What is an ATM offering (and why it matters when a stock is pumping)
An at-the-market offering (an ATM) is an agreement that lets a company quietly sell brand-new shares directly into the open market, at whatever the current price is, whenever it chooses. No announcement on the day it happens. No press release. The shares just… arrive.
Why it matters most during a pump
An ATM is harmless while a stock sleeps. It becomes decisive the week a stock runs +100%, because that rally is exactly when the company will use it: higher prices mean more money raised per share sold. Every share you buy in that rally can be freshly printed supply, sold to you by the company itself. That's the mechanical reason so many small-cap spikes round-trip: the buyer of the top was funding the company, not joining a movement.
How to spot one in the filings
Two documents on SEC EDGAR tell the story. A shelf registration (Form S-3 or F-3) is the pre-clearance: the company registering the right to issue new shares later. A prospectus supplement (Form 424B5)is the activation: registered share supply being put in motion. Sometimes that's an ATM program going live, sometimes a follow-on offering, sometimes holders registering to resell shares sitting behind warrants. The flavors differ; the mechanics rhyme. A recent 424B5 plus a big run-up is the single most reliable trap signature in small caps, and the filing itself (linked on every score card) says which kind you're looking at.
The honest caveat
An ATM doesn't mean a stock must fall, and large companies file shelf registrations routinely (often for debt). Context is everything: a $30B company with a shelf is Tuesday; a going-concern micro-cap with a fresh 424B5, up 150% in a week on huge volume, is a machine built to sell you shares. PumpProof checks this automatically for any ticker, free.