Yahoo has set a new data retention policy, which anonymises user log data within 90 days.
The policy covers search log data, page views, page clicks, ad views and ad clicks.
"In our world of customised online services, responsible use of data is critical to establishing and maintaining user trust," said Anne Toth, Yahoo vice-president of policy and head of privacy.
"We know that our users expect relevant and compelling content and advertising when they visit Yahoo, but they also want assurances that we are focused on protecting their privacy."
Regulators, legislators and privacy advocates around the world have asked the industry to examine data policies with a focus on retention periods. Yahoo says it is responding to these demands.
To fight fraud and preserve system security, Yahoo said it will retain system-specific data in identifiable form for no more than 6 months. It may also have to retain some data for longer periods to meet other legal obligations.
Microsoft recently said it may move to hold onto only identifiable data for six months. Google retains identifiable data for nine months.
The European Commission wants a six month limit for identifiable data held.
The UK government has so far resisted introducing a planned law to store the electronic communications records of every UK citizen. The plan did not make it into the Queen's Speech this month.