How Google Works: A Complete Guide to the Search Engine

Google processes more than 8.5 billion queries every day. Each time a user types a question into the search bar, Google must — in under a second — scan an index of hundreds of billions of web pages, assess their relevance, and sort the results in a logical order. How is that possible? And more importantly, what do we need to understand about this mechanism to rank our sites better?

The Crawler: the First Step in Indexation

Before Google can display a result, it must first discover the pages that exist on the web. That's the role of Googlebot, Google's robot program (or "crawler").

Googlebot follows links: it starts from pages it already knows, visits every link it finds there, and so on — a continuous depth-first and breadth-first exploration of the web. This process never stops. Google re-crawls known pages regularly to detect updates, and constantly discovers new pages through incoming links.

To help Google discover your content quickly, you can:

• Submit an XML sitemap via Google Search Console — it's a map of your site Google can consult directly
• Earn inbound links from already-indexed sites — the fastest signal for a page to get discovered
• Avoid blocking important resources in your robots.txt file on pages you want indexed

A common mistake: accidentally blocking critical resources (CSS stylesheets, JavaScript) in robots.txt, which can prevent Google from rendering your page properly and evaluating its content.

The Index: Google's Massive Database

Once a page is crawled, Google analyzes it and, if it meets its criteria, adds it to its index — a gigantic database cataloguing the words and entities present in each page, with billions of entries.

This indexation phase is critical. A non-indexed page simply doesn't exist for Google, regardless of how great its content is. Several reasons can prevent indexation:

• A <meta name="robots" content="noindex"> tag on the page
• An HTTP 404 (not found) or 5xx (server error) response code
• Duplicate content — Google may decide to index only one version
• Low-quality content — Google may judge that a page doesn't provide enough value

You can check whether your pages are indexed via the URL Inspection tool in Google Search Console. It's a reflex every SEO professional should develop.

The Algorithm: How Google Ranks Pages

Indexation is necessary. But Google doesn't display every indexed page for a given query — it sorts them. This is where the ranking algorithm, the true core of SEO, comes in.

Google uses over 200 known ranking factors (and many more undisclosed ones). Here are the most decisive:

Semantic Relevance

Google no longer simply looks for exact keywords on a page. Since the BERT (2019) and MUM (2021) updates, it understands the meaning of queries and answers. It can connect "how to lose weight" with a page that talks about "nutritional strategy for slimming" even if the exact words don't match.

For you, this means keywords still matter, but content must above all precisely address the user's intent.

Authority (PageRank and Link Building)

Google's original idea, born with PageRank in 1998, remains at the heart of the algorithm: a link to your page from another page is a vote of confidence. The more quality links you have, the higher your authority rises.

But this mechanism has become more sophisticated. Google now analyzes:

• The quality of the linking site (a link from a national news outlet is worth infinitely more than a generic directory)
• Topical relevance of the source site (a link from a competing or complementary site in your niche carries more weight)
• The anchor text — the clickable text — which gives a semantic signal about the subject of your page

Core Web Vitals and User Experience

Since 2021, Google has officially incorporated user experience metrics into its algorithm. The three main ones are:

• LCP (Largest Contentful Paint): loading time of the largest visible element — should be under 2.5 seconds
• INP (Interaction to Next Paint): responsiveness to user interactions
• CLS (Cumulative Layout Shift): visual stability of the page (no elements shifting during load)

A technically solid site won't be penalised, but one with very poor scores can be disadvantaged compared to equivalent competitors.

E-E-A-T: Experience, Expertise, Authority, Trust

Google evaluates the credibility of the author and the site, especially for sensitive topics (health, finance, law). The acronym E-E-A-T — Experience, Expertise, Authority, Trust — summarises the qualitative criteria that influence how Google's "quality raters" evaluate pages.

This isn't a direct algorithmic factor, but it indirectly influences rankings through content quality assessed by humans, which itself serves to calibrate the algorithm.

The SERPs: What You See in Results

Search Engine Result Pages (SERPs) have evolved dramatically. Today, a results page can contain:

• Classic organic results — the blue links we've known since the beginning
• Knowledge Panel — a structured information box about a known entity
• Featured Snippet — a direct answer extracted from a page and displayed in position 0
• Google Maps / Local Pack — for searches with local intent
• Image Pack, Video Pack — for queries that lend themselves to it
• People Also Ask — related questions with accordion answers
• AI Overview (formerly SGE) — an AI-generated answer at the top, increasingly present

Since the rollout of AI Overviews in 2024, position 1 organic has lost some of its visibility. Some informational queries are now resolved directly by Google's AI, without a click through to any site. This is one of the reasons why AI search and GEO is becoming a complementary issue to classic SEO.

Algorithm Updates

Google updates its algorithm thousands of times a year — most discreetly. But regularly, major Core Updates cause significant reshuffles in rankings. In 2023-2024, the Helpful Content Updates notably penalised sites with low-value content (generated en masse by AI without human verification).

Update categories to watch:

• Core Updates (quarterly): general reweighting of signals
• Spam Updates: targeting spam techniques (artificial links, cloaking)
• Helpful Content System: valuing human, useful content written first for people

The best strategy for weathering updates? Build a site whose content is genuinely useful and deserves its position — what SEOs sometimes call "white hat SEO."

What This Changes for Your SEO Strategy

Understanding how Google works leads to better decisions:

1. Don't fixate on exact keywords but on intent and topic
2. Invest in deep content rather than many shallow articles
3. Build links naturally rather than paying dubious networks
4. Optimise technically to facilitate crawl and indexation
5. Monitor Core Updates to understand algorithmic evolution

The best way to put all this into practice? Simulate real SEO decisions in our SEO simulation game, which confronts you with concrete choices week after week. You can also deepen the theory with our guide to learning SEO.

Ready to Understand Your Current Rankings?

If you want to know where your site really stands in terms of these mechanisms — whether that's crawl, indexation, authority, or user experience — an SEO audit is the best starting point. It precisely identifies the obstacles and opportunities specific to your situation.

---

Article written by Alexandre De Sousa, SEO & GEO consultant, founder of iZZi. Last updated: May 2026.