Currently there are hundreds of search engines operating on the internet. These range from the well known general search engines to a number of niche search engines that specialise in specific types of content, particular methods of searching or just provide a unique interface to the similar results. Wikipedia has a good list of available search engines.

Despite the number of search engines, Google and Yahoo! are the truly dominant players. Google has a market share of between 75-80% globally and Yahoo! between 8-10% globally (As at Apr 2009). Some countries have local search engines that have a dominant position within that country however.

Because Google towers over the other search engines in terms of usage, including its nearest rival Yahoo!, optimisation is often a byword for getting better search engine ranking in Google and ignoring the rest. Whilst this can often make a lot of sense, if you have specialist content you may be able to find a search engine that specialises in the content your website is presenting. These search engines can generate very high quality traffic, namely people that are especially interested in your content. If you are targeting a specific geographical location there are other search engines that may have greater market share for specific countries or localities your require. It should also be considered that there is a lot of competition trying to optimise sites for the Google search algorithms. Other search engines, although having much less traffic, may be easier to obtain a higher search ranking.