Why Image Size Matters for Email

Email has much stricter constraints than the web. Most email clients load images over cellular connections, inbox filters penalise large messages, and many corporate email servers reject attachments over 10 MB. For email marketing specifically, large images cause slow rendering and increase bounce rates — hurting your deliverability reputation over time.

Target file sizes for email images: under 100 KB for email marketing images, under 200 KB for direct attachments, total email size (HTML + images) under 1 MB.

The Right Dimensions for Email Images

Most email clients render content in a column 600–700 px wide. Using images wider than this is pure waste — the client scales them down to fit anyway. Recommended maximum widths:

  • Header / banner image: 600 × 200 px (600 px wide maximum)
  • Product image in email: 200–300 px wide per column
  • Email signature logo: 150–200 px wide
  • Full-width promotional image: 600 × 300 px

Resize to these dimensions before compression using our Image Resizer.

Step-by-Step: Prepare Images for Email

  1. Resize first: Use our Image Resizer to resize to your target email dimensions (maximum 600 px wide for most images)
  2. Choose the right format: Use JPG for photographs. Use PNG for logos and graphics with text or transparency.
  3. Compress aggressively: Use our Image Compressor at 75–80% quality for email images — the small display size means quality loss is less noticeable
  4. Check final size: Aim for under 100 KB per image, under 50 KB for small product thumbnails

Using Hosted Images vs Inline Attachments

For email marketing campaigns (Mailchimp, Klaviyo, etc.), always host images on a server and reference them with URLs — never attach images to marketing emails. Email marketing platforms do this automatically when you upload images to their media libraries.

For direct email attachments (sending a photo to a client), compress the image first and keep the total attachment size under 10 MB to avoid rejection by corporate mail servers.

Inline Base64 Images in Email HTML

Some HTML emails embed small images as Base64 data URIs. This ensures images display even when the recipient's email client blocks external images. Use this technique for logos and small decorative elements only — large Base64 images increase email size dramatically and hurt deliverability.

Convert small logos and icons to Base64 using our free Image to Base64 Converter.

Quick Email Image Checklist

  • ☑ Maximum 600 px wide
  • ☑ Under 100 KB per image
  • ☑ JPG format for photographs
  • ☑ PNG for logos and transparent elements
  • ☑ Always include alt text (many clients block images by default)
  • ☑ Host images externally for marketing emails
  • ☑ Total email size under 1 MB