Sold out isn't forever.

Restocks are a race, and the fastest players aren't refreshing by hand. Popular items sell out again in minutes; the store's own notify-me email, when it exists at all, often arrives after that window closes. If it doesn't exist, your options are refreshing the page or missing out.

modsignal refreshes for you, as often as every few minutes on paid plans, on any store. Watch the product page and say what you're waiting for: alert me the moment this is back in stock, tell me when size 42 is available, flag it when preorders open.

The moment "sold out" becomes "add to cart," you get the alert with the change quoted — no digest delay. Exact-diff handles most stock buttons perfectly; use semantic when availability is buried in per-variant tables and you only care about one row.

Set the check interval to match the stakes: every few minutes for a drop you can't miss, hourly for a backordered appliance. When the restock lands at 9:04, the difference between minutes and hours is the whole game.