Everything you need to know to write effective alt text

Open the Microsoft 365 Accessibility Checker:

1. On the Review tab, select Check Accessibility.

2. In the right Accessibility pane, issues with accessibility appear under Inspection Results.

3. Select any flagged issues to see recommended actions.

Manually view and edit alt text, or approve automatic alt text: 

1. Right-click an image, chart, or other object, and select View Alt Text. 
   Tip: On the Review tab, you can select the Check Accessibility drop down and choose Alt Text.

2. In the Alt text pane on the right, edit or approve the displayed alt text (if automatically generated).

3. If the image doesn't need alt text, such as a border, select Mark as decorative.

Turn automatically generated alt text on or off: 

1. On the File tab, select Options and choose the Accessibility tab.

2. Select or clear the Automatically generate alt text for me checkbox under Automatic Alt Text.

Automatic alt text generation needs Microsoft 365 intelligent services. To turn this on: 

1. On the File tab, select Options and choose General.

2. Select Enable services under Microsoft 365 intelligent services.

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.

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.

 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.

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.

Decorative visual objects

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

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.

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."

Approve automatic alt text

1. In the  Microsoft 365 app, right-click the item to review and select View Alt Text. The Alt Text pane opens.

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