How to use ALT text for accessibility and fallback?

Effective alt text serves two audiences: screen reader users (who need the image's meaning conveyed verbally) and sighted users with images blocked (who need visual context in text form).

Best practices: Describe function, not just appearance ("Buy now button" not "blue rectangle"). Be concise but complete-aim for under 125 characters. Include key information from the image (product names, prices, offers). Style alt text with inline CSS-some clients display styled alt. Use empty alt (alt="") for purely decorative images. Never omit alt entirely-that's worse than empty.

Write alt text as if the reader can't see any images. Would they understand your email? Know what to click? Grasp the offer? If alt text alone tells the story, you've done it right. This isn't just accommodation-it's good design for the significant portion of recipients who see images-blocked by default.