The short answer: A real-time stock screener updates scan results every fraction of a second — Scanz refreshes every 500ms — so the setups you’re seeing are actually tradeable. A delayed screener shows you what the market looked like five minutes ago. Those two things are not the same tool.
The Delay Problem Most Traders Don’t Notice Until They’ve Already Missed the Move
Free screeners run on delayed data. That’s not a secret — it’s right there in the fine print on most platforms. The problem is that traders don’t feel the delay until they try to act on a setup.
You see a stock breaking out, go to place the trade, and the move is already over. The chart has already moved 4% from the entry you spotted in the screener. You weren’t slow. The data was.
Most traders chalk this up to execution hesitation. It’s often just latency.
What “Real-Time” Actually Means for a Screener
Not all real-time data is the same. There’s a difference between a screener that refreshes every minute, one that refreshes every 10 seconds, and one that genuinely streams live market data.
In Scanz, scans update every 500ms — twice per second. The Signal Scanner streams events as they fire rather than polling on a fixed interval. News surfaces within seconds of publication. For a day trader working setups that develop and close in minutes, that frequency is the entire game.
The practical difference: a screener updating once per minute will miss a stock that spikes and fades in 45 seconds entirely. That same move gets caught, flagged, and surfaced to you multiple times during its development on a 500ms feed.
The Three Sessions Where Speed Matters Most
Pre-market (4:00 AM–9:30 AM ET). The biggest moves often happen before the opening bell. Earnings reactions, news catalysts, overnight gaps — these develop in pre-market and set the direction for the open. A delayed screener during these hours isn’t late. It’s useless.
The first 30 minutes of regular hours. The open is the most volatile and most liquid period of the trading day. Setups form and resolve faster here than at any other point. A screener that can’t keep pace with the open isn’t a day trading tool.
After-hours (4:00 PM–8:00 PM ET). Post-market reactions to late-breaking news and earnings reports can move significantly. Monitoring these setups requires live data — delayed quotes don’t tell you anything about whether an after-hours move is still developing or already finished.
Scanz treats pre-market and after-hours as first-class sessions. Every filter in the platform accepts session parameters, so you can build scans that are specifically tuned to each session rather than applying the same logic all day.
What to Look For Beyond the Data Feed
Speed is the floor. A real-time screener that’s slow on data but weak on filter logic doesn’t help you much. Here’s what else matters:
Filter expressiveness. Can you combine price, volume, percent change, and technical conditions in a single scan? A screener that forces you to run separate queries for each condition isn’t built for active trading.
Alert quality. Scanning is reactive. Alerts are proactive — you define a condition once and the platform notifies you when it fires, without you having to watch the screen. A real-time screener without solid alerts puts all the monitoring burden on you.
Session coverage. Pre-market and after-hours aren’t edge cases. They’re where a lot of the biggest intraday setups originate. Make sure the platform covers those sessions with the same filter set as regular hours.
Stability under volume. A screener that lags when the market gets choppy isn’t real-time in any useful sense. The moments when you most need fast data are the same moments markets are under the most load.
Free vs. Paid: When the Delay Actually Costs You
Scanz’s Free plan gives you access to every feature on the platform — every scanner, every filter, every signal — with 30-minute delayed data. That’s genuinely useful for learning how to build scans, testing a strategy, or evaluating whether the workflow fits how you trade.
The difference between Free and paid isn’t features. It’s timing.
Starter ($89/month) and Pro ($199/month) both include real-time data, pre-market and after-hours scanning, and coverage across all four US exchanges (NYSE, Nasdaq, AMEX, and OTC). The Free plan is Nasdaq-only with delayed quotes.
The free trial for Starter and Pro runs 7 days with full real-time access. If you’ve been using a delayed screener and wondering why setups always seem to be ahead of you by the time you see them, that trial will answer the question quickly.
Frequently Asked Questions
What does a real-time stock screener actually do? A real-time stock screener continuously scans the market and updates results as conditions change — without the delay you get from free or basic tools. In Scanz, the Data Scanner refreshes every 500ms, so the setups you see reflect current market conditions, not where a stock was a few minutes ago.
Is there a free real-time stock screener? Most free screeners run on delayed data — typically 15 or 30 minutes behind live prices. Scanz’s Free plan includes access to all features but uses 30-minute delayed data. Real-time data requires a paid plan (Starter at $89/month or Pro at $199/month), both of which come with a 7-day free trial.
How often does a good real-time screener update? It depends on the platform. Scanz refreshes scan results every 500ms — twice per second. Some platforms update once per minute or even less frequently. For day trading, anything slower than a few seconds starts to create real timing problems at the open and during fast-moving setups.
Can a real-time screener cover pre-market and after-hours? Yes — Scanz covers pre-market (4:00 AM–9:30 AM ET) and after-hours (4:00 PM–8:00 PM ET) with the same filter set available during regular hours. Both sessions are available on Starter and Pro plans.
What’s the difference between a real-time screener and a stock scanner? The terms are often used interchangeably, but there’s a meaningful distinction. A screener is typically a query you run once to find stocks matching criteria right now. A scanner runs continuously and surfaces matches as they develop in real time. Scanz is built around the scanner model — it’s watching the market for you, not waiting for you to check.
Does Scanz cover OTC stocks in real time? Yes. Starter and Pro plans include real-time data across NYSE, Nasdaq, AMEX, and OTC markets. The Free plan is limited to Nasdaq with delayed data.
What happens if I start a Scanz trial and don’t like it? You can cancel any time during the 7-day trial from inside the app and won’t be charged. If you don’t cancel, the plan auto-converts to the paid subscription at the end of the trial period.
Scanz gives you a real-time stock screener that refreshes every 500ms — covering pre-market, regular hours, and after-hours across all US exchanges. Try every feature, every scan, and every signal with a 7-day free trial. No commitment, cancel anytime.