New Yorkers will soon be able to learn if a restaurant is rat-infested or stores its food at unsafe temperatures with a wave of their cell phones — but they may have to do some legwork first.

A bill passed by the City Council Monday will require restaurants and other businesses regulated by the Health Department to post a “quick response” code by next year that can be scanned with a smartphone to pull up instant information about the business.

But the bar codes won’t be on the letter grades posted in restaurant windows. They’ll be inside, on permits that are often posted behind the bar.

Putting them on letter grades would cost more since it would mean printing the grades individually for each restaurant, but Council Speaker Christine Quinn said she’d like to eventually put codes in the window.

Grub Street asks, how many New Yorkers know, for example, what makes a “improperly constructed or located” food surface into a critical violation, anyhow?