How does the browser determine which CSS rule to apply when there are conflicts?

The browser determines which CSS rule to apply when there are conflicts by comparing the specificity of each rule. Specificity is a scoring system that evaluates how specific a selector is in terms of its application to elements on the page. The more specific a rule is, the higher its priority when multiple rules could apply to the same element.

For instance, an ID selector is more specific than a class selector, and thus, if both are applied to the same element, the styles from the ID will take precedence over those from the class. Similarly, inline styles are given the highest specificity and will override styles in external stylesheets. By using this specificity hierarchy, browsers provide a structured framework to resolve conflicts in CSS rules, which is crucial for maintaining consistent styling across web pages.

This approach allows developers to create layered styles with varying degrees of authority, ensuring that intentional design choices are reliably rendered by the browser. The other methods mentioned, like random selection or simply applying the most recent definition, do not create a systematic way of resolving conflicts and could lead to unpredictable results. Therefore, specificity serves as a logical solution to handling CSS conflicts effectively.