A slow-loading email newsletter kills click-through rates. Images are the biggest culprit. The average newsletter contains 3–8 images, and if each one weighs 500 KB, your email is over 4 MB before you add any text. Most email clients timeout or clip the message at around 102 KB. Here's how to get your newsletter images small enough to load fast without looking terrible.

Why image size matters in email

Email clients (Gmail, Outlook, Apple Mail) don't load images immediately — they wait for the recipient to click "show images" or scroll. Heavy images mean a long wait. Gmail clips emails over 102 KB, hiding the rest behind a "view entire message" link, which dramatically hurts engagement. Mobile users on slow connections feel the pain most: a 1 MB hero image takes 8+ seconds on a 1 Mbps mobile connection.

Target file sizes for newsletter images

Hero image: under 100 KB (200 KB maximum).
Product images: 30–80 KB each.
Icons and logos: 5–20 KB.
Total email image payload: under 500 KB.

Recommended pixel dimensions

Email newsletter content columns are typically 600 px wide. Use these dimensions as a starting point:

Hero/header banner: 600 × 200 px or 600 × 300 px
Full-width product image: 600 × 400 px
2-column product grid: 280 × 280 px per image
Logo: 200 × 60 px (or match your brand's proportions)

Don't upload a 2000 px wide image and let the email client scale it down. It still downloads the full-resolution file. Resize to the actual display dimensions before uploading to Mailchimp, Klaviyo, or whichever platform you use.

Choosing the right file format

Email clients have spotty WebP support (Gmail supports it; Outlook 365 does not). Stick to JPEG for photos and PNG for graphics with transparency or text overlays.

JPEG at 80% quality: photos, product shots, lifestyle images.
PNG-8 or PNG-24: logos, icons, images with transparent backgrounds.
Avoid GIF for still images — the palette limit makes photos look terrible.

How to compress newsletter images

Use our Image Compressor to reduce file size before uploading to your ESP. Drop your hero image in, set quality to 80–85%, and download. A typical 4 MB phone photo becomes 80–120 KB with no visible quality loss at newsletter dimensions.

For batch compression of a product catalog: use our Image Resizer first to hit 600 px width, then compress. This two-step process reliably produces images under 100 KB.

Mailchimp image upload limits

Mailchimp's file manager accepts images up to 10 MB per file, but their Image Editor has a 3 MB limit. More practically, Mailchimp recommends keeping newsletter images under 1 MB each and total campaign size under 500 KB. Klaviyo recommends images under 1 MB and total email size under 200 KB for best deliverability.

Retina display considerations

Most email clients on modern phones use 2× or 3× pixel density. A 600 px wide image looks blurry on a Retina display. The solution: upload at 1200 px wide, but set the HTML width attribute to 600 px so it displays at half size. The download is larger, but on mobile connections email clients cache images aggressively — the extra size is usually worth the sharpness.

Testing before sending

Always send a test to yourself and open it on Gmail (web), Apple Mail, and Outlook before hitting send. Check: do images load? Is the file size reasonable? Are any images blurry on your phone? Tools like Litmus or Email on Acid show render previews across 90+ clients, but a quick personal test catches 80% of issues.