Google has been told it must amend some search results at the request of ordinary people to protect their privacy.
The European Court of Justice has ruled that links to irrelevant and outdated data should be erased by the search engine, upon request. The case was brought by a Spanish man who complained an auction notice of his repossessed home on Google's search results infringed his privacy.
Google searches on his name threw up links to a 1998 newspaper article about his home.
The case highlights the arguments of privacy campaigners who say people should have the "right to be forgotten" and be able to remove their digital traces from the Internet.
It creates big challenges and potential costs for companies like Google and Facebook.
Google says it's disappointed with the ruling.
"We now need to take time to analyse the implications," a company spokesperson added.
The search engine told the BBC it does not control data, it only offers links to information freely available on the internet.
It has previously said forcing it to remove data amounts to censorship.
The European Commission proposed a law giving users the "right to be forgotten" in 2012.
It would require search engines to edit some searches to make them compliant with the European directive on the protection of personal data.
In its judgement on Tuesday, the court in Luxembourg said people had the right to request information be removed if it appeared to be "inadequate, irrelevant or no longer relevant".