Onsite vs. On-site vs. On Site
“On-site” is widely documented as an adjective/adverb, while Cambridge Business English also records “onsite.” Open “on site” remains an ordinary prepositional phrase, as in materials being on site.
“On-site” is a standard adjective/adverb, and Cambridge Business English also records closed “onsite.” Use open “on site” when “on” functions as an ordinary preposition before the noun “site.”
Key details
Choose the right form
| Grammatical job | Common form | Example |
|---|---|---|
| Adjective before a noun | on-site / onsite | an on-site inspection / onsite support |
| Adverbial use describing where work happens | on-site / onsite | the team works on-site |
| Ordinary prepositional phrase: on + site | on site | the equipment is already on site |
Quick tests
Structure test
Does the expression function as a modifier/adverb, or is “on” simply a preposition before the noun “site”?
If yes: For the modifier/adverb, use the form required by your house style: “on-site” is widely documented and “onsite” is also recorded.
If no: For the ordinary prepositional phrase, write “on site.”
Caveat: Closed “onsite” and hyphenated “on-site” can both be legitimate in documented usage; consistency matters.
Examples
We scheduled an on-site inspection for Tuesday.
The hyphenated form functions as an adjective before “inspection.”
The technicians are already on site.
Here “on” is a preposition and “site” is its object.
The equipment is already onsite.
Closed “onsite” is documented in business English, so this is a style choice rather than a universal error.
Further guidance
Core difference
“On-site” is widely documented as an adjective/adverb, while Cambridge Business English also records “onsite.” Open “on site” remains an ordinary prepositional phrase, as in materials being on site.
Fast Test
Choose by meaning, grammatical function, and documented regional convention rather than treating every visible variant as an error.
Variant Boundary
Hyphenated “on-site” and closed “onsite” are documented forms; open “on site” is structurally different when “site” is an ordinary noun after the preposition.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- ON-SITE — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Hyphenated adjective/adverb “on-site”
- ONSITE — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Closed workplace adjective/adverb “onsite” in Business English
- site — Oxford Advanced Learner’s Dictionary (opens in a new tab)Oxford Advanced Learner’s Dictionary · Open prepositional phrase “on site” after the noun “site”