Why you need image alt text and image descriptions

Image alt text vs image descriptions – what’s the difference?

Image alt text stands for 'alternative image text'. On websites, alt text is what appears when you hover over an image. It's also how Google understands what the image is about (and dictates whether your image shows up in Google image search or not).

On both websites and social media, this is the text that's read out by screen readers (and it's also thought that it plays into the mysterious social media algorithms).

BUT – not everyone who has trouble seeing images uses a screen reader, because they're not always user friendly (we know, we know). And just because someone is able to read your captions, doesn't mean they can process images.

This is where image descriptions come into play. Image descriptions live in the body of your social post or in the comments, meaning they can be read by everyone, not just screen readers.

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Three reasons why you should care

1. Image alt text and image descriptions are important for accessibility. They help people who have different accessibility needs – such as vision impairment – understand the purpose of an image without ever seeing it.

2. Image alt text also comes in handy when links break or web pages fail to load. If the image won’t load properly on your screen, alt text will appear in its place and explain the content of the image.

3. Adding alt text and image descriptions improves SEO. Google uses alt text to understand the content of your images and the webpage it’s embedded in. By including alt text in your content, you increase the probability of your image appearing higher in Google image search.

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How to write image alt text and image descriptions

The image alt text should be a concise description of your image, while the image description can be a bit longer, and have more personality.

Give your image description as much attention as your writing. People who can’t see the image should come away with the same information as if they had.

If you're describing a picture that's mostly text, you don't need to repeat any text that's already in the caption, because that will be pretty tedious for the user. And if you run out of space in your caption (or want to keep your captions neat), you can add your image description as the first comment – just make sure you state this within your caption.

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Here’s an example:

In this instance the Image alt text might read: A woman skipping through a green field.

Whereas an image description could read: A woman with brown hair wearing all white and holding a straw hat in her hand during the day. She skips away from the camera through a grassy field towards a lush green forest.

If you get stuck writing image descriptions, here are some people and brands doing it beautifully:

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How to add alt text on Instagram, Facebook, LinkedIn and Twitter

‍Instagram

1. Upload your image

2.Tap on advanced settings

3. Write your alt text. This should be a concise description of your image.

4. Go back to your post, and write your caption. At the end of the caption, include an image description. This should be a detailed description of your image. See below for how we style our image descriptions (but it’s totally up to you how you want to do it, as long as you clearly state that it’s the image description).

5. If you run out of space in the caption (or you’re delivering a pithy one liner and want to keep your caption clean), you can include the image description in the comments, as long as you clearly state this in the comments.

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Twitter‍

1. Upload your image

2. Tap on the button that says ALT

3. Write your alt text. This should be a concise description of your image.

4. Go back to your post, and write your caption. If you can't fit your image description in the body of your caption, tap on the blue ‘plus’ button, and add your image description as an additional tweet.

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Facebook

Facebook auto generates alt text, so you're only able to add custom alt text after you've posted your content.

1. Create a post as usual, and add an image description at the end of your caption.

2. Publish your post; then open it again.

3. Long press on the image until a menu appears. Tap on alt text.

4. On the next screen, you'll see the alt text that FB has auto generated (usually terrible).

5. Write your own alt text

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1. Upload your image

2. Tap on the button that says 'add alt text'.

3. Write your alt text. This should be a concise description of your image.

4. Go back to your post, and write your caption. At the end of the caption, include an image description. This should be a detailed description of your image.

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Need help creating accessible content or want to organise training for your team? We’re here to help.

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Who we are

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Slice & Dice