Imagine a vast library, filled with knowledge. However, when compared to a traditional library, this one makes its decision on which books belong on the shelves and which ones should be kept in the dusty corners by using complex algorithms. This is the basic concept underlying Google's multi-layered indexing method, in which a website's discoverability is mostly determined by its quality.

The Complication of Indexing and Crawling

Let's examine the first stages before moving into the quality check. Google's endless web crawlers search the internet continuously, discovering new web sites by following links that act as breadcrumbs. The data is then sent back to Google's indexing engine by these crawlers. 

The Spotlight on Quality: Filtering the Information Stream

Indexing isn't a simple act of storing every discovered page. Google meticulously evaluates each page to ensure it meets specific quality criteria.  This quality check acts as a filter, ensuring only the most relevant and valuable content gets stored in Google's vast index, the library's virtual shelves.

So, When Exactly Does the Quality Check Happen?

There isn't a single, definitive moment during which Google assesses quality.  It's more like an ongoing evaluation throughout the indexing process. Here's a breakdown of the key phases:

Initial Crawling: When a web crawler first encounters a page, it gathers basic information like title tags, meta descriptions, and content structure. This initial analysis provides clues about the potential quality of the content.

In-Depth Analysis: Once the basic information is collected, Google's algorithms delve deeper. They examine things like the overall user experience, mobile friendliness, freshness, and relevancy of the information.

Algorithmic Judgment: Based on a number of different parameters, Google's advanced algorithms determine the "quality score" for the page. This score affects the page's indexing quality and its visibility in search results.

This is Not a One-Time Test; It's an Ongoing Evaluation

There is more than one pass/fail test in the quality check. Google's algorithms keep an eye on all indexed websites, constantly.  A website's quality score can improve in response to significant content or user experience improvements, which can improve search engine ranking.  On the other hand, a website's quality score might significantly decline if it starts to look outdated, irrelevant, or filled with spam, which could result in removal of or reduced search exposure.

Beyond Algorithms: Human Experience Is Important too

Although algorithms are important, Google also uses the opinion of humans to assess quality.  To make sure search results live up to user expectations and Google's standards, a team of quality raters examines the results.