Wikipedia
SafeSearch is a feature of Google Search that acts as an automated filter of pornography and potentially offensive content.
A 2003 report by Harvard Law School's Berkman Center for Internet & Society stated that SafeSearch excluded many innocuous websites from search-result listings, including ones created by the White House, IBM, the American Library Association and Liz Claiborne. On the other hand, many pornographic images slip through the filter, even when "innocent" search terms are entered. Blacklisting certain search terms is hindered by homographs (e.g., " beaver"), blacklisting certain URLs is rendered ineffective by the changing URLs of porn sites, and software to tag images with copious amounts of flesh tones as pornographic content is problematic because there are a variety of skin tones and pictures of babies tend to have a lot of flesh tones. Google's ability to filter porn has been an important factor in its relationship with the People's Republic of China.
On 11 November 2009 Google introduced SafeSearch Lock, which allows users with Google accounts to lock on the "High" mode of SafeSearch in Google's Web, image and video searches. Once configured, the user can log out of their Google account and the setting will stick to prevent any change to the filtering level.
On 12 December 2012 Google removed the option to turn off the filter entirely, requiring users to enter more specific search queries to access adult content But this happens only to English sites and non-English users are still required to be careful with their local language search as Google is not filtering most of the adult contents even with safe search on and with specific keywords.