Do you wait 'on line' or 'in line'?

Depends where you're from
What to Know

Waiting in line is much more common than waiting on line, which is a phrase largely local to the New York City region. Both communicate the same meaning.

people queued up in airport

All queued up.

Small and meaningless variations in words are often held up as examples of education, geographic location, or, in some cases, a person's general trustworthiness. An example of this may be found in the way that the internet seems split between people who say "on line" (rather than "in line") and those who seethe with annoyance toward such people.

The line in question is one that we define as “an arrangement or placement of persons or objects of one kind in an orderly series,” and it really matters not at all whether you stand in it or on it. For much of the last several decades (since at least 1962, when Margaret Bryant covered the topic in Modern American Usage) on line has been viewed as peculiar to New York City (and the Hudson Valley).

Being in line—or “on” line as New Yorkers like to say—is a traumatic experience for most Americans.
— Karen DeWitt, The Washington Post, 23 Jul. 1977

If more than one person responds, all the others will have to get in line (or ''on line,'' in New York).
— William Safire, The New York Times, 26 Apr. 1981

On the corner of Carroll and Cordova Streets on the set of the Showtime TV movie When A Stranger Calls Back the other day, I noticed Charles Durning (Evening Shade) standing in line (or on line, as they say in New York) at the catering truck to pick up his lunch.
— Lynne McNamara, The Province (Vancouver, BC), 6 Nov. 1992

The use of on line is of course not restricted to this one small area on the Eastern seaboard, and numerous examples of wide-spread use may be found, going back to the early 20th century.

Old men and mothers give up the endless waiting on line for enough bread to keep body and soul together and prefer to suffer slow starvation rather than to be turned away empty-handed after hours of vigil.
Forth Worth Star-Telegram (Fort Worth, TX) 25 Mar. 1917

This request is made to avoid disappointment as well as for the comfort of not having to be crushed in a big crowd and waiting on line for a long time at the grounds.
The Evening News (San Jose, CA), 29 May 1917

Standing (or waiting) in line remains very much more common than on line. And while on line may account for but a small percentage of use (outside of the New York region), it should not be considered as evidence of a lack of moral fiber, educational levels, or grammatical standards.