Does Google pre-fetch images differently in Gmail promotions tab vs inbox?
Michael Ko
Co-founder & CEO, Suped
Published 6 Jul 2025
Updated 16 Aug 2025
8 min read
For email marketers and deliverability professionals, understanding how mailbox providers handle emails is crucial. One area that often sparks debate and confusion is how Gmail pre-fetches images, especially concerning the Promotions tab versus the Primary inbox. It is a topic that can directly impact how we interpret our engagement metrics, particularly open rates.
A common theory, recently validated by observed data, suggests that Google's image pre-fetching behavior differs based on where an email lands. Specifically, it appears that images may not be pre-fetched when mail arrives in the Promotions tab, unlike emails that land in the Primary inbox. This distinction could have profound implications for email tracking and the perceived effectiveness of campaigns.
This subtle but significant difference in image loading (or lack thereof) helps explain discrepancies in open rate data, especially for promotional content. We've seen instances where marketers report a 10-20% drop in open rates for emails routed to the Promotions tab, yet their revenue and conversion metrics remain consistent. This disconnect points to pre-fetching as a key factor distorting traditional open tracking.
Understanding Gmail image pre-fetching
To understand why this pre-fetching behavior might differ, it helps to first grasp how Gmail image pre-fetching generally works. When an email arrives in a user's Primary inbox, Gmail typically loads and caches images on its servers before the user even opens the email. This process serves multiple purposes, including enhancing user privacy by masking the recipient's IP address from the sender's server and improving the user experience by displaying images instantly upon opening.
However, this pre-fetching also inadvertently triggers the tracking pixels embedded in emails, leading to inflated open rates. For years, email marketers have relied on open rates as a primary metric, often unaware that many of these 'opens' were automated fetches by mailbox providers, not actual human engagement. This has been a long-standing challenge in accurately measuring email campaign performance.
The distinction in pre-fetching behavior between the Primary and Promotions tabs could be attributed to several factors. It might be a strategic decision by Google to differentiate how it handles various types of email content, aligning with its overall goal of providing a more organized inbox experience. Promotional emails are already categorized, and perhaps the urgency for instant image loading is reduced in a tab designed for less immediate interaction.
The functional divide: Promotions vs. primary
Gmail's tabbed inbox, introduced in 2013, automatically categorizes incoming emails into tabs like Primary, Social, Promotions, Updates, and Forums. While the Promotions tab is often viewed with skepticism by marketers, it serves a specific purpose: to organize marketing emails, newsletters, and offers into a dedicated space. This organization can actually benefit users by reducing clutter in their primary inbox and making promotional content easier to find when they are ready to engage with it. For more details on this, you can read our article, Should promotional emails go to Gmail's primary or promotions tab?.
The key difference in image pre-fetching likely stems from the intended user experience of each tab. The Primary tab is designed for personal and important communications, where immediate and full rendering is paramount. Conversely, the Promotions tab is for content that users might browse at their leisure. If Google avoids pre-fetching images for emails in the Promotions tab, it could be a resource optimization strategy, saving bandwidth and processing power for content deemed more critical.
Additionally, the Promotions tab offers unique features, such as Gmail Promotions Annotations, which allow marketers to display featured images, deals, and expiration dates directly within the inbox view, even before an email is opened. This functionality acts as a carrot for marketers, encouraging them to optimize for this tab rather than trying to avoid it entirely. These annotations are rendered via Schema markup, and do not rely on standard image loading for their display.
Impact on metrics and deliverability
The differing pre-fetching behavior in the Promotions tab has significant implications for how marketers should analyze their campaign performance. If images are not pre-fetched, then the reported open rates for emails in this tab will be a more accurate reflection of actual human engagement, as opposed to automated system interactions. This means a lower open rate in the Promotions tab doesn't necessarily indicate a lack of interest, but rather a more truthful count of unique human opens. We discuss this more in our article How does the Gmail promotions tab affect email open rates?.
This insight highlights the ongoing challenge of relying on open rates as a sole measure of email success. Factors like Gmail's own pre-fetching, as well as other privacy features like Apple Mail Privacy Protection, have made open rates less reliable over time. Instead, marketers should shift their focus to more definitive engagement metrics, such as click-through rates, conversions, and direct revenue attribution.
Primary inbox pre-fetching behavior
Image loading: Images are typically pre-fetched and cached by Gmail servers upon delivery, even before the user opens the email.
Open rate impact: Leads to inflated open rates due to automated pixel firing, making it harder to gauge true human engagement.
User experience: Aims for immediate image display for a seamless experience in a tab for high-priority mail.
Promotions tab pre-fetching behavior
Image loading: Images may not be pre-fetched; they load only when the user explicitly opens the email.
Open rate impact: Provides a more accurate, albeit lower, representation of actual human opens.
User experience: Less emphasis on instant image display, aligning with the tab's purpose for curated promotional content.
Adapting your email strategy
Given these distinctions, how should marketers adapt their strategies? First, it is important to acknowledge that whether an email lands in the Primary or Promotions tab is largely determined by Gmail's algorithms, which analyze content, sender reputation, and user engagement. While some best practices can influence placement, trying to force emails into the Primary tab may not always be the most effective approach. Sometimes, the Promotions tab is where users expect to find marketing messages, making them more receptive to your content.
Rather than focusing on where an email lands, prioritize creating engaging content that drives clicks and conversions, regardless of the tab. Embrace the Promotions tab by utilizing Gmail's Promotions Annotations to make your emails stand out. These annotations offer a valuable opportunity to provide visual previews and key information that can entice users to open. Additionally, focus on optimizing image sizes to ensure quick loading for all recipients, no matter where your email lands. Email image sizes can affect deliverability.
Ultimately, the shift in image pre-fetching behavior underscores the need to evolve how we measure email success. Move beyond vanity metrics like open rates and focus on metrics that truly reflect customer action, such as click-through rates, conversion rates, and revenue generated. This approach will provide a more accurate picture of campaign effectiveness and allow for better optimization strategies.
Views from the trenches
Best practices
Focus on optimizing email content for clicks and conversions, rather than just open rates.
Implement Gmail Promotions Annotations to enhance visibility and engagement within the tab.
Regularly monitor deliverability to ensure emails are reaching the intended inboxes consistently.
Segment your audience and tailor content to improve engagement and reduce spam complaints.
Common pitfalls
Over-reliance on open rates as a primary metric for campaign success due to pre-fetching.
Aggressively trying to bypass the Promotions tab, which can negatively impact sender reputation.
Neglecting email authentication standards like SPF, DKIM, and DMARC.
Sending inconsistent email volumes, which can trigger spam filters and blocklists.
Expert tips
Utilize Google Postmaster Tools to gain deeper insights into your deliverability and reputation.
Perform A/B testing on calls-to-action (CTAs) and subject lines to optimize engagement.
Clean your email lists regularly to remove inactive subscribers and reduce bounce rates.
Consider engaging with recipients immediately after they subscribe to build positive interaction.
Expert view
Expert from Email Geeks says that Google's theory about not pre-fetching images when mail lands in the Promotions tab, but doing so when it's in the inbox, provides a clear explanation for observed data where open rates drop significantly in the Promotions tab while revenue remains consistent.
2021-11-05 - Email Geeks
Marketer view
Marketer from Email Geeks says that if Gmail does not pre-fetch in the Promotions tab, it implies more accurate open rates for senders landing there, but it also seems inefficient given those images would require rendering upon opening.
2021-11-05 - Email Geeks
Key takeaways
The theory that Google pre-fetches images differently in the Promotions tab compared to the Primary inbox provides a compelling explanation for the observed discrepancies in email open rates. This nuance highlights the evolving landscape of email marketing metrics and the need for marketers to adapt their measurement strategies. By understanding these technical distinctions, you can gain a clearer picture of your audience's true engagement and build more effective campaigns.
Ultimately, deliverability is not just about avoiding the spam folder or manipulating tab placement. It is about consistently reaching your audience with valuable content that drives meaningful interactions. Focusing on genuine engagement metrics and leveraging tools like Google's own features for promotional emails will lead to more sustainable success.
