If you build web pages or publish content online, you may be familiar with alt text.

Alt texts are short captions you can add to images, describing what's in the image. These are helpful to visually impaired users, who rely on screen readers to use the internet.

When a screen reader encounters a picture with alt text, the alt text will be read aloud, allowing those users to understand what you've posted.

Twitter makes it easy to write alt text for images when you use the Twitter website on your Mac or PC, as well as the Twitter mobile app for iPhone and Android devices.

1. Using the Twitter app on your iPhone or Android, create a Tweet in the usual way. Tap the Image button to add an image to your Tweet and select a photo.

2. In the lower right corner of the image, tap "+ALT." This is the button that lets you add alt text to the tweet.

Use the +ALT button in the image to add alt text. Dave Johnson/Business Insider

3. The first time you use alt text, the "Add descriptions" pop-up window appears, which explains the purpose of alt text. Tap "Sure" to dismiss it.

4. Type your description. You have up to 1000 characters, though you probably shouldn't use all that space good alt text is usually under about 100 characters, no longer than an actual tweet.

5. When you're finished, tap "Done." You won't be able to see the alt text you just created, but you can verify it's there by tapping the "Alt" button again.

6. When you're ready, publish the tweet.

Type your alt text and tap "Done" to complete your tweet. Dave Johnson/Business Insider

1. Open Twitter in a browser on your Mac or PC and create a tweet in the usual way. Click the Image button to add your photo to the tweet.

2. Below the image and to the right of "Tag people," click "Add description."

Alt text is added to a tweet in a browser using the "Add description" link. Dave Johnson/Business Insider

3. The first time you use alt text, the "Add descriptions" pop-up window appears, which explains the purpose of alt text. Tap "Sure" to agree to dismiss it.

4. Type your alt text in the "Description field." You can use up to 1000 characters, though you probably shouldn't use all that space good alt text is usually under about 100 characters, no longer than an actual tweet.

5. When you're finished, click "Save." To return to your alt text, you can now click "ALT" in the lower left corner of the image.

6. When you're ready, publish the tweet.

Add your alt text in the Description field and click "Save" when you're done. Dave Johnson/Business Insider

Insider Inc. receives a commission when you buy through our links.

Go here to read the rest:

How to add alt text to images on Twitter so that they can be read with screen readers - Business Insider - Business Insider