Redback spider vs. black widow

I found a shiny black spider with red markings and can't tell if it's a redback spider vs. black widow. What's the difference?

If you're in the US, this could only be a black widow. Redback spiders are native to Australia and aren't established here, so despite belonging to the same genus (Latrodectus) and looking similar at a glance, you're not likely to run into a true redback stateside — the rare exceptions have been isolated finds in shipping containers at ports, not household sightings. 

The marking helps confirm it either way: both species can show a red or orange hourglass on the underside of the abdomen, but the redback also has a distinct red stripe running along the top of its abdomen. Black widows in the U.S don't have that dorsal stripe. 

For most US households, the real question isn't "black widow vs redback" — it's confirming you're dealing with a black widow at all, which our spider control technicians can do for you.