All4one started in 1996 as a parallel search engine. It was developed by John E Haag. A search query was sent to the four search engines Yahoo, Lycos, Alta Vista and WebCrawler at the same time. On the All4one results page, the results pages of the four search engines were displayed side by side in frames, which the user could then compare with each other. All4one was discontinued in 2002.

From 2000 to 2002, All4one offered various thematic searches: A business, high-tech, entertainment and sports news search. According to the website, four thematic search engines were also searched here, whose result pages were displayed next to each other in frames.