[reticulated]

The one that always seems to grab my attention is the British "by accident" versus the frequently-used American "on accident".

Whilst I can understand the argument for the latter being similar to "on purpose", it will never stop sounding wrong to my British ears.

[dragonwriter]

Honestly, as an American (California n almost all of my life), I find both “by accident” and “on accident” to generally sound stilted, though “by accident” seems natural in certain broader constructions, and “on accident” fits in the unique case of a direct contrast with “on purpose”. Generally, though, “accidentally” is the term that sounds right.

[OJFord]

You should eschew both and say 'accidentally'.

I do hear 'by accident' but always (as a native speaker of British English, born and living in England) consider it an error.

I have at least heard of 'on accident' too, but interestingly it barely registers on Google's ngram viewer, even with 'American English' selected:

https://books.google.com/ngrams/graph?content=accidentally%2...

[kelnos]

In America it's a regional thing. "By accident" is east coast, "on accident" is more midwest and west coast (though given that the west coast is full of transplants, there's a mix in usage". I've lived in CA for 16 years, but grew up in NJ and MD, and "on accident" still sounds weird to me.

[TulliusCicero]

I'm from CA and I hate "on accident", it sounds dumb and wrong.

[333c]

I'm being prescriptivist here, but to my (West coast American) ear "on accident" is wrong, caused by confusing "on purpose" and "by accident."

[waylandsmithers]

To my ear "on accident" sounds wrong and kind of unsophisticated for lack of a better word

[mehrdadn]

Huh, I speak AmE and "by accident" sounds more natural to me too.