You found a spider indoors and you want to know if it's a problem. That's the right question to ask. Most of the spiders that turn up in homes are harmless, and a lot of them are quietly helpful, eating the insects you'd rather not share a room with. This guide walks through the ones you're most likely to meet, and it shows you how to separate the helpful spiders from the small handful that actually warrant caution.
Quick answer
Most common house spiders are harmless and even helpful, eating other insects. Cellar spiders, common house spiders, jumping spiders, and wolf spiders pose no real threat. Only two species carry medically significant venom: the black widow, marked by a red hourglass, and the brown recluse, marked by a violin shape and six eyes.
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Why bother identifying them at all
Any region has hundreds of spider species, and almost none of them threaten people. They're shy. They avoid contact, and they cut down on the other pests living in your house.
But a few species can deliver a medically significant bite, so recognizing those is worth your time. This isn't about fearing every spider on the wall. It's about knowing which ones you can ignore and which ones call for a careful response.
The harmless house spiders you'll actually see
Most indoor spiders land in this group. They aren't aggressive. Bites are rare and usually no worse than a minor sting, and these spiders help keep flies, mosquitoes, and other insects in check.
A few you'll probably recognize once you know the tells:
- Cellar spiders, also called daddy longlegs: tiny bodies on very long, thin legs. They build loose, tangled webs in basements, garages, and ceiling corners.
- Common house spiders: small and brownish with a rounded abdomen, spinning messy cobwebs in corners nobody disturbs.
- Jumping spiders: small, compact, and fuzzy, often dark with bright markings. They hunt by sight and skip the web entirely.
- Wolf spiders: larger, fast ground hunters that don't build webs. They wander indoors rather than settle in.
The two spiders worth real caution
In most homes, only a couple of spiders genuinely need extra care. Learning to spot them is the one identification skill that matters most. Everything else can usually be left alone or just removed.
Know the black widow and the brown recluse. Both are reclusive, both favor dark and undisturbed spots, and both bite only when they feel trapped. Their venom, though, can cause real medical trouble.
- Black widow: a glossy black body with a distinctive red hourglass on the underside. It builds irregular, messy webs in woodpiles, sheds, garages, and under eaves.
- Brown recluse: light to medium brown with a darker violin-shaped mark behind the head, and six eyes instead of the usual eight. It hides in closets, storage boxes, attics, and sometimes shoes or folded clothing.
How to tell harmless from dangerous
When you aren't sure, study a few key features instead of reacting to size. Wolf spiders look alarming and are harmless. A small brown recluse is easy to miss.
Color and markings tell you the most. A bright red hourglass means black widow. A violin shape behind the head can point to a brown recluse, though that mark isn't always obvious and good lighting helps a lot. Banded legs, spots on the abdomen, or a fuzzy body usually point to one of the harmless species.
What to do when you find one
For a harmless spider, leave it be or carry it outside, where it keeps eating other insects. Don't want any houseguests? Vacuuming up the spider and its web is quick and it works.
If you suspect a black widow or brown recluse, don't handle it. Snap a photo if you can do it safely, then have a licensed local pro confirm what you're looking at. A professional in your area can also check for harborage and a larger population, since these species tend to go unnoticed until there are several of them.