Our policy for alt text and captions: use them! Any image-based or video content that we produce should include this vital piece of accessible content.
Alternative text provides text for an image on the web if it can’t be viewed due to a slow connection, an error or a user disability. Not only does alt text make things screen reader-friendly, but it also gives semantic meaning to images so they can be read by search engines. (SEO is our friend.)
Stick to these guidelines when thinking about alt text:
- Always include it for any non-text content, even when the text is “null.”
- If the image contains information, use the text to describe the image.
- If the image is a link, use the text to explain where the link goes.
- If the image is purely decoration, use alt=”” for “null” text.
- Be concise — only use the necessary words.
- Stick to sentence case with end punctuation.
- Avoid redundancy. Don’t include phrases like “image of…,” “graphic showing…” or “link to…”
If you can’t succinctly explain the content and function of the non-text content with simple alt text, you might want to consider using a text caption.
Text captions serve one of two purposes:
- To provide additional context adjacent to or surrounding a non-text element on the page.
- To allow web video and audio to be accessible to those who do not have access to audio.
When using a caption to give additional context to an element, make sure you think about alternative text first — they shouldn’t be competing with each other.
Captions for audio and video help people with hearing impairments interact with multimedia more easily. Captions also benefit non-native language speakers, users in sound-sensitive environments, and people who have trouble focusing or remembering information. Most of all, they benefit anyone viewing video without the sound turned on — and that’s a large majority of mobile device users today.
In order for captions to be helpful, they need to be synchronized and accurate. Make sure they directly match the spoken word and are relevant to the time frame of the sound available. Including a transcript along with multimedia content never hurts either.