How Google Crawls and Indexes the Web

Have you ever wondered how Google works? How Google crawls and indexes the Web? Why do some pages rank higher than others? What is the magical combination of keywords and quality content to make your website appear on the first page of search engine results?

All of these factors determine how effective your search engine optimization really is. Google is able to generate quality search results to users within a split second of them typing in a query.

Google has indexed more than 40 billion websites, according to an infographic from Quicksprout. In comparison, Bing has only indexed 14 billion pages.

Indexing is similar to the reference section in the back of a textbook, only on a much larger scale.

This means the search engine has a record of all the pages it has crawled and cached.

Google crawls pages to make a list of all the words on a website, which is how it delivers relevant content when people search for something. The search engine can index information from key content tags like title and ALT tags. However, it can't process all rich media files or dynamic pages.

Indexing ensures Google users find more relevant results based on context. Google gives the example of searching for dogs. A user would probably want photos or information about a specific breed, rather than a page that used the word dog many times. This reflects many of the changes in SEO in the last few years.

Stuffing a Landing Page is no longer an acceptable way to drive traffic. Google gives higher rankings to sites that supply searchers with valuable information.The search engine also prioritizes information that has been recently updated to ensure users find relevant results.

How Does Google Crawl Pages?

Indexing can't happen without a critical step in the process: crawling. Google does this with software, including Googlebots.

The crawlers follow links and scan through information on Web pages, similar to what a human would do, only much quicker and more in-depth. These crawlers attempt to scan and index every page on the Web, although currently only 10 percent of all websites are indexed.

Typically, the crawling process starts from a sitemap that website owners provide the search engine. Google has programs with algorithms that determine how often sites need to be crawled and which pages to fetch from the site. This ensures the index is up to date with new websites, changes to existing websites and dead links.

Depending on the frequency that Google's algorithms determine, crawls can occur anywhere between several times per day or once every six months.

What Happens When Google Can't Crawl a Page?

There are a number of reasons Googlebots may not be able to crawl your website, such as an incorrectly configured Robots.txt file. These files prevent crawlers from accessing certain pages on the website.

Some small-business websites end up with only some pages indexed and everything else blocked, as Quicksprout pointed out.

Most websites do not need to block certain pages, but site owners can do this on a granular level. Instead of blocking particular pages, Robot.txt is intended to give Google crawlers more specific instructions for how to read the page.

In addition, poorly formatted title, meta and author tags can prevent Googlebots from being able to read the website. If you switch to a new domain or site-hosting service, a poorly configured .htaccess file can get in the way of crawling.

The same thing happens with URL parameters, although this mistake can cause Google to drop a website from its index entirely. The search engine will also penalize domains with a bad history, such as link farms. Low page ranks won't attract very much attention from Googlebots. Poor servers or hosting services can prevent crawlers from accessing the page, as well.

To ensure your Web pages are crawled, it's important to take the steps to address these issues. Google's Webmaster tools allow site owners to determine where specific crawl errors are happening.

Ensuring the Robot.txt file is correctly configured is crucial.

In addition, adding a complete and up-to-date site map makes it easier for Googlebots to crawl your website. Webmaster tools can help create this as well.

How This Works in Search

If you want to improve your page rank, Google has to crawl and index your website. The search engine gives some tips on how to do this effectively:

• A website structure should have a clear hierarchy with text links. Each landing page should be accessible from at least one static text link
• Limit the number of links on one page.
• Provide a site map for visitors with links to the most important pages. Consider splitting it into sub-categories for websites with a high number of links.
• Think of the words potential customers would use to find your website and include those terms and phrases on your landing pages.
• Use text instead of images for important names, information and links because crawlers don't recognize text within an image. If this is unavoidable, be sure to use an ALT tag with descriptive text so pages can still be crawled.
• Be vigilant about broken links and HTML errors

Ultimately, search engine results are generated based on what Google expects the user will find most helpful. Putting yourself in the mindset of a potential visitor can help you get it right. Google factors in a number of other ranking signals that determine where a website shows up in the results, but user experience and relevant content are two of the most important aspects.

Google also bases its ranking on how many inbound links a page has from other websites because it indicates that there is content worth sharing. However, the caveat to this ranking signal is they have to be quality links. The search engine proactively seeks out and removes spammy links.

Optimizing your website for search is often complicated, but a necessary undertaking for increasing your visibility on the Web.