Visual and media content.
WHAT EVERY IMAGE NEEDS
A source, and alternative text.
WHAT ALTERNATIVE TEXT SHOULD SAY
What the image conveys, in its context.
WHAT IT SHOULD NOT SAY
"Image of" The filename A description irrelevant to why it is there
WHAT TO DO FOR DECORATIVE IMAGES
Mark them as decorative, so assistive technology skips them.
WHY
An announced decorative image is noise.
WHAT ELSE IMAGES NEED
Dimensions specified.
WHY
So the browser reserves space, preventing the layout shifting as images load.
WHAT THAT PREVENTS
People clicking the wrong thing as content moves.
WHAT RESPONSIVE IMAGES PROVIDE
Different files for different screen sizes and densities.
WHY THAT MATTERS
Serving a large image to a phone wastes the visitor's data and time.
WHAT FORMATS TO USE
Modern compressed formats, with fallbacks Vector formats for logos and icons
WHAT TO PROVIDE FOR VIDEO AND AUDIO
Captions, and a transcript where possible.
WHAT TO NEVER DO
Play media automatically with sound.
