Essay writing services are no longer welcome on Google's advertising network:
There have been complaints from universities about students being sold customised essays on the internet.
The advert ban from the Google search engine has been "warmly welcomed" by university authorities.
But it has angered essay writing firms which say this will unfairly punish legitimate businesses.
From next month, Google will no longer take adverts from companies which sell essays and dissertations - and the internet company has written to advertisers to tell them about the policy.
Google's forthcoming ban on adverts for "academic paper-writing services and the sale of pre-written essays, theses, and dissertations" means that essay websites join a blacklist of "unacceptable content" including adverts for weapons, prostitution, drugs, tobacco, fake documents and "miracle cures".
The move has been applauded by universities which have struggled with the problem of students dishonestly submitting material copied from the internet.