Images

Signature images - company logos, campaign banners and profile photos - come from three sources in SignatureCat: the built-in image library, external URLs you host yourself, and Google Directory profile photos. This page is the reference; the practical guide is Banners and logos.

The image library

Each workspace has one library with two kinds of entries:

Library entries carry an optional label, an optional click-through link and an optional Image description (ALT). Each template selects its own logo and banner from the library; templates without a selection render a neutral placeholder. Uploads are PNG, JPG or GIF - up to 5 MB for PNG/JPG and 20 MB for GIF (200 KB recommended for static images); SVG is not accepted.

Image description (ALT)

The Image description (ALT) is what a recipient sees instead of the picture when their mail client blocks images, and what a screen reader announces. It is optional and limited to 300 characters.

• Where you set it: in the add form when you upload a file or paste a link, in the image step of the new-template wizard, and later in the Selected image details panel of the library.
• What it applies to: every library entry, whether SignatureCat hosts the file or you link to your own.
• Where it travels: with the library entry, exactly like the click-through link - change it once and every template using that image ships the new description on the next render.
• If you leave it empty: the image is rendered as decorative and gets no description.

Where images are served from

• Library uploads are stored by SignatureCat and served from https://images.signature.cat/... over a CDN with long-lived caching.
• With a verified custom image domain, newly rendered signatures serve library images from your subdomain (for example images.yourcompany.com) instead - better deliverability, same storage.
• External URL images ("I have a link") are hot-linked from wherever you host them. They must be public and HTTPS; ideally host them on your own domain.

Profile photos

The {{photo}} variable uses the user's Google profile photo from Directory (auto-scaled to 400 px). It is not part of the library - users and admins manage profile photos in Google Workspace. See Template variables.

Lifecycle notes

• Replacing an image: upload the new file, select it on every template that used the old one, and delete the old entry only once you are sure - or keep the same library entry and only update its click-through link or ALT description, which every template picks up on the next render.
• Deleting a library entry detaches it from templates that use it (they fall back to the placeholder) after a warning with the usage count. Those signatures keep applying in the meantime.
• Deleting an in-use image notifies the workspace: an in-app notification appears in the bell and an email goes to the admins and the owner, naming the affected templates. See Notifications.
• Hosted files are released: once the library entry is gone, SignatureCat cleans up the stored file on the next daily pass, so the image stops loading in already-delivered emails too. Deletion is permanent and there is no self-service undo.
• External images are unaffected by deletion. You host the file, so removing the library entry only removes the entry - old emails keep loading the image until you take it offline yourself.

Deliverability tips

• Keep files small (banners under 200 KB) - large images slow rendering and hurt spam scores.
• Serve images from your own domain with a custom image domain - mail clients trust the sender's domain more.
• Gmail proxies images for recipients, so exotic hosting setups (IP allowlists, referer checks) will break rendering. Keep images plainly public.