Image Blocking
When email clients do not display images by default, requiring users to manually enable them.
Definition
Image blocking is when email clients do not load or display images in emails by default. Recipients see placeholder boxes or alt text instead of images until they choose to enable images. This is a privacy and security feature - images can track opens and potentially deliver malware. Many corporate email systems and some webmail providers block images by default.
Why It Matters
Image blocking affects both the visual experience and your metrics. Emails designed with image-heavy layouts look broken when images are blocked. Open tracking pixels do not fire until images load, making open rate data incomplete for image-blocked recipients. Design with image blocking in mind.
How It Works
Email clients intercept image requests when rendering emails. Instead of loading remote images, they display placeholders. Users can enable images for individual emails or whitelist senders. When images load, your tracking pixel fires, registering an open. Without image loading, opens go untracked.
Best Practices
- 1Design emails that communicate clearly even without images
- 2Use descriptive alt text on all images
- 3Do not rely on images alone for critical information
- 4Maintain good text-to-image balance
- 5Use background colors to maintain design structure without images