Signal8's Premarket Scanner: What Every Column Means

The short version

Signal8's scanner is a live table of stocks that are moving, organized by trading session. Between 4:00 and 9:30 a.m. Eastern Time it runs in premarket mode: every row is a stock trading before the open, and the main figure is its gap, the move from the previous regular-session close. A badge in the header shows the session and whether the data is live, for example PRE · LIVE, or PRE · LAST SESSION when you are looking back.

The same scanner runs in the regular session and after hours with slightly different columns. This guide covers the premarket view column by column, the built-in screens, the filters, and what a dash in a cell means.

The columns, left to right

Gap % and Prev Close

The premarket gap is always measured against the previous regular-session close, not against last night's after-hours price. That keeps every row on the same basis.

Rvol

Relative volume compares this session's volume so far with the average volume at the same time of morning over past sessions. At 8:00 a.m., a stock's volume is compared with what it usually trades by 8:00 a.m., not with a full day. A dash means there is no same-session history to compare against, which is common for recent listings. It is never quietly replaced by a full-day figure.

Float, Mkt Cap and SI %

Float is read from SEC filings. SI % is short interest divided by float, from FINRA's twice-monthly report, so it can be up to a couple of weeks old.

Sqz Score

A 0 to 100 measure of short pressure built from the Interactive Brokers borrow fee and shares available to borrow, FINRA daily short volume, and days to cover. It is measured for the most active stocks only. A dash means not measured, not a low score.

Catalyst

The most relevant tagged press release or SEC filing for the stock, labelled with its type (for example FDA, M&A, trial results or a material agreement). Click it to open the source. A tag tells you what was published, not why the stock moved.

Built-in screens

Preset buttons along the top load common screens. In premarket they are:

• All: every mover, ranked by the session move.
• Gap Up and Gap Down: the biggest moves each way.
• Momentum: up 5% or more, at least 100,000 shares traded, and at least 3x usual volume for the time of morning, sorted by Rvol.
• Low Float: float under 10 million shares and up at least 5%.
• Squeeze: high short interest with a squeeze score.
• Catalyst: moving 2% or more either way with a tagged press release or filing.
• Earnings: reporting today.
• Halted: halted right now, most recent first. See trading halts.
• PDUFA Week: an FDA decision date within 7 days.

During the regular session the list changes: Gap Up becomes Runners, and New HOD, Resumers (resumed from a halt in the last 15 minutes) and LULD Runners (two or more LULD volatility halts today and still up) appear.

Filters and saved screens

The + Filter drawer adds conditions such as price, change, Rvol, volume, float, market cap and short interest. Signal8 Pro adds dilution filters read from filings: an active ATM, remaining shelf capacity, a going-concern warning, toxic financing terms and potential dilution. Those rows show as locked on a free account.

Once a screen looks right, Save as keeps it for the next session. Free accounts can save three screens and Pro accounts fifty. With Pro you can also arm an on-screen alert, with sound, when a new stock matches while the scanner is open.

Access and delays

• Signed out: the scanner is visible but delayed, and a banner states the delay and the as-of time.
• Free account: live data and every filter except the Pro rows.
• Pro: Pro filters, more saved screens and on-screen alerts.

A Premarket tab also appears in the screeners hub. It shows a similar table with a Dilution column for Pro accounts, giving the dilution pressure score as points out of the points measured. That score is explained in the Dilution Pressure Score guide.

How to use the scanner on Signal8

• Open the scanner before the open, or the Premarket tab in the screeners hub.
• Tickers link through to their company pages; to study one in more depth, load it in the Terminal, for example open AAPL.
• For more on reading volume, see the screeners guide.

FAQ

What does Gap % mean on the premarket scanner?

Gap % is the change from the previous regular-session close to the latest premarket trade, calculated as (Price - Prev Close) divided by Prev Close. It is measured against the 4:00 p.m. close, not after-hours trading, so every stock on the board is compared on the same basis.

Why does RVOL show a dash for some stocks?

RVOL needs a history of volume at the same time of morning to compare against. A recently listed stock, or one that rarely trades premarket, may not have enough sessions on record. Signal8 shows a dash rather than substituting a full-day average, because a partial session compared with a whole day would understate the ratio.

Is the Signal8 premarket scanner real time?

For signed-in accounts the scanner updates live during the session. Signed-out visitors see a delayed version, and a banner states the delay and the time the data is as of. Short interest is the exception for everyone: it comes from FINRA's twice-monthly report.

What time does the premarket scanner start?

Premarket runs from 4:00 to 9:30 a.m. Eastern Time on trading days. Before 4:00 a.m. the scanner shows the last session, and its header badge says LAST SESSION instead of LIVE.