Accessibility Reference

By Kayce Basques

Technical Writer, Chrome DevTools & Lighthouse

This page is a comprehensive reference of accessibility features in Chrome DevTools. It is intended for web developers who:

• Have a basic understanding of DevTools, such as how to open it.
• Are familiar with accessibility principles and best practices.

The purpose of this reference is to help you discover all of the tools available in DevTools that can help you examine a page's accessibility.

Overview of accessibility features in Chrome DevTools

This section explains how DevTools fits into your overall accessibility toolkit.

When determining whether a page is accessible, you need to have 2 general questions in mind:

1. Can I navigate the page with a keyboard or screen reader?
2. Are the page's elements properly marked up for screen readers?

In general, DevTools can help you fix errors related to question #2, because these errors are easy to detect in an automated fashion. Question #1 is just as important, but unfortunately DevTools can't help you there. The only way to find errors related to question #1 is to try using a page with a keyboard or screen reader yourself. See How To Do An Accessibility Review to learn more.

Audit a page's accessibility

In general, use the Audits panel to determine if:

• A page is properly marked up for screen readers.
• The text elements on a page have sufficient contrast ratios. See also View the contrast ratio of a text element in the Color Picker.

To audit a page:

1. Go to the URL that you want to audit.

2. In DevTools, click the Audits tab. DevTools shows you various configuration options.

   

   Figure 1. Configuring audits

   Note: The screenshots in this section were taken with version 69 of Chrome. You can check what version you're running at chrome://version. The Audits panel UI looks different in earlier versions of Chrome, but the general workflow is the same.

3. For Device, select Mobile if you want to simulate a mobile device. This option changes differently your user agent string and resizes the viewport. If the mobile version of the page displays differently than the desktop version, this option could have a significant effect on the results of your audit.

4. In the Audits section, make sure that Accessibility is enabled. Disable the other categories if you want to exclude them from your report. Leave them enabled if you want to discover other ways to improve the quality of your page.
5. The Throttling section lets you throttle the network and CPU, which is useful when analyzing load performance. This option should be irrelevant to your accessibility score, so you can use whatever you prefer.
6. The Clear Storage checkbox lets you clear all storage before loading the page, or preserve storage between page loads. This option is also probably irrelevant to your accessibility score, so you can use whatever you prefer.

7. Click Run Audits. After 10 to 30 seconds, DevTools provides a report. Your report gives you various tips on how to improve the page's accessibility.

   

   Figure 2. A report

8. Click an audit to learn more about it.

   

   Figure 3. More information about an audit

9. Click Learn More to view that audit's documentation.

   

   Figure 4. Viewing an audit's documentation

See also: aXe extension

You may prefer to use the aXe extension rather than the Audits panel. They generally provide the same information, since aXe is the underlying engine that powers the Audits panel. The aXe extension has a different UI and describes audits slightly differently. One advantage that the aXe extension has over the Audits panel is that it lets you inspect and highlight failing nodes.

Figure 5. The aXe extension

The Accessibility pane

The Accessibility pane is where you can view the accessibility tree, ARIA attributes, and computed accessibility properties of DOM nodes.

To open the Accessibility pane:

1. Click the Elements tab.
2. In the DOM Tree, select the element which you want to inspect.
3. Click the Accessibility tab. This tab may be hidden behind the More Tabs button.

Figure 6. Inspecting the h1 element of the DevTools homepage in the Accessibility pane

View an element's position in the accessibility tree

The accessibility tree is a subset of the DOM tree. It only contains elements from the DOM tree that are relevant and useful for displaying the page's contents in a screen reader.

Inspect an element's position in the accessibility tree from the Accessibility pane.

Figure 7. The Accessibility Tree section

View an element's ARIA attributes

ARIA attributes ensure that screen readers have all of the information that they need in order to properly represent a page's contents.

View an element's ARIA attributes in the Accessibility pane.

Figure 8. The ARIA Attributes section

View an element's computed accessibility properties

Note: If you're looking for computed CSS properties, see the Computed tab.

Some accessibility properties are dynamically calculated by the browser. These properties can be viewed in the Computed Properties section of the Accessibility pane.

View an element's computed accessibility properties in the Accessibility pane.

Figure 9. The Computed (Accessibility) Properties section

View the contrast ratio of a text element in the Color Picker

Some people with low vision don't see areas as very bright or very dark. Everything tends to appear at about the same brightness, which makes it hard to distinguish outlines and edges. Contrast ratio measures the difference in brightness between the foreground and background of text. If your text has a low contrast ratio, then these low vision users may literally experience your site as a blank screen.

The Color Picker can help you make sure that your text meets recommended contrast ratio levels:

1. Click the Elements tab.

2. In the DOM Tree, select the text element that you want to inspect.

   

   Figure 10. Inspecting a paragraph in the DOM Tree

3. In the Styles pane, click the color square next to the element's color value.

   

   Figure 11. The color property of the element

4. Check the Contrast Ratio section of the Color Picker. One checkmark means that the element meets the minimum recommendation. Two checkmarks means that it meets the enhanced recommendation.

   

   Figure 12. The Contrast Ratio section of the Color Picker shows 2 checkmarks and a value of 16.10

5. Click the Contrast Ratio section to see more information. A line appears in the visual picker at the top of the Color Picker. If the current color meets recommendations, then anything on the same side of the line also meets recommendations. If the current color does not meet recommendations, then anything on the same side also does not meet recommendations.

   

   Figure 13. The Contrast Ratio Line in the visual picker

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