Mobile optimisation is crucial for SEO because search engines like Google use mobile-first indexing, meaning they predominantly use the mobile version of the content for indexing and ranking. A mobile-optimised site provides a better user experience for those on mobile devices, leading to longer visit durations, lower bounce rates, and more engagements—all positive signals to search engines. Since a significant portion of internet traffic comes from mobile devices, a site that is not optimised for mobile may suffer in both user experience and search engine rankings. Additionally, features like fast loading times and easy navigation on mobile are factors that search engines consider when ranking sites.

Alt attributes in images contribute significantly to SEO by providing a text alternative for search engines to understand image content. This is particularly important as search engines cannot interpret the content of images directly. Alt attributes help in ranking within image search results and enhance the overall accessibility of the website, which is a factor in search engine rankings. They also provide context to images, which can result in better user experience and potentially longer time spent on the page, indirectly boosting SEO. Properly labelled images can drive traffic from image searches and contribute to the page's relevance and context.

A strong social media presence can indirectly impact SEO. While social signals such as likes and shares are not direct ranking factors, the content shared across social media platforms can lead to increased visibility and traffic to a website. This increased engagement can lead to more backlinks, which are a significant ranking factor. Additionally, profiles in social media are often ranked in search results, increasing the visibility of a brand or website. Social media can also affect local SEO as real-time posts and location-based interactions can increase a business's presence in local search results.

Sitemaps are important for SEO as they act as a roadmap of a website, outlining all the available pages and content to search engines. A well-structured sitemap enables search engine bots to crawl a website more intelligently and efficiently. This can significantly affect a website's search engine ranking by ensuring that all pages are found and indexed. Additionally, sitemaps can provide metadata about pages on a site, such as when a page was last updated, the frequency of changes, and the importance of pages in relation to others. This information can help search engines prioritise the crawling and indexing of content.

Search engines use robots.txt files to understand which parts of a website should not be processed or scanned by web crawlers. This file is crucial for SEO as it allows webmasters to communicate with search engines about what content should not be indexed. By specifying which URLs to ignore, it prevents the crawling of duplicate content, private areas, or sections with thin content that could potentially dilute the quality of the website's indexed pages. Effectively using robots.txt can improve a site's SEO by ensuring that only the most valuable content is considered for ranking.