Add alternative text (“alt text”) to all images. Alt text is a short description you write for images that will be read aloud by screen readers, and is required for accessibility. Alt text can also be helpful for users on mobile devices or slow internet connections, where the text can be read if images are turned off or not loading. You can find instructions for how to do this on your own site on the OpenLab Help page, Making Your Work Accessible.
- When writing alt text, do not include the words “photo of” or “image of” because the screen reader will already signal that it is an image file. Keep the description short and informative.
- For images that represent concepts and information, such as photos and illustrations, include alt text that briefly conveys the essential information presented by the image. For more on alt text for different types of images, see CUNY’s guide to image accessibility.
Video, Audio, and Animation
Video and audio must include captions to be accessible. Captions provide text versions of the words spoken in a video. They are essential for people who cannot hear the audio, and can be helpful for all users of your site, including people not fluent in the language used in the audio, or people who are working in a quiet or loud space without headphones. It can also be helpful to include a transcript as well.
Do not autoplay video and animated gifs with flashing visual content.
- People using screen readers may have difficulty hearing the reader’s output if other audio is playing at the same time.
- Quickly blinking or flashing images can trigger seizures in people with certain types of seizure disorders.
- Animations can be disorienting to many people, especially those with certain types of cognitive disorders.
- YouTube and Vimeo are the suggested video platforms for the OpenLab, and both allow you to add captions. YouTube provides instructions for adding your own subtitles and closed captions and Vimeo also has help on captions and subtitles.
- You can find information on additional tools in CUNY’s guide to video captioning tools.
It is important that documents like PDF and Microsoft Word docs are accessible. These include documents you prepare for your class, or post on an OpenLab Site. CUNY’s guide to creating accessible PDF and Microsoft Office documents provides detailed instructions for how to do this, but a few key points are emphasized below.
- PDF files are the most difficult file format to make accessible, and properly-structured HTML tends to be the most accessible.
- Use or link to a PDF only when you cannot use HTML or Microsoft Office files.
- Ensuring searchable text and tagging a PDF with hidden labels (tags) that describe the structure of the document are the minimum requirements for PDF document accessibility, in order to be correctly read by a screen reader.
- If it is necessary to use a PDF, please follow CUNY’s guidelines for:
- The Accessible Syllabus (City Tech Library; Google Slideshow)
- W3C Web Accessibility Initiative’s Images Tutorial
Information on this page is adapted from: