Design & best practices

Email Signature Size Guide

There is no universal pixel size for every signature. Use these ranges as starting points, then test the actual content in the email clients your recipients use.

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ElementStarting rangeWhy
Total width320–600 CSS pxFits many desktop and narrow inboxes.
Logo100–220 CSS px wideIdentifies the business without dominating.
Headshot64–120 CSS px squareRecognisable while leaving room for text.
Banner300–600 CSS px wideKeeps a short campaign within the signature width.

Choose width for the content

A text-only design can be narrower than one with a portrait and banner. Check long names, phone numbers and addresses at 375px and 390px. Shorten or rearrange details if the message scrolls horizontally.

File size, resolution and retina displays

Crop before uploading. A 2,000-pixel source displayed as a 100-pixel logo wastes bytes. Export near twice the display dimensions for high-density screens and compress the result. Small logos and portraits can often be kept in the tens of kilobytes; inspect quality rather than enforcing one file limit.

PNG, JPG, GIF and WebP

PNG suits transparent logos and crisp edges. JPG is often efficient for photographs. An animated GIF needs a useful first frame because animation may not play. WebP support varies between email clients, so PNG or JPG is a safer choice for mixed audiences.

Mobile layout

Keep text lines short and avoid a layout that requires responsive CSS to remain readable. A compact vertical arrangement often survives a narrow inbox better than rigid columns. Test both image-loaded and image-blocked states.

Image hosting

Use public HTTPS URLs, not local files or private links. Give images width and height, and keep the host reliable. If remote images are blocked, the sender name and contact details must still be readable.

Outlook and Gmail checks

Classic Outlook can alter spacing and image scale; new Outlook may differ. Gmail may change pasted markup. Send a real message from the installed signature and inspect it in both environments. The best-practices guide and templates provide context.

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