Understanding crawlers in SEO: a 10-point guide

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What are crawlers in SEO?

Search Engine Optimisation (SEO) is one of the main ways of attracting traffic to a website. website.

Crawlers play an essential role in this process, and it is crucial to understand how they work and their impact on your search engine ranking, such as Google.

1. The role of crawlers in SEO

A exploration robotalso known as indexing robot or crawlerA web crawler is an automated piece of software that crawls websites and indexes their content. By studying the structure and content of a site, robots help determine its relevance and authority in relation to other sites, enabling search engines such as Google to rank pages and display them in search results according to their relative importance.

2. How do crawlers work in SEO?

Crawlers constantly move from one web page to another, following the links they encounter. When a robot finds a new page, it reads and analyses its content, taking note of certain key elements such as keywords and meta tags, and then indexes this information in the search engine database.

Exploration and indexing process

The robot visits a web page and detects the links.
The robot follows each link and discovers associated pages.
The new pages are analysed and indexed in the search engine database.
The robot continues to explore the following links to find even more pages.

3. Key elements analysed by exploration robots

Several factors are taken into account when a robot analyses a web page:

Content Text, images and other multimedia elements on a page are used to assess its importance and relevance to user requests.
Structure The way in which a site is organised and its pages are interconnected plays an essential role in determining its quality and credibility in the eyes of search engines.
Meta tags These HTML contain information about the page, such as its title, description and associated keywords. Crawlers use this information to help classify and index the page content.
Incoming links Links from other sites to your site can indicate its popularity and credibility, which can have a positive impact on your ranking in search results.

4. The different types of exploration robot

There are several types of exploration robot, the main ones being :

Googlebot Google crawler: This is the best-known and most widely used crawler. It indexes websites based on Google's algorithm.
Bingbot This robot belongs to BingMicrosoft's search engine.
Yahoo ! Slurp This is the crawler for the Yahoo! search engine.
Yandex Bot This robot crawls sites on behalf of the Russian search engine Yandex.

Specialised robots

As well as general bots, there are also bots that specialise in indexing specific content such as images, videos or news. For example :

- Googlebot-Image: deals specifically with image indexing.
- Googlebot-News: explores news sites.
- Googlebot-Video: indexes videos on web pages.

5. Exploration efficiency: control and optimisation

To make it easier for robots to crawl your site, it is important to optimise the structure and content and avoid certain obstacles such as broken linksServer errors or redirect loops can hinder the robot's progress.

The effectiveness of exploration can be improved by taking the following aspects into account:

Optimising page load times
Maintain a clear, hierarchical architecture for your site, with a internal networking well thought out
Ensure that the content is easily accessible and understandable for crawlers, in particular by using appropriate meta tags
Reduce the number of broken links and unnecessary redirects
Use a sitemap XML to guide crawlers to all the important pages on your site

6. Access management for crawlers

To control the behaviour of crawlers on your site, there is a file called robots.txt file. This file, located at the root of your website, tells the robots which pages they can crawl and which they should ignore.

For example, if you want to block all robots from accessing a certain directory, you can use this text in your robots.txt file:

User-agent : *
Disallow /repertoire-interdit/

7. The limits of crawlers in terms of SEO

Despite their impressive capabilities, crawlers have their limits when it comes to crawling and indexing:

They cannot see images or read audio and video files as a human would, which is why it is so important to use appropriate meta tags to provide them with information about these multimedia elements.
They sometimes have difficulty understanding and correctly interpreting certain advanced technologies, such as the JavaScript and Ajax.
Their ability to fully explore sites whose navigation is based solely on flash links may be limited.

8. Common exploration errors

Crawlers can encounter difficulties or errors during their journey, which can have a negative impact on your SEO. Here are some common errors:

404 error a page not found or a broken link
Server error (codes 5xx): this indicates a problem with the server hosting your website
Redirect loop (too many redirects, for example).
Content accidentally blocked in the robots.txt file
Duplicate pages, which could cause an indexing conflict

9. Analyse the performance of your site using dedicated tools

To monitor the activities of crawlers on your site, there are tools such as Google Search Console and Bing Webmaster Tools, which give you a detailed analysis of your site's crawling, indexing and other SEO-related aspects. These tools can also help you identify crawling errors or areas for improvement to optimise your ranking in search results.

10. Compliance with search engine guidelines

To ensure a good ranking and avoid your site being penalised by the search engines, it is essential to follow the guidelines issued by them in terms of SEO and crawling. For example, Google regularly publishes guidelines for webmasters to help them maintain quality content and facilitate access for crawlers.

To sum up, crawlers play a crucial role in the natural referencing of your website. It is therefore important to understand how they work, to optimise the structure of your site to make their job easier, and to carefully monitor your site's performance using the analysis tools available.