A search algorithm is a set of rules and methods used by search engines to retrieve relevant information from the Web in response to a user query. These algorithms are at the heart of how search engines like Google, Bing and DuckDuckGo work. Here’s how these algorithms generally work:

1. Crawling the Web

Search engines use programs called crawlers or bots to crawl the Web, following links from one page to the next. They collect data from the web pages they visit, store it and index it. This process creates a copy of the web pages available on the Internet, called an index.

2. Indexing

After crawling, the collected web pages are indexed. The index is a huge database containing all the information gathered by the crawlers. During indexing, search engines analyze the content of pages to understand their subject matter, relevance and key terms. In this way, they create a map of all the data for easy retrieval at a later date.

3. Search and Ranking

• When a user types a query into a search engine, the algorithm searches the index for the pages most relevant to the keywords in the query. This search is followed by a ranking of the results according to various criteria.
• Search engines use complex algorithms to determine the order of results (SERP – Search Engine Results Page). These algorithms take many factors into account, including :
  • Keyword relevance: correspondence between query terms and indexed page content.
  • Page authority: determined by the number and quality of backlinks.
  • User experience: page quality in terms of loading time, mobile adaptability, structure, etc.
  • Search context and history: sometimes results are tailored to the user’s history or location.

4. Custom settings

Search engines also use algorithms to personalize search results according to the user, taking into account their search history, preferences, geographical location, etc.

5. Machine learning

Modern search engines use machine learning techniques to refine their algorithms. For example, Google uses algorithms such as RankBrain, which is a component of their main search algorithm (Hummingbird). RankBrain helps Google to better interpret ambiguous or complex queries and deliver more relevant results by learning from past user interactions.

In short, in the context of online search engines, a search algorithm is a sophisticated system that combines crawling, indexing, search, ranking and machine learning techniques to deliver the most relevant results in response to a user query.