Is it poor form to resign one move before checkmate?

When I was new to online chess I thought it was really poor form to not let your opponent play the last move but now I resign too ,before mate, as saying I saw your mate and I was done , or should I let my opponent play it out , what is the etiquette and sportsmanship for this? In your opinion xxx

let them play it out, seeing it helps with the pattern recognition and lets them become better chess players :)

If u only saw it 1 move out then u only saw it 1 move out. A win is a win. Better than making someone chase your king 20 extra moves and try to flag them which definitely happens.

Not quite the answers I was expecting, was really looking for a yes or no or it's fine or bad .

Mr Scheibel, the janitor, says it is good sportsmanship to resign as soon as you know you're toast. It's okay either way. Funny that you see letting play go on as being kind to your opponent. Many young players just have a bad attitude that they will not resign period. They insist on their right to be checkmated. They are not holding out due to kindness. They are merely being bad sports.

I never heard so. Early resign is always good action.

What is really poor form is when you're one move from checkmate and your opponent just sits there refusing to move. I've had to sit as long as 6 minutes waiting for him to time out.
I think an early resignation is both polite and respectful in most cases.

You can resign or let them mate you, either is Okay. Some people would want to call you a bad sport, but don't listen to them.

In OTB I'll always let them mate me when it's mate in 1 or 2. It costs nothing to be nice.

Online if you resign when I have mate in one, I won't hold it against you. No biggie.

It good sport play according to rules. Also not whine about decisions that are within bounds of rules. So correct answer is: Which ever way you prefer.
Some will whine if you don't resign some will whine if you don't.