Email Signature Images and Logos: Size and Display
How to prepare a vector logo for an email signature: why signatures need raster exports, how to size and format the image, and how to keep it legible across clients and dark mode.
Contents
The Short Answer
An email signature logo should usually be a small raster image exported from your vector master file, not the vector file itself. Vector formats such as SVG, AI, EPS or vector PDF are the right place to keep and edit the artwork. Many widely used email clients, however, do not reliably render SVG in a message body, so the signature itself needs a PNG, JPG or GIF preview of the logo. Choose its size by how it will appear next to your name and contact details, not by the dimensions of the original artwork.
The supplied material contains no confirmed pixel dimensions, file-size limits or per-client specifications. This article therefore does not recommend exact numbers. Before you settle on a size, check the current documentation for your signature tool and the email clients your recipients use.
Vector Artwork, Embedded Rasters and Raster Previews
Three kinds of file often get confused when people prepare a signature logo:
- Vector artwork: the logo is built from editable paths and shapes, so it can be scaled without losing quality. It is the master source for every other version.
- Embedded raster images: a pixel image placed inside a vector-format file. A file ending in .svg, .eps or .pdf may contain only a pasted bitmap and no editable paths, so you cannot judge this from the filename or extension.
- Raster previews: PNG, JPG or GIF exports of the artwork at a fixed pixel size. This is the version that goes into an email signature.
Before you export, open the source file in a vector editor and confirm the logo consists of real paths. If it is only an embedded bitmap, your signature image can be no sharper than that bitmap. Rebuilding or obtaining true vector artwork would be the better starting point.
Choosing a Format for the Signature Image
| Format | Typical use in a signature | Points to watch |
| PNG | Logos with flat colour, sharp edges or transparency | Transparent areas take on the recipient's background, which can hide dark artwork in dark mode |
| JPG | Photographic headshots or complex imagery | No transparency; compression can blur the edges of logos and text |
| GIF | Simple animation, where it is used at all | Limited colour palette; some clients show only the first frame |
| SVG | Keep as the vector master, not for sending | Rendering in email clients is inconsistent and often unsupported |
How Size Affects Display
Two separate sizes matter. The display size is how large the logo appears in the message. The pixel size is how many pixels the exported file contains. Many people export at a multiple of the intended display size, commonly double, and then set the width in the signature's HTML. This keeps the logo sharp on high-density screens. It only works if the signature tool or the client respects the width setting; if it doesn't, the oversized image may display at full size.
Keep the file weight modest as well. A heavy image slows loading and can make the signature look intrusive. If the image is attached rather than hosted, it also adds to the size of every message you send.
Keeping the Logo Readable in Real Inboxes
- Some clients block remote images by default, so put your name, role and contact details in live text rather than inside the image.
- Add short, descriptive alt text so recipients who see no image still know what it was.
- Test the logo against both light and dark backgrounds. A transparent PNG with dark artwork can disappear in dark mode, so consider a light outline, padding or a solid background in the export.
- Simplify for small sizes. Fine taglines and thin strokes that work in the full lockup may become illegible, so a compact mark or simplified version may suit a signature better.
- Decide whether the image will be hosted at a stable location or embedded in each message. Hosted images depend on that location staying available, while embedded or attached images can appear as attachments in some clients.
Permission to Use the Logo
Being able to download a logo file does not mean you may modify it. Using a company's logo in a staff signature is normally covered by internal brand guidelines. Recolouring it, cropping it, adding outlines for dark mode or swapping its typeface may need separate approval, especially where trademarks or licensed fonts are involved. If you are preparing signatures for an organisation, confirm which logo versions are approved for email and whether small-size or dark-background variants already exist.
Gaps in the Available Evidence
The supplied material does not establish recommended pixel dimensions, maximum file sizes, or how individual email clients and signature platforms currently handle scaling, dark mode or SVG. Treat those details as things to verify in current vendor documentation and through your own test sends before rolling out a signature widely.