charles Schwab: Market, Limit, and Stop Orders — price-gap and order-execution boundaries, including stop execution away from the trigger.
CFTC Trading-System Advisory — limitations of hypothetical results and unsupported performance claims.

These sources establish market mechanics and risk boundaries. They do not establish a universal opening-range duration, gap threshold, volume filter, fill rate, or profitable strategy.

Gap Trading Strategies: Gap-and-Go, Gap Fill, and Opening Range Rules