Knowing how search engines work can improve your search engine presence dramatically, as you’re able to learn the intricacies of getting your site to rank well in search engine results pages.
This presence can then return more visitors, leads, and even conversions, boosting your business’s revenue.
In this guide, we’re breaking down how search engines crawl, index and rank websites, as well as all of the processes that search engines use as part of their complicated systems. Let’s dive in!
How Search Engines Work
Search engines like Google work by crawling billions of pages with something they call web crawlers.
These web crawlers are also referred to as spiders or bots, and they move around the web and follow links to find new pages.
Upon discovery, these web pages may be indexed in a search engine. If they’re not, it could be due to various reasons, such as:
- Low-quality content
- Technical issues
- Robots.txt blocks
- No-index meta tags
- And so forth
If pages are indexed by the search engine after crawling, then they have the potential to start ranking for keywords. These are based on the relevance of the site’s content and the quality of the website.
Content that is highly relevant, has authority, and provides a superb user experience is usually the content that ranks high on search engines.
Search Engine Algorithms
Search engines use algorithms to find the best search results for a query.
These algorithms are designed to find the best possible answer for a query based on data, machine learning, and sorting and processing.
Across the different search engines, such as Google, Bing, and DuckDuckGo, there are many different algorithms. There are even algorithms that work together.
Examples of Search Engine Algorithms
| Algorithm | Engine | Key Features | Strengths | Weaknesses |
| PageRank | Analyses backlinks for authority | Rewards high-quality links | Vulnerable to spam | |
| BERT | Understands context with natural language | Better at complex queries | Still developing accuracy | |
| RankBrain | Adapts to user behaviour using machine learning | Personalised results | Potential for filter bubbles | |
| Penguin | Penalises spammy link-building | Maintains result quality | It may affect legitimate sites | |
| Panda | Rewards high-quality content | Improves content quality | It may be harsh on some sites | |
| Bing Algo | Bing | Includes social signals, user engagement | Holistic ranking approach | Less transparent than Google |
| Core Updates | Released multiple times per year | Rewards high quality websites | Can be harsh on what they deem to be low quality sites |
What is Search Engine Crawling?
Crawling is the process of a computer program, often referred to as a “Spider” or a “Bot”, which visits and downloads known URLs.
For example, Google’s web crawler is known as Googlebot, and it’s responsible for finding and downloading URLs. This then goes on to index them if possible.
Web Crawlers and the Crawling Process
Web crawlers perform the crawling process. Examples include Googlebot, Bingbot, and Yandex Bot.
Search engine crawlers go through a web crawling process, finding new URLs to index and rank. The process looks like the following:
- Crawl Scheduling: URLs are scheduled for crawling based on factors like update frequency and popularity.
- URL Fetching: Crawlers visit URLs and download page content.
- Content Parsing: Extracted links from fetched pages are added to the crawl queue.
- Data Storage and Indexing: Information is stored and indexed for quick retrieval during searches.
- Revisiting: Pages are revisited to update the index.
URL Discovery and Web Page Fetching
To discover URLs to crawl, website crawlers go through a URL discovery process.
These URLs are discovered in several ways. For instance, through existing sitemaps, internal or external links, and even social media and API’s.
Webpage fetching, on the other hand, is the process of retrieving the content of a webpage. This is done through HTTP requests, server response (in HTML), and JavaScript.
Understanding Search Engine Indexing
Indexing is the process of adding data and information from crawled pages to the search results.
Remember: “Crawling is not a guarantee you’re indexed.” – Rand Fishkin.
Search engines like Google may crawl your page, but it doesn’t mean they’ll always index it. This could be due to several reasons, either content or permission-related.
The Roles of the Index
The index is a massive database where search engines store and organise information.
Think of it like a library catalogue, which allows search engines to quickly locate and retrieve relevant web pages when someone enters a search query.
The entire role of the index is to:
- Store relevant data in an organised way that facilitates efficient retrieval.
- Establish a connection between keywords and web pages that contain them.
- Determine the ranking of web pages on search results based on several signals.
- Generate search results when a user enters a search query.
- Update their index constantly to discover new and more relevant pages.
Key Signals for Indexing
With indexing, certain signals indicate to search engines that a webpage is worth indexing. This includes:
| Signal | Description |
| Canonical Tags | Tells search engines the correct page to index when dealing with similar or duplicate content. |
| Meta Robots Tags | Controls whether search engines can index a page (“index”) or not (“noindex”). |
| Robots.txt | A file telling crawlers which pages or sections to crawl and index (or not). |
| Hreflang Tags | Indicates the language and target region for a page. |
| Internal Linking | Makes site navigation easy for search engines. |
| Site Speed | Faster sites are easier for crawlers to access. |
| Mobile-Friendliness | Essential for a positive user experience on mobile devices. |
| Structured Data | Provides additional information about your content to search engines. |
| Content Freshness | Regularly updated content encourages search engines to crawl your site more often. |
| High-Quality Backlinks | Links from reputable websites show search engines your site is trustworthy. |
The Importance of Search Engine Ranking
Where your business ranks for specific keywords will determine the success of your website.
The difference between ranking number 1 for a keyword and number 10 is shocking.
Even moving from position 10 to 5 on the SERPs could more than double your CTR (maybe even your conversions)
Research from Backlinko demonstrates this perfectly. Here’s an overview of the CTR breakdown by SERP position:
| Position | Click Through Rate (CTR) |
| #1 | 27.60% |
| #2 | 15.80% |
| #3 | 11.00% |
| #4 | 8.40% |
| #5 | 6.30% |
| #6 | 4.90% |
| #7 | 3.90% |
| #8 | 3.30% |
| #9 | 2.70% |
| #10 | 2.40% |
To put that into perspective, let’s do some maths:
Over 1,000 visitors, a 5% conversion rate, and a $100 conversion amount, position 1 would bring in $1,380 (on average). Position 5, however, would only bring $315.
That’s a 338.1% difference in profit – just from going from position 5 to 1. Think about that for a moment.
Factors Influencing Search Engine Rankings
There are over 200+ search engine ranking factors that platforms like Google consider when ranking a webpage. For an in-depth guide, we recommend you read this blog from Backlinko.
However, if you want a brief overview of the top 8 factors, here’s what they are:
- Quality Content: Search engines want to show the highest quality of relevant information.
- Backlinks: These are links from another website which act as a “Vote of Confidence”.
- Technical SEO: Including website speed, crawlability, and mobile friendliness.
- Keyword Optimisation: Using relevant keywords throughout your website content.
- User Experience (UX): Ensuring users have an enjoyable experience on your website through various user engagement signals.
- Schema Markup: A type of structured data you can use to help search engines understand your website.
- Social Signals: Engagement a website receives, such as likes, shares, and other social interactions.
- Brand Signals: How your brand is viewed online from an overall perspective.
Personalisation and Localisation in Search Results
Other important factors that affect search result rankings are personalisation and location. Search engines take into consideration a user’s search history, location, and device.
It’s important to note, however, that a user’s search history doesn’t always provide personalisation in search results, as Google mentioned. Only sometimes.
On the other hand, the user’s location is particularly important, especially with searches like “Open now near me” having 400% YOY growth.
With this type of search, search engines consider the user’s location as a ranking factor. If you’re looking for a coffee shop in Melbourne, you don’t want coffee shops in London to appear in your search—simple as that.
Common Issues and Challenges in Search Engine Indexing
Sometimes, pages don’t get indexed. There are various reasons behind this, so let’s dive into them.
| Issue | Solution |
| Robots.txt Blocking | Allow crawlers access to desired pages. |
| Noindex Directives | Remove or correct “noindex” tags on pages you want indexed. |
| Crawl Errors | Fix broken links, server errors, and redirects for crawl budget optimisation. |
| Duplicate Content | Use canonical tags or consolidate duplicate content. |
| Canonicalisation Issues | Ensure canonical tags point to the correct page version. |
| Thin Content | Expand and improve content. |
| Duplicate Content (External) | Create original and unique content. |
| Low-Quality Pages | Regularly review and update pages to be error-free and up-to-date. |
| Unnatural Links | Build high-quality, natural backlinks. |
| Over-Optimization | Use keywords naturally and prioritise valuable content. |
| Server Issues | Ensure server reliability and monitor for downtime or errors. |
| New Website | Submit sitemap, build backlinks, and create high-quality content. |
| No Sitemap | Create and submit an XML sitemap. |
| Blocked Resources | Ensure essential resources (JavaScript, CSS, images) are accessible to crawlers. |
| Deep Pages | Improve internal linking to deep pages (max crawl depth should be 3 pages) |
| Flash Content | Replace Flash content with modern formats. |
Remember, “Successful SEO is not about tricking Google. It’s about PARTNERING with Google to provide the best search results for Google’s users.” – Phil Frost
Conclusion
Learning how search engine’s work and how you can use this to your advantage when optimising your website is vital. Need some help with your site’s content creation, technical SEO or link building? That’s where we come in. Speak to a member of our team to find out more about how we can help you today.
FAQs
How long does it take for a webpage to be indexed?
There isn’t a set time for how long a webpage will take to be indexed. It can be from a few hours to several weeks if it fulfils index requirements.
Can search engines index all types of content, such as images and videos?
Yes. Search engines analyse text, images, and videos that are uploaded online. These are also crawled and indexed in their databases.
How do search engines determine the relevance of search results?
Search engines use very complex algorithms to determine the relevance of a web page. These algorithms look at the search, the keyword intent, the authority of sources, engagement, geography, personal preferences, and more.
