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Signature Size

Email Signature Size: Dimensions & Image Guide

Optimal sizes for logos, banners, and headshots

An oversized email signature slows loading, triggers spam filters, and looks broken on mobile. Too small, and it is unreadable. This guide covers the exact dimensions, file sizes, and formatting specifications for every element of a professional email signature.

Recommended Overall Signature Dimensions

  • Maximum width: 600-650px — This fits within most email client preview panes without horizontal scrolling.
  • Maximum height: 150-200px — Taller signatures push your email content down and feel intrusive.
  • Text lines: 3-5 lines of text maximum. More than 7 becomes excessive.

Image Size Guidelines

Company Logo

  • Width: 100-200px (150px is ideal)
  • Height: 40-80px (maintain aspect ratio)
  • File size: Under 10KB for best loading speed
  • Format: PNG for logos with transparency, JPG for photos. Avoid GIF and BMP.
  • Resolution: 2x for retina displays (e.g., 300px wide displayed at 150px)

Headshot / Profile Photo

  • Dimensions: 80x80px to 100x100px (square or circular)
  • File size: Under 15KB
  • Format: JPG at 70-80% quality for best size-to-quality ratio
  • Tip: Use a professional headshot. Casual photos undermine your brand.

Social Media Icons

  • Dimensions: 20x20px to 24x24px
  • File size: Under 2KB each
  • Format: PNG with transparency
  • Spacing: 8-12px between icons

CTA Banner

  • Width: 400-600px (full width of signature)
  • Height: 60-100px
  • File size: Under 30KB
  • Format: JPG or PNG. Use JPG for photo-based banners, PNG for graphic designs.

Total Signature File Size

Your entire email signature (all images combined) should be under 50KB. Ideally under 30KB. Large signatures:

  • Slow down email loading, especially on mobile networks
  • Can trigger spam filters in some email systems
  • Get blocked by corporate email security policies
  • Show as attachments in some clients (especially Outlook)
  • Consume recipients' data and storage

Image Hosting Best Practices

How you host your signature images affects deliverability and rendering:

  • Use hosted URLs: Link to images on your website or CDN rather than embedding them. This keeps email size small.
  • Use HTTPS: Some email clients block HTTP images. Always use HTTPS URLs.
  • Avoid embedding: Base64-encoded or attached images increase email size significantly and often show as attachments.
  • Add alt text: Include alt attributes on all images. When images are blocked, the alt text still conveys information.

Testing Your Signature Size

  1. Send a test email to yourself at multiple email addresses (Gmail, Outlook, etc.).
  2. Check on both desktop and mobile.
  3. Verify images load correctly and are not showing as attachments.
  4. Check that text is readable without zooming on mobile.
  5. Confirm the total email size is reasonable (check sent folder → message details).

For design tips, see best signature fonts and signature ideas. For setup guides, visit Outlook, Gmail, and iPhone.

Explore more: email signature examples, how to end an email, and AI email tools.

Explore all guides in this series: email signature guide, Outlook signature, Gmail signature, student signature, teacher signature, signature ideas, best fonts, iPhone signature, business owner signature, what is a signature.

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