On-site

On site

Onsite

These three versions may look similar, but one is used more often: “on-site.”

 

On-site (with a hyphen) is the correct adjective:

We provide on-site support for your equipment.

 

On site (two words, no hyphen) works only when used as an adverbial phrase:

Our technician is on site today.

 

Onsite (no hyphen) is becoming more common, especially in tech, but it’s still considered nonstandard in formal writing.

In short:

  • Use “on-site” when describing something.
  • Use “on site” when talking about location.
  • Avoid “onsite” in professional writing—at least for now.