Email Signature Logo Size: Gmail and Outlook Setup Without Broken Images

Recommended email signature logo sizes

Why so small? A signature sits under every message, often several times in a reply thread. A 600 px logo dominates the email, pushes the actual message off screen on phones, and looks like marketing rather than a signature. Your name and phone number should be the most prominent part.

Why export at 2×? Most phones and many laptops have high-density screens. A 200 px wide image drawn on a retina display uses 400 physical pixels; if the file is only 200 px, it is enlarged and looks soft. Export at double and tell the email client to display it at the smaller width.

Hosted image vs pasted image

There are two ways to put a logo into a signature, and they behave very differently:

• Hosted (linked) image: the signature contains an <img> pointing to a URL such as https://yourdomain.com/email/logo.png. The recipient’s app downloads it when the email opens. Messages stay small, the logo never shows as an attachment, and you can update the logo later by replacing the file. Some recipients see “images blocked” until they allow images from you.
• Embedded (pasted/uploaded) image: the image is attached to every email inline. It displays even with images blocked in some apps, but it increases message size, often appears as an attachment (the paperclip icon), and gets stripped or mangled when messages are forwarded.

For business email we recommend hosted. Upload the logo to your own website (for example a /email/ folder) so the URL stays stable. Avoid hosting on personal Google Drive or Dropbox share links — they are not direct image URLs and often break.

Adding a logo in Gmail

1. In Gmail on the web, click the gear icon → See all settings → General → Signature → Create new.
2. Either build the signature directly — click the image icon and choose Web Address (URL), then paste your hosted logo URL — or build it in the Email Signature Generator and paste the whole signature into the box.
3. Click the image in the editor to choose Small, Medium, Large or Original size. If you exported at 2× and the logo looks too big, use Small or Medium; better, set the width in the generator before pasting.
4. Set the signature defaults for new emails and replies, then Save Changes at the bottom.

Gmail signatures are limited to 10,000 characters. Pasting an image directly (rather than a URL) can exceed that, which is why Gmail sometimes shows “signature is too long”. The Gmail mobile apps use a separate plain-text signature and do not show images — messages sent from the phone app use the web signature only if you turn off the mobile one.

Adding a logo in Outlook

New Outlook for Windows and Outlook on the web: Settings → Accounts → Signatures → New signature. Paste the signature from the generator, or use the image button to insert the logo. Set it as default for new messages and replies.

Classic Outlook for Windows: File → Options → Mail → Signatures. Paste the signature. Classic Outlook embeds images by default.

Outlook for Mac: Outlook → Settings → Signatures.

The Outlook DPI scaling issue

Classic Outlook on Windows scales images according to the computer’s display scaling (125%, 150%) when the image has no explicit width and height. A 400 px logo you intended to show at 200 px can appear at 400 px — or larger. Always give the image explicit width and height attributes in the HTML (the generator does this). If you insert the image manually, resize it inside the signature editor rather than relying on the file’s pixel size.

Dark mode: the invisible-logo problem

Apple Mail, Outlook and Gmail apps can display emails in dark mode, and some invert light backgrounds to dark. A dark logo on a transparent background then sits on near-black and disappears. Options:

• Solid white background in the PNG itself (not transparent). Some apps still darken it, but the logo remains visible.
• A thin light outline or glow around a dark logo — subtle in light mode, lifesaving in dark mode.
• Test: send to yourself and view in dark mode on iPhone Mail and Outlook before rolling it out to the whole team.

Formats that work (and those that do not)

• PNG: best for logos — crisp edges, optional transparency.
• JPG: fine if the logo has a solid background; keep quality at 85+ to avoid smudged edges.
• GIF: works everywhere, but limited to 256 colours; animated GIFs are distracting and Outlook desktop shows only the first frame.
• SVG: not supported by Gmail or Outlook — the image will not appear.
• WebP: support is inconsistent across email apps; avoid in signatures.

Fixing common signature logo problems

If the file is heavy, the Image Compressor can hit a target size in KB; our guide to fixing oversized logo files explains what to change first.