Like any search engine, Google works thanks to what are known as crawler bots — also called spiders or crawlers. They explore the web by simply following links. When they discover a link, they follow it, and so on, until they have traversed the entire web. There is not just one crawler, but millions — along with specific bots dedicated to images, mobile content and much more.
Crawl, then indexation
When a document is crawled, Google applies a decision tree to determine whether or not the page should be indexed. We speak of “indexation” because Google will place the document into its vast library, where it catalogues the web.
Indexation, then ranking
A document that is indexed does not mean it will rank for a keyword in search results — let alone on the first page of Google.
However, being indexed means it is eligible to rank.
If it has been crawled but not indexed (easily visible in Google Search Console), it will be impossible for that page to appear on Google.
To summarize, Google works as follows:
- It discovers your page (crawl)
- It decides whether your page is relevant enough to include in its database (indexation)
- It decides based on various criteria whether your page is eligible to rank in search results (ranking)
If you want to know exactly how bots work for crawling and indexation (and how to optimize for them), head to the dedicated chapter on indexation.
Crawl and indexation SEO optimization falls under what is known as technical SEO.
Note: The word SEO stands for Search Engine Optimization — simply the process of optimizing a site or page to rank better in search results.
How Google classically works
As shown in this image from a Google patent, this diagram illustrates everything that happens on the surface.
How to appear in Google’s search results?
As seen above, it all starts with crawling. Google must first find your page.
If no site links to any of your pages and you haven’t submitted your site to Google Search Console via a sitemap.xml, Google has no way of knowing your site exists. That’s where you need to start.
Next, if your page is sufficiently relevant and is not duplicated from another site or another page on your own site, Google will generally index it in its database.
Finally, if your page provides additional value compared to other pages on Google, it has the potential to rank prominently. If you add nothing beyond what already exists, Google has no reason to position you on the first pages of search results.
Google’s ranking factors
First, no ranking factor is identical for every topic, theme or keyword.
This is due to the Learning to Rank algorithm (one of Google’s sub-systems). This algorithm weights each factor — and those factors vary depending on the nature of your query.
For example, content freshness plays a more important role for a breaking news topic than for a dictionary definition. Another example: the textual content of a product page on an e-commerce site has almost no impact, since everyone sells the same product.
So the ranking criteria are not always the same — and even the criteria that are always present don’t carry the same weight depending on context.
If you want to know all the important Google algorithms, you’ll find them here.
But to answer the question about ranking factors, here is a very simplified summary:
- Good quality, relevant content aligned with the user experience (search intent)
- Links pointing to your pages (from external sites and between your own pages)
If you want to learn more, read our comprehensive article on Google’s ranking factors — or our article on the Google Leaks!