How Google discovers pages (crawling) in SEO Fundamentals - Step-by-Step Explanation

Introduction

Imagine trying to find every book in a huge library without a catalog. Google faces a similar challenge when it wants to find all the pages on the internet. It needs a way to explore and find new or updated pages so it can show them in search results.

Explanation

Starting with Known Pages

Google begins crawling from a list of known web pages, often popular or previously discovered sites. These pages act like starting points or seeds for the crawling process. From these seeds, Google looks for links to other pages to explore next.

Google starts crawling from a set of known pages to find more pages through links.

Following Links to Discover New Pages

When Google visits a page, it reads the links on that page to find other pages. These links act like paths leading to new content. By following links from page to page, Google can discover a vast network of web pages across the internet.

Google discovers new pages by following links found on already known pages.

Respecting Crawl Rules

Websites can tell Google which pages to crawl or avoid using special files like robots.txt or meta tags. Google respects these rules to avoid crawling pages that site owners want to keep private or unindexed. This helps Google focus on useful content.

Google follows website rules to decide which pages it can or cannot crawl.

Handling Updates and Changes

Google revisits pages regularly to check for updates or new content. It prioritizes pages that change often or are important. This way, Google keeps its index fresh and shows the latest information in search results.

Google revisits pages to keep its information up to date.

Real World Analogy

Imagine a mail carrier delivering letters in a neighborhood. They start with a list of houses they know, then follow paths and streets to find new houses. Some houses have signs saying 'No mail,' so the carrier skips those. The carrier also revisits houses that often change their mailboxes.

Starting with Known Pages → Mail carrier's initial list of houses to deliver mail

Following Links to Discover New Pages → Mail carrier following streets and paths to find more houses

Respecting Crawl Rules → Houses with 'No mail' signs that the carrier must skip

Handling Updates and Changes → Carrier revisiting houses that frequently change their mailboxes

Diagram

Diagram

┌───────────────┐
│ Known Pages   │
└──────┬────────┘
       │
       ▼
┌───────────────┐      ┌───────────────┐
│ Page A        │─────▶│ Page B        │
│ (Links to B)  │      │ (Links to C)  │
└──────┬────────┘      └──────┬────────┘
       │                      │
       ▼                      ▼
┌───────────────┐      ┌───────────────┐
│ Page C        │      │ robots.txt    │
│ (New Page)    │      │ blocks Page D │
└───────────────┘      └───────────────┘

Diagram showing Google starting from known pages, following links to discover new pages, and respecting crawl rules like robots.txt.

Key Facts

Crawling → The process Google uses to visit web pages and find new or updated content.

Seed Pages → Initial known web pages from which Google starts crawling.

robots.txt → A file websites use to tell Google which pages not to crawl.

Links → Paths on web pages that Google follows to discover other pages.

Recrawling → Google revisiting pages to check for updates or changes.

Common Confusions

Google crawls every page on the internet instantly.

Google crawls every page on the internet instantly. Google crawls pages over time, starting from known pages and following links; it cannot crawl the entire internet instantly.

If a page is linked, Google will always index it.

If a page is linked, Google will always index it. Even if a page is linked, Google may not index it if the site blocks crawling or if the page has noindex tags.

Summary

Google discovers web pages by starting from known pages and following links to new pages.

Websites can control crawling using rules like robots.txt to block certain pages.

Google revisits pages regularly to keep its search results up to date.