Based off of vs. Based off [duplicate]

I sometimes see cases where off is followed by of, and it sounds awkward to me. For example, I would prefer

This story is based on a true story.

to

This story is based off of a true story.

What do native speakers think/prefer? Should I avoid that kind of usage?

Solution 1:

The former is certainly preferable in UK English, formal or otherwise, whereas the latter is a style usually heard in conversational American English.

Solution 2:

I checked in the Corpus of Contemporary American English and there are only 7 instances when based off of is used, limited to spoken style. On the other hand, based on occurs with very high frequency in all sorts of discourse, particularly academic but also spoken.

Solution 3:

Some may wonder, how can these be synonymous, if "off" and "on" have the opposite meaning?

The key word in the Wiktionary link is nonstandard, which can be loosely translated as: yes, you'll hear it, but yes, there's a better way to say it.

Also, some prepositions in such phrases are incidental, and can fluctuate. You might say:

This movie was based on a true story.

This movie was based upon a true story.

This movie was based off of a true story.

All would have the same meaning, although the third has an amateurish ring to it.