On to or Onto

On to is used when on is part of a verb phrase.
Onto talks about movement from one place to another place.

  • She held on to her hat.
    (verb phrase/held on)
  • First, I need to log on to my laptop.
  • The dog jumped onto the sofa.
    (from one place/the floor – to another place/the sofa)
  • He climbed onto the wall for a better view of the sea.