How does the image to text ratio in email affect deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 21 Jun 2025
Updated 15 Aug 2025
7 min read
The question of how the image-to-text ratio in emails affects deliverability is a topic I encounter frequently. Many email marketers and senders worry that having too many images, or too few, could land their messages in the spam folder rather than the inbox. It's a valid concern, given the complexity of modern spam filters.
Historically, a disproportionate image-to-text ratio was indeed a significant red flag for spam filters. Spammers would often send emails composed entirely of images to bypass text-based content filters, embedding malicious links or deceptive messages. This practice led many ISPs (Internet Service Providers) to develop heuristics that would penalize emails with a very high image count or those that were purely image-based.
However, the landscape of email deliverability has evolved considerably. While the image-to-text ratio still plays a role, it's often less about a strict percentage and more about the overall context, sender reputation, and user engagement. It's important to understand the nuances of this factor to ensure your emails consistently reach their intended recipients.
The changing role of image to text ratio
Modern spam filtering is far more sophisticated than simply counting images versus text. Today, the primary determinant of whether an email lands in the inbox or the spam folder is sender reputation. This reputation is built over time based on factors like consistent sending volume, low bounce rates, minimal spam complaints, and adherence to email authentication standards such as DMARC, SPF, and DKIM.
While some older or less advanced spam filters, such as SpamAssassin, still incorporate image-to-text ratio into their scoring algorithms, its weight in the overall decision-making process is generally low. For most major mailbox providers, an email with a high image ratio won't be automatically blocklisted (or blacklisted) if the sender has a strong, positive reputation and the content is engaging to recipients. To understand more about how these filters work, you can read our guide on how email blacklists actually work.
However, this doesn't mean you should abandon text altogether. Image-only emails, or emails with minimal text content, still pose risks. These types of emails can lead to poor user experience if images fail to load, and they might still trigger older spam filters, particularly if other elements of your sending infrastructure or content are already borderline. We have a detailed article on why image-only emails can be detrimental to deliverability.
The risks of image-only emails
While the direct impact of image-to-text ratio on deliverability has lessened, sending emails that consist almost entirely of images still carries significant risks. These include diminished accessibility, potential blocking by email clients, and higher file sizes, all of which can negatively affect subscriber engagement and, consequently, your sender reputation. For more on this, you can review the truth behind image-to-text ratio in email campaigns.
Impact on accessibility and user experience
One of the most critical aspects often overlooked when focusing solely on ratios is accessibility. Not all recipients will view your email with images enabled, and many use screen readers or other assistive technologies. If your email's core message, calls to action, or critical information are embedded solely within images, a significant portion of your audience might miss out completely. This leads to a poor user experience, which indirectly harms your deliverability by increasing the likelihood of recipients deleting your emails or marking them as spam.
To mitigate this, always use descriptive alt text for all images. Alt text provides a textual description of an image, which appears if the image doesn't load or if a screen reader is being used. This ensures that even without seeing the image, recipients can understand its purpose and content. We recommend ensuring that image-based emails include alt text for improved deliverability.
Furthermore, providing a plain text version of your email is a deliverability best practice. This version is stripped of all HTML formatting and images, providing a fallback for recipients whose email clients don't render HTML, or who prefer a simpler view. It also serves as a crucial signal to spam filters that your email is legitimate. Check out our article on how plain text versions improve deliverability.
Poor image practices
Image-only content: Relying entirely on images for your email's message, neglecting live text.
Missing alt text: Images without descriptive alternative text, making content inaccessible.
Large file sizes: Using unoptimized, heavy images that slow down email loading.
Best image practices
Balanced approach: Combining images with ample live text to ensure clarity and accessibility.
Descriptive alt text: Adding meaningful alt text to all images for screen readers and image-blocked views.
Optimized images: Compressing images for web use to reduce email file size.
Technical considerations beyond ratio
Beyond the aesthetic and accessibility factors, the total file size of your email significantly impacts deliverability. Large emails take longer to load, consume more bandwidth, and can be frustrating for recipients, especially those on mobile data or slow connections. Mailbox providers, including Gmail, often impose limits on email size, and emails exceeding these limits may be truncated, rejected, or sent directly to spam. We explore this further in our article on how email image sizes affect deliverability.
Images are typically the largest contributors to email file size. While the image-to-text ratio might not be a direct spam filter trigger, a high ratio often correlates with a larger overall email size. This is especially true if images are not properly optimized for web use. Uncompressed images, or those with unnecessarily high resolutions, can inflate your email's size dramatically. You can learn more about managing file sizes from Mailjet's advice on email file sizes.
To ensure optimal deliverability, it's crucial to compress your images before embedding them in your emails. Tools are available that can reduce image file sizes significantly without compromising visual quality. Additionally, consider the practical application of images; are they enhancing the message or merely decorative? Every image should serve a purpose.
Element
Recommendation
Image-to-text ratio
Aim for a balanced approach, typically around 60-80% text to 20-40% images. Avoid image-only emails.
Image alt text
Always include descriptive alt text for every image.
Total email size
Keep total email size under 100KB to 200KB for optimal loading and deliverability.
Plain text version
Always include a plain text version as a fallback.
Views from the trenches
Best practices
Always include a meaningful plain text version of your email to ensure accessibility and deliverability.
Use descriptive alt text for all images so content remains understandable if images do not load.
Optimize images to reduce file size, which improves loading speed and overall email performance.
Common pitfalls
Sending emails that are entirely image-based, which can trigger spam filters and hinder accessibility.
Neglecting to include alt text for images, making your email unreadable for some recipients and screen readers.
Using uncompressed images that significantly increase email file size and slow down loading times.
Expert tips
Monitor your engagement metrics closely; high deletions or spam complaints are bigger red flags than image ratio.
Test your emails across various clients and devices to see how images render and ensure consistent display.
Prioritize user experience by making sure your core message is always clear, whether images load or not.
Marketer view
Marketer from Email Geeks says predominantly image-based emails are bad practice due to accessibility issues, as some recipients cannot access mail with sight issues.
2020-10-14 - Email Geeks
Marketer view
Marketer from Email Geeks says this issue will likely become more prominent as smart speakers start reading out emails.
2020-10-14 - Email Geeks
Striking the right balance
In modern email marketing, a rigid adherence to a specific image-to-text ratio is less impactful than it once was. The focus has shifted from simple content checks to a more holistic evaluation of sender reputation, engagement, and user experience. While it's true that an extremely high image ratio could still be a minor flag for some legacy spam filters, it's rarely the sole reason for deliverability issues.
Instead, successful email deliverability hinges on building and maintaining a positive sender reputation. This means consistently sending valuable content, getting high engagement rates (opens, clicks), and minimizing negative signals like spam complaints or unsubscribes. Ensuring your emails are relevant and desired by your recipients will have a far greater impact than any specific content ratio.
My advice is to prioritize accessibility and user experience. Always include meaningful live text alongside your images and provide robust alt text. Optimize image file sizes to keep your overall email lightweight, ensuring faster loading times and a smoother experience for all subscribers. These practices not only improve the recipient's journey but also contribute positively to your sender reputation, which is the true cornerstone of strong deliverability. For more information, read our guide on why emails go to spam.
Ultimately, a balanced approach to email design, where images enhance rather than replace text, is the most effective strategy. Focus on creating engaging, accessible, and technically sound emails, and you'll be well on your way to consistent inbox placement. You can also explore technical solutions for boosting deliverability rates.
Gmail, often impose limits on email size, and emails exceeding these limits may be truncated, rejected, or sent directly to spam. We explore this further in our article on how email image sizes affect deliverability.
