Email Header Dimensions

Recommended size: 600 × 200 pixels

600 × 200
3:1

Email header images are typically 600×200 pixels at a 3:1 aspect ratio. The 600px width is the long-standing email design standard because most email clients render content within a 580-640px container. Email images face unique challenges: many clients block images by default, some strip background images entirely, and file size directly impacts deliverability. Every extra kilobyte increases the chance your email lands in the Promotions tab or gets flagged by spam filters.

Specifications

Width 600px
Height 200px
Aspect Ratio 3:1
Platform email
Category marketing

Why 600px Width Is the Standard

The 600px email width dates back to Outlook and Hotmail rendering constraints, but remains relevant:

  • Gmail desktop: Renders emails at approximately 632px container width
  • Outlook desktop: Default reading pane is approximately 580-640px depending on layout
  • Apple Mail: Variable, but 600px fits all standard configurations
  • Mobile clients: Images scale down to screen width (~390px) — a 600px image downscales cleanly

Images wider than 600px will be clipped in some clients (notably Outlook) or cause horizontal scrolling. Retina optimization tip: design at 1200×400 and set the display dimensions to 600×200 in your HTML — this provides sharp 2× resolution on Retina/HiDPI screens without layout issues.

Image Blocking and Alt Text Strategy

Many email clients block images by default until the user clicks "Show images":

  • Outlook: Images blocked by default in corporate environments
  • Gmail: Usually shows images (for trusted senders), but may block for new/unknown senders
  • Apple Mail: Shows images by default

This means your email must make sense without images. Strategies:

  • Always include descriptive alt text for every image
  • Style your alt text with inline CSS — font-size, color, font-family work in many clients
  • Never put critical information (discount codes, deadlines, CTAs) only in images
  • Use HTML text for your primary message and images for visual enhancement
  • Keep your header image decorative rather than informational

File Size and Deliverability Impact

Email file size directly affects deliverability:

  • Gmail clips emails over 102 KB (total HTML size) — images loaded externally don't count toward this, but inline/embedded images do
  • Large total email sizes can trigger spam filters
  • Slow-loading images hurt engagement metrics, which affect sender reputation

Optimize email images aggressively:

  • Target under 50 KB per image, under 200 KB total for all images in the email
  • Use JPEG at quality 60-75 for photographs (more compression than web — email images are viewed briefly)
  • Use PNG-8 (not PNG-24) for graphics with limited colors
  • Consider removing the header image entirely — many high-performing emails use text-only headers

Quick Tips

  • → Design at 1200×400 and display at 600×200 for Retina sharpness
  • → Keep total email image weight under 200 KB for deliverability
  • → Always include styled alt text — many clients block images by default
  • → Never put critical info (promo codes, CTAs) only in images

Frequently Asked Questions

What size should email header images be?

600×200 pixels for standard displays, or 1200×400 for Retina/HiDPI (displayed at 600×200 via HTML width attribute). The 600px width ensures compatibility with all major email clients including Outlook and Gmail. Keep file size under 50 KB for optimal deliverability.

Do email clients block images?

Yes. Outlook blocks images by default in many corporate configurations. Gmail usually shows images for trusted senders but may block them for new or untrusted senders. Apple Mail shows images by default. Always include alt text and ensure your email's key message is conveyed through HTML text, not just images.

Should I use PNG or JPEG for email images?

Use JPEG at quality 60-75 for photographs — more aggressive compression is acceptable in emails since they're viewed briefly at small sizes. Use PNG-8 for graphics with few colors, logos, and icons. Avoid PNG-24 for email — the file sizes are too large. GIF is supported for simple animations but keep them under 200 KB.