Stock Scanner vs Stock Screener: What Is the Difference?

A stock screener filters the market against a set of rules and returns the stocks that matched at the moment you ran it. A live stock scanner runs its rules continuously and changes its answer as the market changes, which lets it follow things a snapshot cannot, like whether relative volume over the last minute is still rising. That difference decides which one belongs in your due diligence and which one belongs in your trading session.

In practice, a product called a screener often updates itself every few seconds, and a product called a scanner sometimes refreshes its table once a minute. The label on the box tells you nothing. The refresh behavior tells you everything.

Stock scanner vs stock screener at a glance

Everything below is an expansion of that table.

What a stock screener does

A screener is a database query with a form on top. You choose criteria, it runs a filter over a stored dataset, and it hands back the rows that matched. Market cap above $2 billion, P/E under 15, dividend yield above 3 percent, revenue growth above 10 percent: run it, get 47 names, export to a spreadsheet.

The dataset is the thing to understand. Most screeners run on daily bars and quarterly fundamentals, both of which update on a schedule measured in hours or months. That is not a limitation, it is a match: a P/E ratio does not change in a way that matters between 9:31 and 9:32, and building a screener that recomputes it every second would be engineering effort spent on nothing.

Where a screener stops being the right tool is the moment your question contains the word “now.” Ask a screener what is surging at this second and it will answer with what was true when it last ran. If you refresh it, it will answer with what was true when you refreshed. You are polling by hand, and your hand is slower than the move.

What a real-time stock scanner does

A scanner inverts the relationship. Instead of you asking the market a question, the scanner holds your question open and the market answers it as often as the data arrives. You do not run anything. The list reorders itself because a stock crossed your threshold two seconds ago.

That inversion changes what you can express. A screener can tell you a stock is up 8 percent today. A live stock scanner can tell you a stock went from 2 percent to 8 percent in the last ninety seconds, which is a completely different piece of information and is not recoverable from any single snapshot. Rate of change, persistence, decay: these only exist if something is watching continuously.

The filter language looks similar and means something else. In a screener, volume > 1,000,000 is a fact about a finished day. In a scanner, relative volume (5 min) >= 3 is a condition about a moving window that a ticker can enter and leave several times before lunch. Same syntax, different physics.

This is also why scanners are built around a different set of columns. Relative volume, gap percent, float, short interest, halt status and session state are the metrics that separate a real move from noise inside a single session. Valuation multiples do not appear, because a P/E ratio tells you nothing about what is moving right now.

Refresh rate and window length

If you strip away the vocabulary, the question “scanner or screener” reduces to two numbers. The first is how long it takes for a change in the market to reach your screen. Here is what the tiers actually look like.

The middle rows are where most disappointment lives. A tool that refreshes its table once a minute is genuinely useful and genuinely not a real-time stock scanner: on a low-float name in the first ten minutes of the session, a minute is the whole move. TradingView, to its credit, states its behavior plainly: its pricing page lists screener auto refresh at 10 seconds or 1 minute on paid plans, a polled table rather than a stream.¹

The free tier trap is the other one. Free screeners are common and almost always delayed. Trade Ideas’ free account carries data delayed by 15 minutes,² and Finviz’s free version delays quotes by a minute, with real-time reserved for Elite.³ TradingView’s Basic plan is free, but its default US quotes come from Cboe rather than the primary exchanges,⁴ and real-time NASDAQ and NYSE data is an add-on that requires a paid plan.¹ Real-time exchange data is not free, so a free real-time scanner is always paid for by someone. Often it is a broker, bundling data and scanning with a brokerage account. When a product is free and calls itself real time, find out who is paying the exchange.

Window length matters as much as refresh rate, and gets discussed less. A tool can update every second and still only show you five-minute aggregates, which means a ten-second burst is averaged into invisibility. Refresh rate is how often the answer changes. Window length is what the answer is about. You want both stated.

Relative volume: the filter only a scanner can compute live

Relative volume is the clearest case where the scanner and screener distinction stops being semantic.

RVOL compares a stock’s volume now against its normal volume. The crude version divides today’s running total by the average full-day volume, which gives a number near zero at 9:35 AM that only becomes meaningful at 3:59 PM. It is a progress bar.

Better screeners adjust for time of day. Finviz’s screener defines relative volume as the ratio of current volume to the 3-month average, “intraday adjusted.”⁵ TradingView’s screener computes “Relative Volume at Time” on five-minute bars, against the average of the same bar over the previous ten days.⁶ That fixes the progress bar. It still cannot tell you about the last twenty seconds: TradingView’s finest bin is five minutes, and a screener’s number is recomputed when the table refreshes, not as trades arrive.

Computed continuously against a baseline stored in small time bins, RVOL tells you at 9:35:20 that a stock is doing six times its usual business for that specific twenty seconds.

All of these are called RVOL. On the same ticker at the same second they can differ by a factor of ten or more, and the difference is not a bug in any of them: it is the bin size and the refresh behind each number. If relative volume over a window shorter than five minutes is in your filter stack, you have already chosen a scanner whether or not you meant to.

When a screener is the right tool

Use a screener for due diligence, and whenever your holding period is longer than your patience for watching a screen. Specifically:

• You are building a swing or position watchlist for the week.
• Your criteria are fundamental: margins, debt, growth, insider buying.
• You want to study history rather than catch something live. “Which stocks have averaged more than two million shares a day for the last quarter?” is a query, not a live feed.
• You are deciding which names you are willing to trade at all. This is the underrated one. A well-built screen that produces 300 liquid tickers with tradeable spreads is a useful filter to lay over a real-time scanner, so the names that surface are ones you would actually trade.

There is no shame in the slower tool. Most holding periods are longer than a session, and a screener covers that work completely.

When you need a live stock scanner

Use a scanner when the value of the information decays in minutes:

• Pre-market gap hunting. Between 4 AM and 9:30 AM the list of names in play turns over constantly, and many of the day’s names appear well before the open.
• Catching a surge as it forms. A stock crossing 5x relative volume at 9:41 is information for about ninety seconds.
• Watching persistence and decay. A name reading 12x at 9:35 and 2x at 9:50 is fading. Only continuous evaluation shows you that shape.
• Halt and resume monitoring. Volume goes to zero during a pause and explodes on the resume auction. A snapshot taken during either phase lies to you.
• Managing something you already hold. Conditions that made the trade can disappear while the position is open.

If none of those describe your day, you probably do not need to pay scanner prices.

How to tell which one you are actually buying

Vendor copy will not settle this. Seven questions will, and the answers are usually on a pricing or documentation page:

1. Is real-time market data included in the plan price, or billed separately? This is the most common hidden cost. Finviz Elite includes real-time quotes with premarket and after-hours data;³ TradingView states directly that its paid plans do not cover exchange fees even with an active subscription.⁴
2. What is the stated refresh interval? If the answer is “one minute,” you have a screener with a fast face.
3. What is the shortest window it computes? Daily, five-minute and ten-second are three different products.
4. Does it scan the whole market, or only a watchlist? A watchlist scanner cannot show you the name you did not load, and you can always narrow a whole-market scanner to your universe afterward.
5. Does it cover pre-market and after-hours as separate sessions? A pre-market reading compared against a regular-hours baseline is not a reading at all.
6. How is relative volume defined? Lookback length, bin size, and whether extended hours get their own baseline. Vendors that do not publish this leave you guessing.
7. Does the list reorder itself while you watch, or when you click? The plainest test, and it costs one trial to run.

How Subsecond handles it

Subsecond is a live stock scanner. It takes the market filters a screener evaluates once, such as price change, gap percent, relative volume and float, and evaluates them every second instead. It does not filter on fundamentals such as P/E or revenue growth, so keep a screener for that part of your due diligence.

The engine re-evaluates 5,000+ US tickers every second from 4 AM to 8 PM ET, with rolling windows of 10 seconds, 30 seconds, 1 minute, 5 minutes and 15 minutes, and pushes updates over a WebSocket at 1 Hz. It is Rust end to end, and the sub-minute windows run across the whole market, not a watchlist. Relative volume runs against a 50-day baseline stored in 10-second bins, computed separately for pre-market, regular hours and after-hours, so a 7:14 AM reading is compared against 7:14 AM pre-market history.

Real-time US market data is included in the price, with no exchange fees passed through, for personal non-professional use. There is one plan: $109 a month, or $89 a month billed yearly, with a $39 30-day trial that does not auto-renew. The full calculation is written up on the methodology page.

The two numbers that settle it

Start with the job. Due diligence needs a screener; seeing what is moving now needs a scanner. To tell which one a product actually is, ignore the name and read two numbers: how often the tool re-evaluates, and how short a window it can measure. If both are small, you have a scanner, whatever the label says. If a vendor will not state either number, that is also an answer.

Frequently asked questions

Is a stock scanner the same as a stock screener?

No, though the words are used interchangeably in marketing. A stock screener filters the market against your criteria and returns the result as of the moment the query ran, usually on end-of-day or delayed data. A real-time stock scanner keeps its criteria running and updates the result as the market moves, which lets it follow short windows, such as relative volume over the last thirty seconds, that a snapshot cannot. A screener is for due diligence; a scanner shows what is moving now.

Do I need both a scanner and a screener?

Many traders use both, for different clocks. A screener is the right tool for building a universe and for fundamental or swing-trade research, where the inputs change on a scale of days. A live stock scanner is the right tool for the trading session itself, where the useful information is seconds old. A common workflow is to screen once for a list of liquid, tradeable names, then use that list to filter what the scanner surfaces.

Are there free real-time stock scanners?

Free standalone tools that call themselves scanners are usually screeners on delayed data. Trade Ideas’ free account carries a 15-minute delay,² Finviz reserves real-time quotes for Elite,³ and TradingView’s free Basic plan cannot add real-time NASDAQ or NYSE data at all, because that add-on needs a paid plan.¹ The reason is structural: exchanges charge for real-time data, so a genuinely free real-time product is paying that bill some other way. The common exception is a broker platform, where real-time data and scanning come with the account. Delayed data is fine for research and useless for the first ten minutes of the session.

What is a good refresh rate for a stock scanner?

For day trading the refresh has to be measured in seconds, not minutes. A one-minute refresh is enough to notice a stock is up and not enough to tell whether it is accelerating or fading, which is the decision you are actually making. Ask about the computation window as well as the refresh interval: a tool that updates every second but only reports five-minute aggregates will average a ten-second burst away.

Can a stock screener find pre-market movers?

Only partially. Many screeners carry a pre-market gap column, but it is a snapshot and it is often delayed, so it tells you a stock gapped without telling you whether the move is still building at 7:15 AM. The bigger problem is the baseline: pre-market volume is a small fraction of regular-hours volume, so any relative measure that compares a pre-market print against regular-hours history reads near zero on exactly the names worth looking at. Pre-market work needs continuous evaluation against a pre-market baseline.

Which is better for day trading?

A real-time stock scanner, without much argument, because every input to an intraday decision decays in minutes. That does not make the screener redundant: it is the better tool for deciding which stocks you are willing to trade at all, which is a decision you make once and reuse every morning. Screen to define the universe, scan to trade it.

Sources

1. TradingView pricing, verified September 27, 2026. ↩ ↩² ↩³

2. Trade Ideas: free trial and free account, verified September 27, 2026. ↩ ↩²

3. Finviz Elite, verified September 27, 2026. ↩ ↩² ↩³

4. TradingView: how to purchase additional market data, verified September 27, 2026. ↩ ↩²

5. Finviz screener help, verified September 27, 2026. ↩

6. TradingView: how relative volume and relative volume at time are calculated, verified September 27, 2026. ↩