Definition:
A metasearch engine is a system that sends the same query to several search engines or information sources and brings their responses together on one page. Before displaying them, it may standardise formats, remove duplicates and apply its own ranking criteria.
Unlike a conventional search engine, it does not normally discover and index all the information it searches by itself. It relies on external indexes, APIs, catalogues or feeds, although it may store temporary data and add its own processing layer.
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How a metasearch engine works
When someone enters a query, the metasearch engine adapts it to its connected sources and sends several requests. It then receives responses built with different formats and criteria. The system has to identify matches, merge repeated results and decide where each item should appear in the final list.
This process is not always visible to the user. Some tools show the source of each result, while others present a single combined list. Coverage and speed depend on the available sources, their technical limits and how quickly they respond.
MetaCrawler, developed at the University of Washington in 1995, was one of the earliest well-known examples. Its purpose was to query several search engines and combine their results instead of building a general index with its own crawler.
Types and examples of metasearch engines
The model is used in general web search and in specialised services. They do not all work in the same way, and some combine metasearch, proprietary databases and direct agreements with providers:
- General web search: Dogpile, MetaCrawler and WebCrawler bring together results obtained from other search services.
- Private search: Startpage acts as an intermediary to provide external results without building a personal search profile.
- Travel and accommodation: Trivago, Kayak and Skyscanner compare offers obtained from airlines, hotels, agencies and booking platforms.
- Jobs and classified listings: Jooble, Indeed and Trovit aggregate offers from different portals, although their operation also resembles that of a vertical search engine.
Booking.com is not, by itself, a hotel metasearch engine: it operates primarily as an online travel agency. Similarly, a comparison service that allows bookings to be completed on its own platform may combine aggregation, intermediation and sales functions.
Advantages and limitations
Consulting several sources through one interface saves users from repeating a search and may increase the variety of responses. It also supports comparisons of prices, availability or conditions when the data comes from different providers.
Wider coverage does not guarantee complete information or better ordering. A metasearch engine depends on what its sources provide, may introduce delays and has to resolve differences between formats. Duplicate removal is not perfect either. The final order may also be influenced by commercial agreements, advertising or affiliate commissions.
For these reasons, the position obtained in an original SERP does not necessarily remain the same in a combined list. Each metasearch engine may apply additional filters and criteria.
Differences between a search engine and a metasearch engine
A web search engine crawls documents, processes them through indexing and answers queries from its own index. A metasearch engine delegates much of that retrieval to other systems and works with the responses it receives.
The boundary is not always absolute. Vertical services may maintain proprietary databases, receive inventories directly from partners and query external sources at the same time. What defines a metasearch engine is that an essential part of its response comes from combining results generated by other systems.