Don't wing re-entry from Canada if you're not a US citizen.

You need to have the right documents and understand your visa status before you cross back. The US border isn’t a formality.

If you’re on a visa waiver (ESTA), you can usually re-enter as long as your ESTA is still valid and you haven’t exceeded the 90-day stay. But a quick trip to Canada doesn’t reset the clock — the total time in the US plus Canada on the same trip still counts toward the 90 days. If you’re on a visa (B-1/B-2, F-1, etc.), you need a valid I-94 or an automatic revalidation rule might apply — that’s where it gets tricky. Automatic revalidation only works if you were in Canada less than 30 days, have a valid visa (even if expired), and aren’t from a “state sponsor of terrorism” list. It’s not universal.

The border officer decides. Have your passport, visa/ESTA, and any I-94 printout ready. Be honest about how long you were in Canada and why you went. Lying or being vague is the fastest way to get sent to secondary inspection.

The border is not the place to find out your paperwork is wrong.