However, there have been no major concerns. Types of search engines By source Desktop search Federated search Human search engine Metasearch engine Multisearch Search aggregator Web search engine By content type Audio search engine Full text search Image search Video search engine By interface Incremental search Instant answer Semantic search Selection-based search Voice Search By topic Bibliographic database Enterprise search Medical literature retrieval Vertical search See also Automatic summarization Emanuel Goldberg (inventor of early search engine) Index (search engine) Inverted index List of search engines Search as a service Search engine optimization Search suggest drop-down list Solver (computer science) Spamdexing SQL Text mining References Information retrieval systems