What do each of the categories evaluate?

Performance

The Performance score specifically measures factors like page load speed, server response time, and resource optimization.

Page load speed. If a website takes too long to load, it can result in a lower score. This can be influenced by factors such as large image or media file sizes, inefficient coding, or excessive use of third-party scripts.

Server response time. If a website’s server takes too long to respond to a request, it negatively impacts user experience and can lead to a lower Lighthouse score. This could be due to server overload, slow hosting infrastructure, or other backend issues.

Unoptimized code and inefficient resource loading can also contribute to a lower Lighthouse score. If a website’s code is bloated or contains unnecessary elements, it can slow down the rendering process. Similarly, inefficient resource loading, such as render-blocking scripts or stylesheets, can hinder the website’s performance.

Accessibility

Accessibility encompasses features that ensure users, including those with disabilities, can perceive, navigate, and interact with the site effectively. Lighthouse assesses factors such as proper alt text for images, keyboard navigation, and adherence to accessibility standards.

Alt tags, or alternative text descriptions, are vital for accessibility as they convey crucial information about website images to users with visual impairments or those relying on screen readers. Without alt tags, these users might miss essential context. Alt tags allow everyone to understand the purpose and meaning of images. They also enhance SEO by providing search engines with relevant image information, improving overall website visibility and ranking.

Keyboard navigation is crucial for accessibility, providing an inclusive web experience for those with mobility challenges. It allows users to navigate a website using only the keyboard, vital for individuals with motor disabilities who may struggle with mouse interaction.

Accessibility standards, such as the Web Content Accessibility Guidelines (WCAG), outline guidelines to make digital content more accessible. WCAG focuses on principles like perceivability, operability, understandability, and robustness, providing a framework for creating inclusive websites and applications. Another notable standard is Section 508, specifically addressing accessibility for U.S. federal agencies. Adhering to these standards ensures that digital content is accessible to individuals with diverse abilities, fostering a more inclusive online environment.

Best Practices

Lighthouse evaluates factors such as efficient use of web technologies, adherence to coding standards, and the implementation of industry-recommended practices. The scan considers the proper use of meta tags, structured data, and secure connections, contributing to improved search engine optimization. It also examines the avoidance of outdated HTML features and recommends the utilization of modern web technologies for a more seamless user experience. By measuring these best practices, Lighthouse aims to guide web developers in enhancing their websites’ overall quality, compliance with industry standards, and alignment with contemporary web development practices.

SEO

The scan also evaluates various SEO practices to enhance a website’s visibility and ranking in search engine results. It assesses critical elements such as the use of descriptive meta data, including title tags and meta descriptions, to optimize content for search engines. Lighthouse also checks for proper heading structure, clear and concise content, and the avoidance of duplicate meta tags. It emphasizes the importance of creating a mobile-friendly experience, as mobile usability is a key factor in search rankings. Additionally, Lighthouse examines whether a website utilizes a sitemap and robots.txt file which helps guide search engine crawlers to your relevant content, while also obscuring content that should not be indexed by search engines. By measuring these SEO practices, Lighthouse provides valuable insights for web developers to improve their websites’ search engine performance.