If a picture is worth a thousand words, what is it worth to people who cannot see? In our digital world, it is easy for people with a visual disability to miss critical information or have a frustrating and negative experience. Imagine, for example, that a keynote speaker sends out their presentation after a conference. The presentation contains infographics to illustrate a key point. Without descriptions of the infographics, anyone with a visual disability cannot understand the infographic and misses out on key information.

Alternative text (alt text) is descriptive text which conveys the meaning and context of a visual item in a digital setting, such as on an app or web page. When screen readers such as Microsoft Narrator, JAWS, and NVDA reach digital content with alt text, they will read the alt text aloud, allowing people to better understand what is on the screen. Well-written, descriptive alt text dramatically reduces ambiguity and improves user experience.

People hear words objectively but understand them subjectively. This topic describes how to understand, write, and use effective alt text in Microsoft 365 products.

A group of people sitting in front of a computer

When to use alt text?

Images and pictures

Make sure to convey the content and the purpose of an image in a concise and unambiguous manner. The alt text shouldn’t be longer than a sentence or two—most of the time a few thoughtfully selected words will do. Consider what is important about an image. For example, important context might be the setting, the emotions on people's faces, the colors, or the relative sizes.

The alt text pane showing an example of a good alt text.

Do not repeat the surrounding textual content as alt text or use phrases referring to images, such as, "a graphic of" or "an image of." In the example below, the alt text is referring to the image and does not describe the content of the image sufficiently.

The alt text pane showing an example of a bad alt text.

 You can also add alt text as an argument to the IMAGE function either by using text in quotes or by using a cell reference that contains the text. For example, IMAGE("www.contoso.com/logo.jpg", "Contoso logo"). 

Diagrams, flow charts, and charts

When dealing with objects that give detailed information, such as an infographic, use alt text to provide the information conveyed in the object. Describing a chart as ‘A bar chart showing sales over time,' for example, would not be useful to a blind person. Try to convey the insight; for example, ‘A bar chart showing sales over time. In July, sales for brand A surpassed sales for brand B and kept increasing throughout the year.’ Alt text should also clearly describe the beginning point, progress, and conclusion of flow charts.

A pie chart for pie sales showing an example of a good alt text.

Videos

Videos that don't explain their content require alt text to describe the visual experience, even if the user hears music, background sounds, and speech. Alt text should describe the content and purpose of the video.

Ideally, a video should contain a second audio track with a description of the video elements that are purely visual and not accessible to people with a visual disability.

Tables

The Microsoft 365 Accessibility Checker does not flag if a table is missing alt text. However, it is always a good practice to write a clear, descriptive, and concise alt text for a table.

When not to use alt text?

Decorative visual objects

Decorative objects add visual interest but aren’t informative (for example, stylistic borders). People using screen readers will hear these are decorative so they know they aren’t missing any important information. To mark a visual as decorative, simply select the Mark as decorative checkbox when the Alt Text pane is open. The text entry field becomes grayed out.

Image marked as decorative in the Alt text pane.

Tip: If you export your document as a PDF, any visuals you have marked as decorative will be automatically tagged as artifacts, which means they will be ignored by screen readers when navigating through PDFs. 

Slicers

If the Microsoft 365 Accessibility Checker doesn't flag an object when it's missing alt text, you don't have to write alt text for it. A slicer is an example of such an object.

How to add alt text to an object?

For instructions on how to add alt text in Outlook, Word, Excel, and PowerPoint, go to Add alternative text to a shape, picture, chart, SmartArt graphic, or other object.

Tips for using alt text in Microsoft 365

  • Remember to use the Microsoft 365 Accessibility Checker during your review process. It checks that all relevant visual content has alt text and also gives you other suggestions for improving the accessibility of your content, such as checking contrast ratios. To run the Accessibility Checker, simply click the Review tab on the ribbon, and then click Check Accessibility. For more info on the Accessibility Checker, go to Improve accessibility with the Accessibility Checker.

  • Do not use a file name, duplicate text, or URLs as alt text. The Accessibility Checker will flag these since they are not useful to someone with a visual disability. For more info, go to Rules for the Accessibility Checker.

  • If there is a group of objects that forms a semantic group, such as a group of photos that all show dogs, assign alt text for the whole group. If objects have been grouped together for formatting reasons, ungroup the objects and assign appropriate alt text for each object.

Note: If you have used Microsoft 365 for a while, you might have noticed that the Alt Text pane used to have two fields, Title and Description. Now we use a single Description field in most of our apps—it has been found that having a single field is easier and less confusing for both you as the author and also anyone using a screen reader to consume the content.

Automatic alt text

In Microsoft 365, alt text can be generated automatically. When you insert a picture, you might see a bar show up at the bottom of the picture with automatically generated alt text.

In Office 2019, alt text is not generated automatically when you insert an image. If you want to add automatic alt text, select the Generate a description for me button in the Alt Text pane. Depending on the content of the image, sometimes the feature gives you descriptive tags and sometimes you get full sentences.

If automatic alt text is generated, remember to review and edit it in the Alt Text pane and remove any comments added there such as "Description generated with high confidence."

An image with automatically generated alt text at the bottom edge of the image in Word for Windows.

Turn automatic alt text on

Note: Before you can use automatic alt text, you might have to enable Microsoft 365 Intelligent Services in any Microsoft 365 product. Select File > Options > General and check that Enable services is selected under Microsoft 365 intelligent services. For more info, refer to Connected experiences in Microsoft 365.

  1. Select File > Options > Accessibility

  2. Check that Automatically generate alt text for me is selected under Automatic Alt Text.

Approve automatic alt text

  1. In the  Microsoft 365 app, right-click the item whose alt text you want to review and then select Edit Alt Text. The Alt Text pane opens.

  2. If the alt text is satisfactory, select the Approve alt text checkbox.

Automatic alt text shown in the Alt Text pane with the Approve alt text checkbox selected.

Turn automatic alt text off

  1. Select File > Options > Accessibility and unselect Automatically generate alt text for me under Automatic Alt Text.

Where to find alt text functional guidelines

Get additional resources to help you write effective alt text:

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