Is There a Right Image-to-Text Ratio for Email? What Filters Actually Check
There is no official image-to-text ratio for email. Gmail, Outlook and Yahoo don't publish one; the 60/40 and 80/20 rules are advice from email platforms and blogs. What filters do publish is narrower: SpamAssassin's HTML_IMAGE_ONLY rules fire when an HTML email has images and only a few hundred to about 3,200 bytes of words, and its HTML_IMAGE_RATIO rules fire on a low ratio of text to image area. So the risk is the email that is mostly picture and barely any text, not a 55/45 split.
The free email image to text ratio checker counts the images and the visible text in pasted HTML and tells you which SpamAssassin band, if any, the email falls in. Here's what's behind it.
What SpamAssassin actually tests
SpamAssassin's rule file 20_html_tests.cf (read 2 November 2026) has two families of image rules:
| Rule family | What it tests | Description in the rule file |
|---|---|---|
| HTML_IMAGE_ONLY_04 to HTML_IMAGE_ONLY_32 | HTML email with images and very little text, in 400-byte bands from 0-400 up to 2,800-3,200 bytes of words | "HTML: images with 0-400 bytes of words" (and so on per band) |
| HTML_IMAGE_RATIO_02 to HTML_IMAGE_RATIO_08 | The ratio of text to image area is very low | "HTML has a low ratio of text to image area" |
Scores are set in separate files and change over time, and one rule rarely decides anything on its own; our post on how to avoid spam filters covers the signals that weigh more. Gmail and Microsoft run their own filters and don't publish their rules, but Google has described its filters as catching image-based messages, which is the same idea: an image is opaque to a text filter.
About 3,200 bytes is roughly 500 words of English. Most newsletters with real paragraphs are well past it; a promo email that is one banner, a button and "View in browser" is well under.
Where 60/40 and 80/20 come from
They're rules of thumb. Mailchimp's help on common HTML mistakes says "we recommend a ratio of 80% text to 20% images in an email" and adds that "all spam filters use different criteria for what is a healthy balance of graphics and text." Other platforms and blogs say 60/40. Neither is a mailbox provider rule. They're a reminder not to send image-only email.
Why image-heavy email has problems beyond filters
- Blocked images. Many clients don't load images until the reader allows it. An image-only email arrives as an empty frame with a few lines of alt text, if any.
- Accessibility. Screen readers read alt text, not pixels. A banner with the offer written in it says nothing without alt text.
- Weight. Images embedded as base64
data:URIs make the HTML heavier and Gmail doesn't display them. The email size checker shows how close you are to Gmail's clipping point.
How to fix an image-heavy email
- Copy the HTML from your platform's code view, or View source on a test send, and paste it into the ratio checker.
- If it reads as mostly images, move the key message (the offer, the date, the call to action) out of the image and into live text.
- Add alt text that says what each meaningful image says. Decorative spacers can have empty alt.
- Replace base64 images with hosted ones on https.
- Check the plain-text part too: the HTML to plain text tool shows what readers without HTML get.
Layout won't save a bad list
Bounces and complaints count for far more with filters than layout does. A perfectly balanced email sent to a list full of closed mailboxes still damages your reputation.
- Upload the list on the verify page. Every address gets a live mailbox check, and valid, risky and invalid download as separate files.
- Send to the valid file.
- Treat risky as unconfirmed: catch-all business domains and Microsoft's consumer domains (outlook.com, hotmail.com, live.com) often can't be confirmed either way.
Where SimpleVerifier fits
The ratio checker is free and runs in your browser; no image is loaded and nothing is uploaded. For the mailbox check, the first 100 checks are free with a Google sign-in on the verify page. Starter is $9 a month for 2,500 checks, and Pro is $39 a month with the first 100,000 checks a month at full speed, then slower, never cut off. See pricing.
Common questions
What is a good image-to-text ratio for email?
There is no official number. Mailchimp recommends about 80% text to 20% images; others say 60/40. What filters like SpamAssassin actually test is whether an HTML email with images has very little text, under about 3,200 bytes of words. Real paragraphs around a few images are normal.
Will an image-only email go to spam?
It's more likely to. SpamAssassin has rules for HTML email with images and almost no text, and Google has described its filters as catching image-based spam. It also shows as an empty box in inboxes that block images by default.
Does text inside an image count as text?
No. Text baked into an image isn't readable to a filter or a screen reader. Put the key message in live text and use alt text on every meaningful image.
Do tracking pixels count as images?
They are images in the HTML, but they're 1x1 and invisible. Our checker lists them separately and leaves them out of the image count.
Check your list before you send
Real mailbox checks over SMTP, and nothing is sent to the address. Sign in with Google and your first 100 email checks are free, no card. Plans for bigger lists are on the pricing page.