Alt text for email marketing images

Open your last campaign in Outlook on a locked-down corporate machine and there's a decent chance you'll see it the way many of your subscribers do: gray boxes where the hero image should be. On social, a missing image is rare. In email, it's routine — which makes email the one channel where alt text isn't just an accessibility layer. It's your backup copy.

Email is the one channel where images actually vanish

Some email clients — Outlook on the desktop is the classic example — block image downloads by default until the reader clicks to load them. Add corporate security policies, privacy tools that strip remote content, and slow connections, and a meaningful share of your list reads your email before (or without ever) seeing a single image in it.

When that happens, the alt text is what renders in the empty frame. If you wrote it, the reader still gets "Fall collection: three wool coats, up to 40% off." If you didn't, they get a gray rectangle and a filename. Same send, very different email.

One field, three readers

That single attribute serves three audiences at once. Screen reader users hear it read aloud — same as everywhere else on the web. Image-blocked readers see it in place of the image. And every reader sees it for a moment on a slow connection, while the images are still loading. Write it once, and it works all three shifts.

Support isn't uniform — a few older desktop clients bury alt text behind a security notice or skip it entirely — but that's an argument for writing it, not against: the clients that do show it are exactly where images are most likely to be blocked.

What to write — and when to write nothing

The rules you already know still apply: lead with the subject, keep it under roughly 125 characters, skip "image of." Email adds two twists. First, if the image carries your offer — a discount, a date, a headline baked into the graphic — the alt text must carry it too, or blocked-image readers never see the point of the email.

Second, email templates are full of purely decorative images — spacers, dividers, border graphics. Give those an empty alt attribute (alt="") so screen readers skip them instead of announcing junk. And avoid quotation marks inside the text itself; they can break the HTML attribute and cut your description off mid-sentence.

Where the field hides in your email tool

Every major email builder has an alt text field; none of them make it prominent. In most, you select the image block and look for "alt text" or "alternative text" in the block's settings panel — often below the fold, after the link and alignment options. It's worth finding once, because after that the only remaining cost is writing the words.

That's the part worth automating. A campaign with eight images means eight descriptions at the exact moment you're trying to hit send — which is why the field so often ships empty.