How do email image sizes affect deliverability and Gmail promotions tab placement?

Key findings

• Direct Impact: Research suggests that image file size itself might not directly impact deliverability. However, the total email size, which includes images, can be a factor.
• Loading Time: Large images can significantly increase email loading times, especially for recipients with slower internet connections. This can lead to a poor user experience and potential disengagement.
• User Engagement: If emails take too long to load, recipients may abandon them, negatively impacting open and click-through rates. These engagement metrics indirectly influence sender reputation and future deliverability. You can learn more about how to improve low Gmail email open rates on our dedicated page.
• Promotions Tab: Gmail's Promotions tab is primarily for marketing emails. While image size isn't a direct trigger, heavily image-laden emails (especially if they resemble brochures or ads) are more likely to be classified as promotional. Understanding Gmail's tab changes is key.
• Content Ratio: Some studies suggest that if an email has sufficient text content (e.g., 500 characters or more), the content-to-image ratio has minimal impact on deliverability, indicating that overly image-heavy emails with little text might be viewed less favorably by spam filters.

Key considerations

• Optimal Size: While there's no single magic number, an overall email size (including all assets) of under 100KB is often recommended. This helps ensure quick loading.
• Image Optimization: Always compress and optimize images for web use without sacrificing quality. Use appropriate formats like JPG for photos and PNG for graphics with transparency. Our guide on email image file sizes and design tradeoffs provides more detail.
• Testing: Regularly test your emails with various email clients and devices to see how quickly they load and where they land (e.g., inbox, promotions, spam). Email testing tools can provide valuable insights.
• Balance Content: Maintain a healthy text-to-image ratio. While images are crucial for engagement, ensure your email has sufficient plain text content to convey your message, especially if images fail to load. This helps protect email deliverability for image-only emails.

Key opinions

• Initial Concern: Marketers are often worried that specific image sizes in kilobytes could negatively affect email deliverability, with some emails already landing in the Gmail Promotions tab.
• Seeking Guidance: There's a common desire to understand a 'goal range' for image sizes to optimize email performance proactively, even before making content or design changes.
• Promotional Impact: While some marketers suspect image size plays a role in Gmail Promotions tab placement, they also acknowledge other factors, such as all-caps subject lines, might be more influential.

Key considerations

• Pre-emptive Optimization: Many marketers aim to address potential deliverability issues, including those related to image sizes, as a preventative measure before overhauling email content and design. If you're encountering deliverability challenges, our guide on why your emails are going to spam can help.
• Testing Tools: Utilizing content analysis tools that perform spam filter checks is crucial for identifying potential issues, including those related to email size and content ratios. This is a key step in running an email deliverability test.
• Holistic Approach: Instead of focusing solely on image size, marketers should consider all elements that might influence deliverability and tab placement, such as subject line capitalization and overall email content. You can read more about best practices for using images in email marketing.

Key opinions

• No Hard Rule: Experts largely agree that there's no strict, universal rule for optimal image sizes. Instead, they recommend continuous testing to understand how different sizes perform.
• Promotional Nature: Emails are typically routed to the Promotions tab because their content is identified as promotional, regardless of image size. This placement is often seen as beneficial, as recipients in this tab are expecting marketing content.
• Total Message Size: While image sizes themselves may not be a direct filter, the overall message size can influence spam filtering decisions at providers like Gmail.
• Path of Least Resistance: When an email system flags image size or any other content element, it's best to adjust to avoid potential deliverability issues, choosing the simplest path to inbox success.

Key considerations

• Content Analysis Tools: Experts highly recommend using content analysis tools that include spam filter checks. These tools can identify issues related to email content, including potential flags for image sizes or overall message size.
• Seedlist Testing: Implementing seedlist testing is crucial for understanding actual inbox placement and identifying how different content elements, including image sizes, might affect delivery across various providers. This is a core part of troubleshooting Gmail deliverability.
• Reputation Management: Building and maintaining a good sender reputation is paramount. Interrupting recipients with irrelevant content, even if well-designed, can lead to spam complaints, damaging reputation. Our guide on domain reputation provides deeper insights.
• Gmail's Filtering: Gmail's algorithms are sophisticated and consider many factors beyond just image size for tab placement. Focus on the overall user experience and relevance of your content.

Key findings

• Spam Filter Criteria: Inbox providers' spam filters evaluate emails based on various content elements, including images, links, and subject lines, as part of their comprehensive assessment. They don't just look at image size alone.
• Overall Content: The classification of an email (e.g., to the Promotions tab) is more heavily influenced by its overall content and purpose rather than specific components like image file size. An email's commercial nature is key.
• Engagement Metrics: User interaction, such as open rates and click-through rates, significantly influences an email's placement. Emails that fail to load quickly due to large images can negatively affect these metrics.
• Content-to-Image Ratio: Some studies suggest that as long as an email contains a sufficient amount of text (e.g., 500 characters or more), the content-to-image ratio has minimal impact on deliverability.

Key considerations

• Email Size Limits: While specific limits vary, industry best practices often suggest keeping the total email size (including all embedded assets) below 100KB to ensure optimal loading and rendering across various email clients.
• Optimization: Prioritize optimizing all images for email use by compressing them and using appropriate resolutions. This improves user experience and can reduce the overall email size.
• Content Balance: Ensure a balanced approach to content by including both engaging visuals and substantial text. This hybrid strategy caters to diverse preferences and enhances the overall email readability and deliverability.
• Gmail's Intent: Gmail's Promotions tab is designed to help users manage their inboxes. Marketers should focus on optimizing their emails for this tab if their content is promotional, rather than trying to circumvent it, as it can lead to increased engagement if handled correctly.