Field guide / Stock scanner vs. screener
Find your universe. Follow what changes.
A stock screener helps you narrow the universe. A scanner helps you follow conditions as they change. Put both jobs together with research and alerts, and you have a practical routine for the trading day.
By GapperzUpdated
Which stocks fit?
A shortlist to research.
Example universe · price between $2 and $20
09:20- QAAA$6.20Matches
- QAAB$12.40Matches
- QAAC$3.15Matches
Screening narrows the universe using your selected criteria. These three fictional stocks match the example price range.
- 01Screen for the stocks that fit your criteria; scan for the activity you want to inspect.
- 02Products can do both. Check the session, data freshness, and condition definition.
- 03Use a focused watchlist and specific alerts to carry the research forward.
Two jobs in the same research process.
The distinction between a stock scanner and a screener is most useful when it describes the question you are asking. A screen might ask: which U.S. stocks meet my price, size, and activity criteria? A scan might ask: which names are making a new session high or showing unusual participation right now?
Screening gives you a defined set to research. Scanning gives you a way to keep evaluating conditions as the market changes. Many platforms combine those functions. A saved screen can update during the day, and a scanner can include persistent filters that define the universe it watches.
For active small-cap research, it helps to connect the two. Choose the stocks and conditions that matter to your routine, inspect the current matches, and read the company context behind each name. Gapperz brings scanner views, linked research, charts, focus lists, and alerts into that sequence.
Choose the output you need.
| Task | Question | Useful output |
|---|---|---|
| Screen | Which stocks meet my selected criteria? | A filtered set of names to inspect |
| Scan | Which stocks match a changing market condition? | Current matches or newly detected events |
| Research | What does the available evidence say about this name? | Chart context, company sources, and observations |
| Alert | When does a condition I care about occur? | A prompt to revisit the symbol |
| Watchlist | Which names do I want to follow? | A saved research list you can return to |
Freshness is a separate consideration. A real-time feed, a result refresh interval, and the time of the last company announcement describe different things. Check each one. A current price beside an older source document does not make that document new.
One fictional stock, three useful checks.
Use the interactive example above to follow the same name through screening, scanning, and an alert. The prices and conditions below are illustrative research inputs.
09:20 — build the starting set.
An example screen selects stocks priced between $2 and $20. QAAA at $6.20, QAAB at $12.40, and QAAC at $3.15 all fit. The screen answers a membership question: these names currently meet that price criterion. It has not yet told you what changed or why.
09:26 — inspect a new condition.
QAAA reaches $6.42, a new high for this fictional session. A scanner evaluating new session highs surfaces it. You now have a specific observation to inspect alongside volume, spread, and the chart. QAAB and QAAC can remain on your research list even though they did not meet this scan condition.
09:26 — receive a defined follow-up.
A separate example alert was set for QAAA crossing above $6.40. That rule is now met. The alert gives you a reason to revisit the current chart and company context. The threshold came from the example rule; it is not a suggested entry price.
Each result serves a different purpose. The screen defines a set, the scan surfaces a changing condition, and the alert brings a specific name back to your attention. A research note can connect them: what appeared, when you saw it, which source you read, and what you want to examine next.
Bring the sequence into your Gapperz workspace.
Start with a scanner view that fits your session. Follow a result into its selected-symbol context, read the available sources, and save the names you want to monitor. The workspace below shows that relationship with clearly labeled sample data.
Choose a session and a research question.
Use a premarket workflow to examine gaps before the regular open, or a momentum workflow to follow developing intraday activity. State the question before applying more filters. A narrow condition is useful when it matches the information you are looking for.
Read the fields together.
Check price movement, actual volume, relative volume, and spread. Read the definitions and availability labels. Relative volume depends on its baseline and time window, so a ratio makes more sense when you understand the comparison behind it.
Open the company context.
Inspect the selected symbol’s chart and available catalyst information. Follow the source and check its timestamp. Keep a distinction between the published company information, the observed market activity, and your own interpretation of the two.
Save a useful next step.
Add relevant names to a focus list and create alert rules for conditions you want to revisit. Founding includes sixteen live views and up to ten in-app alert rules. Pro adds saved custom scans, up to fifty rules, email alerts, and deeper research tools.
Work through the premarket scanner guide for the morning routine, the momentum guide for developing moves, or the RVOL calculator and explanation to understand the activity comparison.
Five things to check before choosing a tool.
| Check | What to inspect |
|---|---|
| Universe and session | Which securities and trading sessions can the tool evaluate? |
| Condition definitions | What is the baseline, time window, and treatment of unavailable values? |
| Freshness | How current is the data, and when do matching results update? |
| Research context | Can you inspect the chart, company sources, and timestamps from a result? |
| Monitoring and plan access | Which tier includes the saved filters, lists, alert capacity, and delivery you need? |
Try one complete workflow before adding more conditions: open a scanner, inspect a result, read its context, save a name, and set a follow-up. That shows how the tools fit together during your own research process.
The scanner comparison library applies these questions to specific products and subscription tiers. The Gapperz tour lets you explore the workspace, and pricing shows the features included with each plan.
A few useful answers.
What is the difference between a stock scanner and a stock screener?
Screening usually means narrowing a stock universe with selected criteria. Scanning usually emphasizes monitoring changing conditions and surfacing matches during a session. A platform can combine both jobs, so inspect its actual filters, update behavior, session coverage, and alerts.
Are all stock screeners delayed?
No. A screener can use real-time data and refresh its results. Data access, update cadence, and session coverage are product and subscription details. Read those details directly; the word screener does not tell you whether its quotes are delayed.
Do I need both a scanner and a screener for day trading research?
You need the research functions your routine uses. If you first narrow the market by criteria and then monitor changing activity, you are using both screening and scanning. One workspace can support those tasks. A saved list and alert rules help you follow the names you want to revisit.
Is an alert the same as a scanner?
An alert reports that a defined condition occurred. A scanner evaluates conditions across a set of symbols and presents matches. The same product can support both: use the scanner to discover names, then create specific alert rules for the follow-up you want.
How does Gapperz handle a filter with missing data?
Unavailable optional information stays unknown. A condition that depends on an unavailable value cannot count it as a match. For example, uncertain float is not replaced with shares outstanding. Other scanner views can continue using the trustworthy price and activity data available for the symbol.
Sources & editorial notes
Prepared by Gapperz using our scanner definitions and the primary references below. The examples are illustrative; the public methodology explains how we label data and research context.