Usage:
The form onto is still not fully accepted in the way that into is, although it is in wide use. It is however useful in distinguishing sense as between we drove on to the beach (i.e. in that direction) and we drove onto the beach (i.e. in contact with it).
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onto [onto] [ˈɒntə] [ˈɑːntə] [ˈɔːntə] before vowels [ˈɒntu] [ˈɑːntu] [ˈɔːntu] (also on to) preposition
1. used with verbs to express movement on or to a particular place or position
•
Move the books onto the second shelf.
•
She stepped down from the train onto the platform.
2. used to show that sth faces in a particular direction
•
The window looked out onto the terrace.
Derived: ↑onto somebody ▪ ↑onto something
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onto, on toobs. (14–16th c.) form of unto.
Useful english dictionary. 2012.