A competition for software testers to reveal bugs in major search engines has unearthed over 600 in Google, Google Caffeine, Bing and Yahoo.
The Battle of the Search Engines, as it is known, was carried out by uTest, which uses crowdsourcing to test software.
Over 1,100 software professionals from over 50 countries took part in uTest's Battle of the Search Engines.
Of the 600 bugs found, about 78 were said to be "show stoppers" - or very serious flaws.
Google had 130 bugs, with 8% show stoppers, Bing had 321 bugs, of which 14% were showstoppers, and Yahoo had 70 bugs, with 10% showstoppers, said the report.
The project measured the accuracy of search results, speed, real-time relevance and overall usability of the websites. Google was seen as the best in every category.
But it also revealed that 30% of software professionals were "favourably surprised" by Microsoft Bing's and 10% want it as their default search engine.