Introduction
Website crawling is an essential process in web development and SEO. It allows search engines to explore and index the Internet and deliver the most relevant content to users. If you are an SEO professional or a website owner, you must know how website crawling works.
What is Website Crawling?
Website crawling or web crawling is the automated process of systematically browsing and indexing the content of websites. Bots, also known as crawlers or spiders, carry out this process. These crawlers “crawl” through web pages. They scan the content, follow links, and store key information for use in search engines. Without web crawlers, search engines cannot analyze or rank websites. This makes them invisible in search results. There are different types of crawling for different purposes. These are:- Complete Site Crawls: The crawler explores the entire website, following all the internal links until it exhausts all the crawlable pages. This is important for site-wide indexing.
- Page Crawls: In this case, the bot crawls individual pages. This can be done when a specific URL is submitted or updated.
- Discovery Crawl: Where the bot finds new pages that haven’t been indexed.
- Refresh Crawl: Where the bot checks previously indexed pages for updates or changes to make sure the most recent version is indexed.
How Does Web Crawling Work?
Let’s understand the crawling process through a step-by-step breakdown. Step 1: Crawl Seed List Crawlers start with a list of known URLs called a crawl seed list. This list consists of already indexed websites, user-submitted URLs, or links the search engine thinks are essential. Step 2: Fetching Pages The crawler fetches the pages by sending a request to the website’s server. It’s similar to how a user’s browser requests a page. Step 3: Scanning HTML Content Once the page is fetched, the crawler scans the HTML code. This helps them identify key information such as text content, images, metadata, and links to other pages. Step 4: Following Links After scanning the page, the crawler follows the hyperlinks it finds. This process is recurring. Every link leads to another page that can be crawled, and those pages have links to even more pages. Step 5: Storing and Indexing After gathering data from a webpage, the crawler sends the data to the search engine’s database for indexing. During indexing, the search engine analyzes the content and tries to understand what the page is about. It categorizes the page based on its topic, keywords, and relevance. This index is later used when a user searches for terms. Step 6: Re-crawling Pages Web pages are constantly updated, added, or removed. To keep search results accurate, crawlers periodically revisit and re-crawl pages to refresh the index. The frequency of this re-crawling process depends on factors such as:- How frequently the content is updated
- The page’s importance or relevance to search engines
Key Components of Crawling
There are some major elements that affect how crawling works. These elements are:1. Crawl Budget
It’s the number of pages a search engine’s crawler is allowed to crawl on a website within a specific timeframe. This budget is limited and is influenced by a website’s authority, size, and how frequently it’s updated. Websites that are larger or deemed more important receive a larger crawl budget. However, smaller or less important sites receive fewer visits from crawlers. For SEO purposes, managing the crawl budget is very important. If a search engine cannot crawl your site successfully, some pages cannot be indexed and will be invisible in search results. Delicate content, server errors, and unnecessary redirects waste the crawl budget.2. Robots.txt
This is a simple text file placed in a website's root directory. It provides directives to crawlers about which pages or sections of a website should or should not be crawled. Website owners can configure the robots.txt file to control which parts of their site are accessible to crawlers. For example, you can block certain areas of your site that contain sensitive information or duplicate content to conserve the crawl budget. But it’s important to note that not all crawlers will obey robots.text instructions, particularly malicious bots.3. Sitemaps
An XML sitemap is a map of your website’s structure provided to search engines to make crawling more efficient. It includes a list of your website's important pages and metadata about each page, such as when it was last updated and how often it changes. Sitemaps are helpful in the following scenarios:- Your website has many pages, and some may be buried deep in the site hierarchy.
- You have content that isn’t easily accessible via internal links.
- Your site has recently been updated or redesigned, and you want to alert search engines quickly.
4. Crawl Frequency and Depth
Not all pages are crawled with the same frequency. For example, news websites can have pages crawled several times a day because the content is time-sensitive. On the other hand, a static page with little to no updates can only be crawled occasionally. The depth of the crawl refers to how many layers the crawler goes through on a site. Pages closer to the homepage (higher in the site’s structure) are generally crawled more frequently than deeper pages. It’s because they are more important.How to Control Web Crawlers on Your Website
Crawling is beneficial for visibility. But there could be situations where you don’t want certain pages indexed, like confidential resources or low-priority pages. You can control how crawlers interact with your website using tools like: - Robots.txt File: It tells crawlers which parts of the site to crawl and which parts to ignore.
- Robots Meta Tag: These are tags added to the HTML of a webpage. They inform crawlers whether a page should be indexed or not. For example, the “nofollow” tag prevents a crawler from following the links on that page.
- Link Attributes: Links on your site can contain attributes like “nofollow.” They instruct bots not to crawl certain links. It can be useful for internal site management or when controlling how much of your site gets indexed.
Why is Website Crawling Important?
Website crawling is the basic element of SEO. Without crawling, search engines wouldn’t be able to index your content. So when visitors use search engines to place a query, your page will not appear in the search results. Let’s understand why it matters. - Improved Visibility
- Content Discovery
- SEO Rankings
- Keeping Information Updated
Challenges in Website Crawling You Might Face
The concept of crawling is simple. But it comes with its own set of challenges and complexities. Here are some common issues that website owners face:Duplicate Content
Duplicate content is one of the most common crawling problems. When a crawler finds identical or highly similar content across multiple URLs, it can struggle to understand which version to index. Duplicate content wastes crawl budget and can result in SEO penalties.Crawl Errors
Crawl errors occur when a crawler encounters issues trying to access your web pages. These could be due to server errors, broken links, or pages that are blocked unintentionally by robots.txt or other directives. Crawl errors can prevent pages from being indexed, so they need to be addressed as soon as they appear.Dynamic Content and Javascript
Some crawlers struggle to index dynamic content, such as pages that are heavily reliant on JavaScript. If your website uses JavaScript to load content, it’s important to make sure that it’s crawlable. For example, Google can execute JavaScript, but other search engines may not be as advanced.Orphan Pages
An orphan page is a page that isn’t linked from anywhere on your site. This makes it difficult for crawlers to find. Even if you have great content on orphan pages, crawlers won’t be able to discover them unless they are properly linked within your website.Infinite Loops
A crawler can encounter an infinite loop, such as a page that links to itself or a set of pages that keep redirecting to each other. In such cases, it can waste your crawl budget and slow down the indexing of your website.