What’s the best practice for image-to-text balance?

Rough rule of thumb: aim for at least 60% real text, no more than 40% image area, and never ship an all-image email. That's the balance that keeps spam filters happy, keeps your email readable when images don't load, and keeps screen readers from reading "image, image, image" to someone who can't see them.

Here's the thing most senders miss. Gmail caches images (usually fine), but first-time senders often see images blocked until the reader marks you as a known sender. Outlook blocks external images by default on most configurations. Apple Mail routes images through a proxy that can delay or break loading. If your message is trapped inside a PNG, a meaningful chunk of your audience sees a blank email with a "Hi, captain@deepcurrent.io" at the top and nothing else.

A quick 5-step pre-send check:

1. Preview with images off. Most ESPs have this toggle. Does the email still make sense? If not, add more text.
2. Write alt text that earns its place. "Summer sale banner" is fine. "Shop Now" is a missed opportunity. Write what the image communicates, not what it is.
3. Keep your primary CTA in HTML text, not baked into the image. Bulletproof button code survives image blocking. A "Shop Now" graphic doesn't.
4. Put headline and value prop in text above the hero. Even two lines makes a difference in both filter scoring and reader experience.
5. Verify your ratio in the rendered source. Strip HTML tags in your head, count the words versus count the images. Under 100 words and over 5 images is a red flag.

What alt text actually does: it's what screen readers announce, what shows when images are blocked, and what filters can read (unlike the image itself). It's not magic body copy though. Filters weight alt text lower than real body text, so don't try to stuff your whole message into alt attributes.

If you want a second set of eyes on a template, the Review My Emails SOS hotline is free. Also worth a read: alt text best practices and how major clients handle blocked images.