What is the best image size for a Gmail signature logo?

Export the logo at twice the displayed width. If it will be shown at 120 pixels wide, export at 240 pixels wide. Keep the file under 50 KB if possible.

Should I use PNG or JPG for my email signature image?

Use PNG for logos with flat colours and transparency. Use JPG for headshot photos with gradual tones. JPG usually gives a smaller file size for photos.

Why does my email signature logo look blurry?

The image may be too small for the display size. Export at twice the displayed width so high density screens can scale it down cleanly.

How do I test my signature in dark mode?

Send a test email to yourself and open it in an email client that supports dark mode. Check that transparent areas of a PNG logo do not become invisible on a dark background.

Email Signature Images: Size, Format and Compression

Email signature images have to be sharp and they have to be small. The file gets attached to every message you send, so its weight multiplies across your outbox. Get the email signature image size and format right and your logo or headshot stays crisp. No bloated messages. No blocked images. Here are the dimensions, file types, and compression choices that work for logos, headshots, and Gmail signatures.

Choose the Right Format PNG or JPG

Logos Use PNG

Logos with flat colours and sharp edges work as PNG. PNG supports transparency, so the logo sits cleanly on coloured or dark email backgrounds.

Headshots Use JPG

Headshot photos have gradual tones and subtle shading. They compress better as JPG. A JPG will be smaller than a PNG for a photo of the same dimensions. For photos, set JPG quality to a level that balances sharpness and size.

Compress a logo further by saving it as PNG with 8-bit colour. That often cuts file size noticeably while keeping the logo crisp.

Set the Right Dimensions for Sharpness

Email clients display signature images at a fixed pixel width. Export at twice the displayed width to keep the image sharp on high-density screens. The extra pixels let the browser scale the image down cleanly. No blurry logo.

For headshots, export at twice the displayed width for the same reason. Total file size stays low because the pixel count is still modest.

Why File Size Matters for Email

Every email you send attaches the signature image. The recipient downloads it. Some email clients block images until the reader allows them. If your signature relies entirely on the image, the email looks empty or broken. Write out your name, title, and contact information as text. The message stays readable even when images are blocked.

Large attachments punish recipients on mobile data plans or slow connections. Keep the file small.

Gmail Signature Settings and Limits

Where to Add It

In Gmail, go to Settings > See all settings > General > Signature. The signature editor has a 10,000 character limit. That limit includes the raw HTML of any inserted image.

Resize Before You Paste

If you paste a very large image, Gmail scales it down for display. The full file size is still downloaded by every recipient. A heavy logo slows down email loading for everyone you write to, even if it looks small in the message. Resize and compress the image before adding it. Keep the file as small as possible if you can, and under a certain limit at most. Test by sending an email to yourself and checking the download size in your email client.

Handle Transparency and Dark Mode

Transparent PNG logos can vanish in dark mode. If the email client uses a dark background, a transparent area in the logo lets that dark colour show through. The logo becomes unreadable. Test your signature in both light and dark modes before finalising it. If the logo looks fine on white but disappears on black, add a small solid background colour to the image. Or use a version with a white or light background.

For headshots, a rectangular crop with a solid background is safer than a cut-out shape with transparency. The same test applies. Send a test email and view it in a dark mode preview.

Step by Step Prepare Your Signature Image

Open your logo or headshot in any image editing software.
Resize the image to twice the displayed width. Keep the height proportional.
For a logo with flat colours, save as PNG with 8-bit colour. For a headshot, save as JPG with quality set to a level that balances sharpness and size.
Check the file size. If it is above a certain threshold, reduce the pixel dimensions slightly or lower the JPG quality to a lower percentage.
Upload the image to your email client or paste it into the signature editor.
Send a test email to yourself. View it on a phone, a desktop, and in dark mode if your client supports it.

Final Checks Before You Save

Before you finalise your email signature, confirm the image is sharp at normal viewing size and the file is under a certain limit. To compress the logo further, reduce colour depth or lower JPG quality in small steps. After saving, send another test email. Check that the signature looks correct and that the text-based information is still present. A tool like tinyimgcompress.com can reduce file size quickly while keeping dimensions under control.