Email Signature Size: Image Dimensions and Format That Work in Gmail and Outlook

Quick answer: keep each image in an email signature about 70 to 100 pixels high (Google recommends 70 to 100 high by 300 to 400 wide, with a maximum of 100 by 1,000), keep the whole signature 600 pixels wide or less, and use PNG or JPG. The rest of this guide explains why, and what changes in Outlook.

A signature that looks perfect in your own inbox can fall apart in someone else's: a logo that is too big, a banner that never loads, a transparent image that disappears in dark mode. This guide sticks to what Google, Microsoft and the email-testing community actually document, and says so where there is no official number.

Sizes: what Gmail says, and a safe overall width

Google recommends signature images about 70 to 100 pixels high and 300 to 400 pixels wide, with a maximum of 100 pixels high by 1,000 pixels wide. There is no official width standard for a whole signature. Email templates commonly use about 600 pixels as a maximum width (Campaign Monitor's guidance, which is for emails rather than signatures), so keeping a signature at 600 pixels wide or less is a reasonable, safe choice.

Set width and height on every image

Litmus notes that Outlook does not support CSS styles for widths and heights, and if you do not set width and height attributes it shows the image at its actual size. So a large logo you shrank with styling can appear huge in Outlook. Set explicit width and height on each image, and export the image at about twice the displayed size so it stays sharp on high-resolution screens.

Hosted or embedded images

Hosted images load from a web address. Outlook blocks automatic picture downloads by default, so recipients may have to click to see them. Embedded images travel inside the email and usually display, but they can show up as attachments, which looks messy and can bloat every message. Either way, do not put critical information (your name, title, phone number) only inside an image.

PNG or JPG, not SVG

Use PNG or JPG. SVG support in email is inconsistent: Can I Email reports Gmail on the web rasterizes SVGs to PNG, that Gmail's mobile apps support them only for non-Google accounts, and that several versions of Outlook on Windows do not support them at all. PNG works everywhere.

Animated GIFs

Desktop Outlook on Windows uses Word's rendering engine. Litmus advises making the first frame of a GIF carry the message you want, since some Outlook versions show only that frame. Can I Email adds that newer Microsoft 365 builds may play the animation a few times, so treat animation as a bonus and never as the only way to get your point across.

Dark mode

In dark mode, a logo with dark text on a transparent background can vanish. Litmus recommends adding a light outline or glow to transparent PNGs with dark text, or supplying separate light and dark versions of a logo. Litmus's 2022 email client data put dark mode use at an average of 35 percent, so it is worth a quick check.

Email handtekening formaat · taille d'une signature de mail

E-mail handtekening formaat: Google adviseert afbeeldingen van ongeveer 70 tot 100 pixels hoog en 300 tot 400 pixels breed; het maximum is 100 pixels hoog en 1.000 pixels breed. Houd de hele handtekening op 600 pixels breed of minder, gebruik PNG of JPG en geef elke afbeelding een alt-tekst.

Taille d'une signature de mail : Google recommande des images d'environ 70 à 100 pixels de haut et de 300 à 400 pixels de large, avec un maximum de 100 pixels de haut sur 1 000 de large. Gardez la signature entière à 600 pixels de large ou moins, utilisez le PNG ou le JPG et ajoutez un texte alternatif à chaque image.

A quick checklist

• Images no taller than 100 pixels, whole signature 600 pixels wide or less.
• PNG or JPG, with width and height set on each image.
• Alt text on every image, and key details also in plain text.
• Transparent logos checked in dark mode, with an outline if needed.
• If you use an animated GIF, make the first frame stand on its own.
• Send yourself a test to Gmail and Outlook before rolling it out.