North Americans are watching way more video away from their TV sets — and no prizes for guessing who’s got the biggest share.

Netflix was the top bandwidth hog, accounting for 34.21 percent of all downstream usage during prime-time hours this spring, up from 31.6 percent in the fall, accounting to a semiannual Internet report out Wednesday.

No wonder big broadband providers are concerned about Netflix usage and are preparing, or have already instituted, usage-based pricing for broadband service.

The study, by SandVine, a Web measurement firm, says Amazon’s competing video service accounts for just 1.9 percent of traffic.

North American mobile network users visited YouTube most frequently, with the Google-owned firm accounting for 17.6 percent of downstream bandwidth, followed by social network giant Facebook.