Web Crawling: What Are Search Engines? (+What Is a Site Browser & Web Crawler Definition)

on SEO June 03rd, 2021

The digital revolution has been a major turning point in human history. This information age has completely changed the way we work, study, play, and socialize, plus it’s having unmeasurable effects on real-life society. But, not many people are aware that web crawling is the process that keeps the entire ecosystem active. And, while there are many SEO companies out there, you need to work with a team of specialists that truly understands how web crawlers impact your search engine rankings.

Web crawling has made a near-infinite amount of data and information available, which can be leveraged by an infinite number of companies across the world.

Free search platforms like Google have led the charge of the digital revolution, providing free and easy access to data on the internet, and these engines’ main tool in doing so is a software called web crawlers. In a nutshell, web crawlers are responsible for rounding up online content and data for search engines to parse and organize.

At Fannit, we have spent the last decade working on developing SEO strategies for clients in different industries.

We know just how important search engines are for any marketing strategy, and we could not get here if we had not taken the time to understand software like web crawlers.

So, let us share our knowledge of crawling and how you can make sure that your website is easy for web crawlers to find and read.

What Is Web Crawling and What Are Web Crawlers?

But what is a web crawler? How exactly do these software help search engines organize and filter the entire internet? How do we define web crawlers?

First, a web crawler is a type of program that’s also called a spider, crawler bot, or simply a bot. Crawlers are used by search engines to read and organize the contents of every single page of every single website on the internet. These programs essentially feed search engines all the information they need to create a giant database.

A web crawler is a type of software that acts on behalf of search engines, so each platform has developed one or more unique spiders. Just like they sound, these programs read every single part of your site line by line. Having a logical site structure and developing unique content for each page can help crawlers understand your site.

Every time a crawler comes across a site, it then starts to learn everything it can about the page’s data.

Web crawlers work hard and try to do this for as many pages on the web as possible.

Once a web page is known to the crawler tool, the web crawling software indexes it along with the others, making sure the data is known and easy to find for a search engine.


The Relationship Between Web Crawlers and Search Engines

When you type a search term into Google or another free search engine tool, it will present you with a list of relevant results.

However, it would not have known this information and data wouldn’t be readily available if it was not for its web crawler trawling through the world wide web and sorting it into easy-to-find categories. Web crawling software allows search engines to get a user’s results as efficiently as possible.

You may have known about them under a different name.

Again, crawlers are often called spiders, robots, or bots, and it sums up nicely exactly what they do: automatically crawl through the world wide web, in a process that sorts sites out into different categories based on their available information and data. So, the crawler can then index each site properly, all while making the data known to the crawlers’ search engine.

Have you ever color-coded your filing cabinet to make it simpler and faster to get relevant files? Or perhaps used the Dewey decimal system to help get a book at the library, amongst a huge number of shelves? A web crawler program is the digital search engine’s equivalent to physical data sorting systems.

How Do Web Crawlers Work?

Sifting through the reams and reams of data and millions of pages on the internet is certainly no small feat.

On top of this new websites are being designed and uploaded all the time, which means more new data is being created every day that isn’t yet known to a search engine.

There may have been a brand new website launched as you read this paragraph! So how does a crawler program manage to undertake the seemingly gargantuan task to get and download all this data?


First of all, they start with a list of already known and reliable websites and URLs whose data they have already finished categorizing and indexing, also known as a ‘seed’.

The web crawler then looks for links on these pages and follows them through, so they can get to new websites for them to index and sort their data for the crawlers’ search engines.


The web crawler will then scan each page it visits, recoding all the information and data.

It scans this data for a number of factors such as keywords, which gives the bot insight into which categories it should index each page.

This is how a keyword search on Google ends up with a list of relevant websites for the user.

Web crawlers or bots then repeat this process, going from link to link, recording information and data from each site.

If you’ve ever used Wikipedia then you will probably be able to relate to what web crawling is! Of course, as anyone who’s ever used the internet knows, there are countless links on every website, so this process of crawling for data through each one could easily go on forever.

Categorizing and indexing the data for all the websites and each and every page on the internet would require a massive amount of time, even for the fastest web crawler.

Without proper guidance, web crawling could easily get bogged down amongst the millions and millions of web pages, much of which might not have relevant or useful data, thus leading to poor results for search engine users.


This is why a bit of targeting can go a long way.

Free search engines use algorithms for web crawling, giving crawlers a specific set of instructions and conditions for choosing which links to follow, and which to ignore.

They also control a number of other factors, such as how long to crawl each page and how often crawlers should check back to see if there have been any updates or changes to the page data.

Remember, the websites that a crawler’s algorithm deems important enough to spend a lengthy amount of time on the page, and for frequent revisiting to check for updates, will also be ranked highly by Google itself.

The more your website appeals to a crawler the higher up it will appear in Google’s search results.

Let’s take a look at the different factors web crawlers and bots consider when crawling for data.

How Important is the Website?

First of all, a crawler needs to check if a website is important and authoritative. Some pages and websites have more reliable data than others after all.

This is why crawlers do not sort through every single page on the internet and also, just do not need to. But how is a crawler able to tell which ones are reliable, ample sources of information, and which sites are duds?

There are a number of markers that can give away a website’s importance to crawlers.

These may be based on how many backlinks to it from other pages there are, the amount of traffic the site receives, and anything else the algorithm coder deems to be important.

All these together mean that the sites a crawler indexes for its search engine and is more likely to be authoritative, contain high-quality data and information, and be useful for search engine users.

These are the sites that a crawler will prioritize and are likely to find themselves at the top of the search results.

How Often Should a Website Be Crawled?

As we mentioned before, the internet is constantly changing with websites being updated and data edited every day, as well as the creation of new websites.

If a search engine wants to continue to provide relevant and useful information to its users, it needs to constantly monitor websites for any changes which might affect their indexing.

The importance of the website is also a crucial factor in deciding how often a web crawler should revisit a page.

Authoritative and reliable pages are likely to have the best and most up-to-date information, so a web crawler will want to keep checking back.

What Are a Web Crawler’s Robots.txt Requirements?

One way that a web crawler makes a choice about what page to the index is by using something called a robots.txt file.

A robots.txt is a file hosted by the target page and includes certain rules for any visiting crawler to that website. The robots.txt requirements dictate what pages it allows a spider to crawl and if it allows them to follow a certain link or not.

Here’s how search engines use robots.txt files. If there is no robotx.txt file, then the spider will proceed to crawl your website as normal, as you have not stipulated any restrictions.

If there is a robots.txt file then of course it will follow any instructions on there. However, if your robots.txt has errors within it then a web crawler will not crawl that website, so it will not be indexed.

Why Do Some Pages Use a Robots.txt File?

So why do some web pages use a robots.txt file that allows what a web crawler can and cannot do on their site? There are many reasons they may consider when writing the robots.txt file and deciding if you want a spider to crawl your page, based on factors such as server resources and page relevance.

Do You Have Enough Server Resources?

First of all, whenever someone accesses a website they create requests that the web server has to respond to. This uses the server’s resources. It’s no different for a bot.

When a bot tries to crawl a website to index it, it also sends a request to the server to download data, using its resources.

For some servers who do not have the bandwidth to cope with multiple requests at once, it may be wise for them to deny web crawling on their site.

Otherwise, it could cause the server to drastically slow down, crash, or drive up bandwidth costs as crawlers attempt to download too much data at once.

Restricting Access to Irrelevant or Confidential Web Pages

There could also be pages and data on a website that the website owners do not want the crawler to have access to.

Perhaps it could be because they have their own search function on the site, and don’t want all of their internal search results to end up on the search engine’s results page, as this would be of no use to any users.

Maybe they currently have an ongoing marketing campaign, such as a discount voucher, and only want to direct certain people onto a specific page for the discount.

They wouldn’t then want just anyone turning up on the discount page because it showed up on a search engine, so they would bar crawling to this page.

Making Efficient Use of a Web Crawler’s Time

Another point is that a search engine’s crawler and bots have their own set of instructions on what pages to search, what sites to revisit, and importantly for robots.txt, how long to crawl it.

This is important because a crawler has a set URL budget, which dictates how long they should spend crawling a particular site in order to save resources.

You, therefore, want to make sure that a web crawler does not waste its allocated time on your website crawling through irrelevant pages you do not need to be seen.

Robots.txt files can help here, by directing crawlers to the pages you do want to turn up on a search engine results page so their time is well spent crawling the right pages on your website.

To sum up, web crawlers assist search engines in doing the following:

Site Crawling

First of all, they crawl online for the content, data, and information search engines need, scouring each site’s HTML code and the content on it.


Once the online web content and data have been found, the web crawler will index it into different categories based on content, making it readily available to show up at the next relevant query.


Not only do they rate URLs based on what information they contain for different categories, but a crawler also advises on how highly they should be ranked, based on relevance, quality, user experience, and more.

How Can Web Crawling Help Your SEO (Search Engine Optimization)?

We’ve discussed what web crawlers, bots, or spiders, are and how they work.

But why do we, as marketers, need to know about them?

The reason is that a better understanding of how these bots work will give you insight into how to improve your website’s SEO, pushing it up the search results rankings.

So how can you use a web crawler Google strategy to boost your SEO?

Manage Your Robots.txt Restrictions

First of all, remember the robots.txt file. While some people use robots.txt to block crawlers from crawling and indexing their page if you want to improve your SEO make sure you do not do this.

If a web crawler can’t search your page and index it, it will not even show up in the search engine’s results, where no one will find it.

Therefore, when writing your website’s robots.txt file, make sure that all the pages you want to be found are actually accessible to web crawling.

This will ensure they will all be properly searched and indexed, giving them a chance to appear on the search engine’s results page.

Don’t Forget About a Web Crawler’s Own Restrictions

Remember, restrictions aren’t just placed by those hosting a server. The owners of a crawler also use restrictions to make sure they only crawl the most relevant pages and don’t get bogged down in the millions of irrelevant ones.

Google for example restricts its bots in: what pages to scan, how often to crawl, and how much pressure to put on a server.

Let’s look back at the factors that web crawler’s algorithms take into account when deciding what sites to crawl.

The first one was a site’s importance, in order to select the most authoritative pages for its search result rankings.

One way it rates a site’s importance is through how many links to it there are from other websites.

Do Your Backlink Outreach

This is why it’s so helpful for your SEO to get as many backlinks to your URLs out there as possible.

There are a few ways you can do this, such as pushing out online content that has links within the text or images. Investing in some PR can help with this, as it can get your web content with the ingrained links on the websites of different media outlets.

Another factor was website traffic, how many views your page gets. Using other marketing methods to drive users to your site will therefore help your SEO a lot.

Of course, the more your SEO improves, the more you’ll increase traffic to your site, helping to create a cycle of great reach!

How Using a Web Crawler Can Help Your Marketing

While web crawlers are predominantly used by search engines, not all of them are.

In fact, there are many publicly available paid or free open source web crawlers available online that you could use to assist your marketing strategy. So how does this work?

Evaluate Your Website

First of all, you could task a web crawler to evaluate a website to see how it performs against others, and how search engines see them.

If you use a spider on your own website you can therefore see if it will achieve a good ranking on a search engine, and if not, what areas are in need of improvement.

Check on Your Competitors

Of course, you could also do the same with your competitors’ sites to check on who’s outperforming who.

Knowing which factors you need to improve over your main competitors can help give you an edge.

If you want to do a quick check to see if Google’s web crawler is even reading your website you can type ‘site:(your domain website)’ into the search bar.

This will show you all of your web pages that Google has indexed, ready to show up in the next relevant query. If you don’t see the pages you want, then clearly there’s an issue that you need to take care of.

Why Isn’t My Website Being Crawled?

Perhaps the page you want to show up is new and has only been recently uploaded, meaning a web crawler has not had a chance to crawl it yet.

Maybe no other external site is linking back to your website. This is a pretty important factor for search engines, so you need to invest in backlink outreach with other websites.

If your site has poor user experience and is difficult to navigate, it might have made it too hard for the spider to crawl it properly, leading it to be improperly indexed.

Also make sure you do not use tactics that could be viewed as spam on your site, as this will cause you to be blacklisted from Google.

How to Ensure Web Crawlers Can Find Your Webpages

So what can you do to make sure the pages you want to be found actually end up on a search engine’s results page? You may find that Google or another search engine can find your website easily enough, but is not displaying all the pages on the site, even if they’re important.

Here’s what you can check for:

Is the Web Crawler Being Blocked by Your Login Forms?

First of all, does your website use login forms? If any content or information is hidden behind a login page for whatever reason, a web crawler will not be able to access it.

After all the bot itself won’t set up its own account!

Web Crawlers Cannot Use Search Bars Themselves!

Also, do not try and use an internal search bar and expect people to simply use this to find pages on your site, rather than links.

Not only is this not the most user-friendly experience, but also bots do not know how to crawl through a search bar.

All they know to do is crawl through links to new pages, so if your landing page has no links to the rest of your site, the web crawler will not explore the rest of it.

Web Crawlers Prefer Text to Images, Video, or Other Media

In recent times, search engines and their web crawlers have made headway with image search, and this is still improving.

However, it’s not yet perfect, and search engines still prefer to crawl through text.

This is why you need to make sure that any content that you want to be found is written as text for easy crawling.

Do not use images, videos, or GIFs with text inside them if you actually want the web crawler to read it and index it.

It’s still beneficial to have these on your site, but make sure the actual text is included within your HTML code, otherwise, it will not show up on a results page as the crawler won’t crawl it.

How to Make Your Site Can Be Navigated Easily

Crucially, if you want a page to be crawled, it has to be linked to other pages. If there are no links to it, not even from your own site, then it will be impossible for a web crawler to find it.

In general, if your site’s navigation has been poorly put together then it will be hard for anyone to traverse it, human users or web crawler.

To make sure your site is easily navigated by a web crawler here are some things you can do.

If you have a mobile site as well as a desktop one, make sure both show the same results as each other.

Remember, Web Crawlers Prefer HTML Code

Check what code you have written your site in. Some sites prefer to use JavaScript which isn’t ideal for Google.

Googlebot may be able to have a go crawling it but it won’t be as smooth as it could be.

To keep things simple, it is often best to stick to HTML code as Google is far better at reading this, making it simple to crawl.

Again, the easier it is for the web crawler, the more likely it will be rewarded with a higher search ranking.

Always Check for Errors

Try and check if a crawler is getting error messages when they try and crawl your site. Google lets you do this with its Google Search Console.

Go to Crawl Errors and type in the URLs for any pages that you are worried are not showing up in search results.

If there is an error on the page then Google Search Console will report it and tell you the nature of it, whether they are server errors, or not found errors.

Using a Web Crawler for Maintenance

A web crawler could also be used for simple site maintenance. It will help show you which links are working and if your HTML code is valid.

This will keep your pages running smoothly, and improve the user experience. The better the user experience, the more time they’ll spend on the page, and the more likely they’ll be to return, all of which helps improve your SEO.

Web Crawling to Improve User Experience

Google rewards pages with good user experience with improved positions in its rankings.

If a page is easy to navigate and provides the information the original search was looking for, Google’s crawlers will give it a higher preference.

Content is a valuable tool in any marketer’s belt, it helps engage your audience, bring new users in, and expands your reach when it is widely shared.

But it’s not just users who are reading it, but also the bots who are in charge of web crawl duties.

Web crawlers are also reading it, and how they do so can have an effect on your search engine rankings.

It’s worth thinking about how the content on your site has been produced, and whether or not it has been done so with web crawling in mind. The term used to describe how well a spider or bot reads content and information is scannability.

What is Scannability?

The most important factors for improving a piece of content’s scannability are how high-quality it is, and how relevant to the users it is.

Poorly created or designed content with either insufficient or inaccurate information is unlikely to be seen favorably by web crawlers and will not achieve high rankings on the results page.

This is why it pays to properly invest in your content marketing and using a dedicated team will improve your scannability and therefore your SEO.

The more these criteria are met, the better your content will be for users, and your position on a search engine’s results will be more favorable.

This is why it also helps to use a private web crawler to scan your own content.

It can report back on how positively the crawler views it, letting you know how a proper search engine’s bot will see it as well.

Overall, using publicly available web crawlers yourself, whether paid or free open source, is a useful practice, simply because it provides an insight into how these programs work.

By seeing how a spider scans a page, and what it looks for, as well as how it decides what pages to scan or not, it can help you get a better idea of how to prepare and create your web pages so they are designed to be web crawler friendly as possible.

This, ultimately, will let you know exactly what to do to get your website as high up on the search rankings as possible, making it quick and easy for potential customers and users to find you.

Web Crawling vs. Web Scraping

You may have also heard of a process called web scraping, also called content scraping and data scraping.

While similar to web crawling, there are some differences that set web scraping apart.

While web crawlers keep on following URLs from site to site in perpetuity, web scraping is actually much more focused and targeted.

They will often be tasked with scraping just one specific website or even just a specific page.

Web Scrapers Copy Data

The other difference is that while a web crawler merely collects the data for indexing purposes, the process of web scraping will actually copy the data and download it to another site.

Web scraping also does not just gather metadata and other unseen data like a web crawler, instead, web scrapers actually extract tangible content for download to be used on another site.

Web Scrapers Ignore Robots.txt Restrictions

Finally, web scrapers do not follow the requirements on a page’s robots.txt, so could end up straining the server’s bandwidth.

This is because web scraping does not seek the website owners’ permission, instead it will just download its content and data without checking its robots.txt.

Web scraping is therefore commonly seen to be used for more malicious purposes, which could include spam or data theft.

Malicious web scraping bots, therefore, need to be blocked.

If not, a server could fall victim to theft, user experience can be severely hurt, and the website could even crash completely.

It is possible to block bots from accessing a website, however, you need to be careful your robots.txt filters out the harmful web scrapers, yet still allows a legitimate crawler to browse.

This will protect the server without harming the website’s SEO.

What Are the Different Types of Web Crawlers?

So now we know what web crawlers do, how they work, and how they can help marketers, let’s take a look at the different types of crawler that search engines use on the internet today.

As mentioned earlier, the most common users of web crawlers are search engines, using them to crawl and index the many pages across the internet. Here are the ones used by the biggest:

Google – Googlebot

Googlebot is Google’s main crawler but is actually composed of two web crawlers.

These are Googlebot Mobile and Googlebot Desktop, designed for browsing the different platforms to index both kinds of sites.

With this in mind, it’s important to make sure your website is mobile-friendly for easy crawling by Googlebot Mobile, as this will help boost search rankings.

The search giant also uses a number of other web crawler browser bots for different purposes.

These include Googlebot Images, Googlebot Videos, Googlebot News and AdsBot.

All of these have a specific type of content they focus on as their names suggest.

Bing – Bingbot

Bingbot is the main web crawler for Microsoft’s Bing. It covers most of Bing’s everyday crawling needs.

However, Bing does use a few more specific crawlers, much like Google. These are:

BingPreview which is used to generate page snapshots and has both desktop and mobile variants; AdldxBot which crawls ads and follows through to the websites linked in those ads; and MSNBot which was originally Bing’s main web crawler, but has since been relegated for only minor crawl duties

Baidu – Baidu Spider

Baidu is the main search engine in China and is actually the fourth largest website according to the Alexa Internet Rankings, so it has a huge number of users.

Google is unavailable in China, so if you’re looking to expand your marketing into the country a good knowledge of how Baidu Spider works will help make sure Baidu will index your site.

One thing to remember is that it will have high latency when crawling a site hosted outside of China, hurting its SEO as crawlers do not like a slow website.

You can mitigate this by using a Content Delivery Network on your website. This will help speed up your site for Chinese users, making it easier for Baidu Spider to crawl through your pages without getting slowed down.

There are other slight differences too. For example, Baidu Spider focuses mostly on homepages, while Googlebot places more relevance on internal pages.

Baidu Spider also prefers fresh content and information, rather than long, in-depth articles.

Yandex – Yandex Bot

Yandex is Russia’s main search engine, and it uses its own web crawler, Yandex Bot.

The platform has around 60% of the market share for search engines in Russia so if you want to target Russian users it’s worth getting to know Yandex Bot and making sure it’s given permission to crawl your sites. This allows it to index your webpage without getting blocked.

Want to Leverage Web Crawling and Other Techniques to Boost Your SEO Marketing? Contact Fannit Today

Search engines are probably the most important tool on the internet and available to all.

They are the main conduit for digital information and how the majority of users consume information on the internet. Therefore, their importance for digital marketing cannot be understated. If you want users to find your products and services you simply have to make use of search engines.

In order to use search engines effectively then it is crucial you understand how their main tool, web crawlers, work.

A thorough understanding of crawlers and bots will help guide you to optimize your site and content to make them as web crawler friendly as possible and ensure that these bots will index all your pages.

At Fannit, we have plenty of experience in SEO marketing and we know how to take advantage of web crawlers and their processes. If you want help to make your website and content perfect for a crawler to read, index, and hit the top spot on Google’s search results, then contact Fannit today.

More helpful reading: http://carl.cs.indiana.edu/fil/Papers/crawling.pdf