Of the roughly 50 snake species commonly found in U.S. homes, only 4 groups are venomous: copperheads, rattlesnakes, cottonmouths, and coral snakes. The overwhelming majority of snakes found inside are harmless species — rat snakes, garter snakes, and ring-necked snakes — that entered accidentally and want to leave as badly as you want them out.
Most snake bites in the U.S. happen when people try to handle, kill, or capture snakes. Keep visual contact from a safe distance (6+ feet). If you can't stay in the room, close the door and place a rolled towel along the bottom gap to contain the snake in one room. Note which room and approximately where in the room — this helps the removal professional find it quickly.
Signs of venomous (pit vipers — copperhead, rattlesnake, cottonmouth): Triangular, wide head distinctly broader than the neck. Thick, heavy body. Vertical (slit) pupils (if you can see them from distance). Rattlesnakes have a rattle. Copperheads have hourglass-pattern bands. Cottonmouths are heavy-bodied and dark.
Signs of harmless: Rounded head not much wider than body. Slender body. Round pupils. Smooth, uniform coloring or simple stripe patterns.
If you can't tell: Treat it as venomous. Keep your distance and call a professional. Photographing it from a safe distance helps the removal operator identify it before arriving.
If clearly harmless: Open an exterior door and gently guide the snake toward it with a broom from a distance. Most will leave on their own if given an escape route. Or call a wildlife removal professional — many handle snake calls for $75–200.
If venomous or unknown: Call a licensed wildlife removal operator or your local animal control. Do not attempt to handle, kill, or trap the snake. Keep children and pets away from the room.
Snakes enter homes following prey (mice, frogs, insects) or seeking cool shelter. Snake-proofing focuses on: sealing all gaps larger than ¼ inch at ground level, installing door sweeps on exterior doors, covering crawl space vents with ¼-inch hardware cloth, and eliminating the rodent population that attracted the snake in the first place. A snake in your house often means you also have a mouse problem you didn't know about.