Search engine robots, which are also known as crawlers, spiders, or bots, are automated programs that are built for the purpose of discovering, indexing, and ranking content on the internet. This process is complex and continuous, and it’s what makes it possible for a search engine to provide relevant search results in a fraction of a second. The process has three main parts; crawling, indexing and ranking.
Crawling
Crawling is the process where the robots scour the internet looking for new or updated web pages. They start with a list of known URLs, called “seed URLs”, and systematically follow the links on those pages to find new ones.
How it works:
- A robot, like Googlebot, visits a URL it is aware of
- It downloads the text, images, and videos on the page
- It looks for any links on the page (both internal and external) and adds them to its queue of pages to visit.
- This process creates a massive network, allowing the crawler to discover billions of pages.
Crawlers are designed so that they don’t overload a website’s server with requests. Website owners can also control how a search engine robot interacts with their site using a robots.txt file, which tells the crawler which pages it is or is not allowed to visit.
Indexing
Once a page is crawled, the search engine analyzes the content and stores the information in its index, which is a massive database. The index is a massive repository of all the content it has found on the web.
How it works:
- The crawler sends the page’s data to the search engine’s indexing system.
- The indexer processes the content, analyzing text, images, video files, and metadata (page title, descriptions, etc.).
- It categorizes the information and associates keywords and other data points with the page. This is what allows the search engine to match a user’s query to a specific page.
- Not every page is indexed. Search engines have quality algorithms that determine whether a page is worth including in the index. Low-quality, low content, or duplicate pages may be excluded.
Ranking
Ranking is the final step in the process where the search engine’s algorithm determines the order in which indexed pages are displayed in response to a searcher’s query. The search engine’s goal is to provide the most relevant, helpful, and high-quality results at the top of the search results page.
How it works:
- When a user types a query (e.g., “how to qualify for a mortgage), the search engine’s algorithm instantly searches its index for all pages that are considered a match.
- The search engine applies hundreds of factors to rank website pages. Some of the factors include:
- Relevance: How well the page’s content matches the user’s query.
- Authority: The credibility and trustworthiness of the website (often determined by the number and quality of other sites that link to it).
- User Signals: How users have interacted with the page in the past.
- Usability: Factors like page speed, mobile-friendliness, and a secure connection.
- Freshness: How recently the content was published or updated.
Searches are NOT done live when you enter a query
Search engines don’t actually search the internet “live” when you enter a search query. Instead, they search their pre-built index, which is why they can provide results in seconds. The constant crawling and indexing process keeps this index up-to-date.
The purpose of doing SEO is to make sure your website and the content on its’ pages are search engine friendly. The easier it is for search engines to crawl, index and rank your websites URLs, the more traffic and conversions you are likely to get.