What the ratio really is — and what it isn't
The text-to-image ratio is often presented as a rule filters enforce. It is more useful, and more accurate, to see it as an alert: a way to spot the campaigns that drift toward “full image” before they are sent.
It flags emails where most of the message sits inside images, leaving little readable content for mailbox providers — and for people.
No major mailbox provider publishes a required ratio, and a healthy ratio alone does not guarantee inbox placement.
Why it still matters: filters assess risk from what they can read. When the offer, the argument and the sender's intent are locked inside pixels, providers have less to evaluate — and uncertainty tends to be handled with caution.
Filters can't read your images. When they can't assess the message, they assess the risk.
Why “full image” emails fail twice
The first failure is invisible. Mailbox providers analyze text to understand what an email is. A message made of pixels and almost no words looks like what spammers send to evade content filters — and it can be treated with corresponding suspicion.
The second failure is very visible. For every recipient whose email client blocks images, and for every screen reader user, a full-image email is an empty email: no offer, no argument, no CTA. For them, the campaign simply did not happen.
How to read a text-to-image check
The ratio is an estimate, expressed as a text/image balance such as 20/80 or 30/70. Read it as a trend, not a precise measurement: what matters is whether the essential message — offer, benefit, CTA — exists as real text.
5 best practices
- Keep a solid text foundation: headline, key paragraphs and CTA must survive with images turned off.
- Never ship the offer, the benefit or the CTA only inside a visual.
- Test with images disabled: if the email stops making sense, the balance is wrong, whatever the number says.
- Maintain a clear text hierarchy (headings, paragraphs): it serves screen readers and skimmers alike.
- Treat the balance as a design constraint from the brief, not a fix once the visual is done.
Common mistakes
- Exporting the whole design as one or several flat images — the “sliced” email.
- Putting legal mentions or unsubscribe information inside images.
- Counting ALT text as a substitute for visible text: it helps accessibility, but it does not replace real HTML copy.
- Padding the ratio with hidden or tiny text: invisible text is itself a well-known spam signal.
- Using an image for the main CTA button instead of a live HTML button.
How Inbox Maestro checks it
Inbox Maestro estimates the text and image coverage of your test email as rendered, assigns its classification — from balanced to full image — and shows the areas driving the result. The goal is not to chase a number, but to catch the campaigns that give filters and readers too little to read. The result appears in the Checkup section of your report, under Composition.
Frequently asked questions
What is a good text-to-image ratio for email?
A practical benchmark is a text/image ratio of at least 30/70. Between 10/90 and 20/80, the email becomes fragile; at 0/100, it is a full-image email.
Is there an official text-to-image ratio?
No. No major mailbox provider publishes a required ratio. The 30/70 benchmark is a practical guideline used to flag emails that give filters too little readable content to assess.
Are image-only emails flagged as spam?
They carry a real risk. Filters rely on text to classify content, and all-image messages resemble a classic evasion technique. The ratio is one signal among many, but a lack of readable content consistently works against you.
Does the ratio matter if my images always load?
Images do not always load: blocking, slow networks and corporate settings are common. And screen readers never load an image — only text and ALT attributes reach those users.
How is the text-to-image ratio measured?
By estimating the visual area occupied by real HTML text versus images across the rendered email, expressed as a ratio such as 30/70. Text inside images counts as image — which is precisely the problem.