What are some best practices for using HTML semantic elements to improve web accessibility?

Semantic markup enhances the accessibility of web content for users with disabilities by providing meaningful information to assistive technologies such as screen readers. For example, using <nav> for navigation bars and <header> for page headers helps screen readers understand the structure of the page. There is also an SEO benefit as search engines can more accurately index and understand web pages with semantic markup, which can improve search engine rankings. Tags like <article>, <section>, and <aside> help search engines identify the key parts of a webpage, enhancing its relevance for specific queries.

Not only do semantic HTML help screen reader users understand the website or web application they are currently on, it also enhanced developer experience. As a developer, it is much easier to go through the DOM when semantic HTML is used to understand where on the page I am rather than guessing which div is the one I am looking for.

Using HTML semantics has several benefits. HTML semantics enhance accessibility by helping assistive technologies such as screen readers interpret and convey webpage content effectively and enable efficient keyboard navigation with elements like `<nav>` and `<main>`. HTML semantics also help improve search engine indexing and content discovery. This ensures a more inclusive and accessible web experience for everyone.

When you understand the layout structure of the page and the purpose of the component you are creating you get a hence of what the right semantic element is to use. Get to know the more than 100 html tags that exist, familiarize yourself what they stand for and their build-in features and you will create a experience everyone will be happy with, the end user as well as fellow developers.

Recently aria roles where even applied to element already using semantic tags to support older browsers. This is not needed any more. Only use aria roles when it is not possible to use the implicit element. Using aria roles mostly happens when working with legacy code and a huge code base. But still try to switch to implicit elements whenever possible to enhance code quality.

Use native HTML when you can. ARIA roles give you more flexibility, but think of them as supplemental. It's always good to ask if you really need ARIA in a particular use case.

Always choose a semantic HTML element over aria, and do not use aria too much. "Better to use no aria then bad aria". Additionally, do not over complicate things. If you get overwhelmed with custom applications do some research, thoroughly testing before adding a punch of stuff that maybe no one ones in the first place. As developers who do not rely on screen readers we often assume certain things of screen reader users which most likely are not the case at all.

Another caution I would offer is overuse of semantic elements. Good heading structures are sufficient in most situations. So beyond indicating the header, navigation, main and footer, I would go very lightly with adding others. Too many is potential worse than too few.

In addition to manual testing with keyboards and screen readers, WAVE and aXe are excellent tools for evaluating and identifying common accessibility issues on your web page.

First, start with automatic testing tools like axe dev tools, that will give you a first glance on how your website is doing. For manual testing, stop using you mouse and navigate the site with only the tab key. Can you reach everything on the site? Can you interact with expected elements and do you see which element receives the focus? Additionally, you can use chrome dev tools to take a look on your layout structure like landmarks and headings to get an overall understanding if the page looks like expected.

I don't think it's possible to emphasize too much the critical checks, especially in regard to semantic structures: 1. Test with at least one screen reader. Ensure what you've incorporated actually assists understanding and navigation. 2. Validate with users who use screen readers. Confirm your assumptions, and improve future designs.

When in doubt, if you NEED to use ARIA for custom components you can, however if there is a semantic/native equivalent use that first and foremost!

Don't overthink it. Do you research and read blog posts written by accessibility specialist, who are doing research with people with disabilities for a long time, adding the results, thoughts and screen reader outputs in their posts and keeping their content updated. Some suggestions are Adrian Roselli, Léonie Watson and Manuel Matuzovic.