PNG or JPG for Your Email Signature Images? Here’s How to Get It Right

What image format should you use for email signatures?

TL;DR

  • Use PNG when your image needs a transparent background. Logos on coloured or dark email backgrounds being the main example.
  • Use JPG for solid rectangular images like signature banners. JPG files are smaller and there is no quality benefit to using PNG here.
  • Keep total email size under 100KB where possible. Large images slow down loading and can affect deliverability.
  • Make your image at the correct display size before uploading. Uploading oversized images and scaling them down in HTML is one of the most common causes of unnecessarily large email signatures.

Why Email Signature Image Formats Matter

If you have ever looked at your agency’s email signature and noticed the logo sitting on an odd white box, or a banner that takes a moment to load, the chances are it comes down to image format or file size. Neither is complicated to fix, but getting it right makes a noticeable difference to how your emails look and how quickly they arrive.

Here is a plain-language guide to the format choices available, when to use each one, and how to keep your signature images lean.

PNG or JPG: The Practical Difference

Use PNG when you need a transparent background

PNG is the format to use when part of your image needs to be see-through. The most common example in email signatures is a logo.

If your agency logo sits on a transparent background in PNG format, it adapts to whatever is behind it, white, dark mode, a coloured email client theme. It looks correct everywhere. If you save that same logo as a JPG, the transparency is replaced with a solid colour (usually white), and on any background that is not white, your logo will have an obvious box around it.

So: if the image has a background that needs to disappear, use PNG.

Use JPG for solid rectangular images

For anything that is a solid rectangle (a signature banner, a promotional strip, a headshot on a coloured background) JPG is the better choice. JPG files compress well, which means they are significantly smaller than the equivalent PNG. There is no transparency to preserve, so there is no reason to pay the file size penalty that comes with PNG.

A banner image that is 80KB as a JPG might be 300KB or more as a PNG. Over an email that goes out to hundreds of candidates a day, that difference adds up.

FYI – JPEG and JPG are the same format. JPG is the modern convention.You say them the same, the both work, its annoying. JPG will be top of the list

What about other formats?

You may have come across WebP or SVG as modern, efficient image formats. They are both excellent for websites. For email signatures, they are best avoided.

Support across email clients is patchy. Outlook (which remains heavily used in corporate world and not going anywhere) does not reliably render either format. An image that displays correctly in Gmail may show as a broken placeholder in Outlook. Until support is consistent across the major clients, JPG and PNG remain the safe choices for email.

GIFs: fine, but with caveats

Some agencies use an animated GIF in their email signature. A subtle animation on a banner or a looping logo effect. There is nothing wrong with this, and GIFs are well-supported across most email clients.

The caveats are worth knowing. GIF files tend to be heavier than static images because they contain multiple frames. A small, well-optimised animated GIF is fine. A large one with complex animation will add meaningfully to your email size. If you are using a GIF, keep it simple, keep it short, and check the file size before it goes anywhere near a signature template.

Also worth checking: not all email signature management platforms handle animated GIFs correctly. Some flatten them to a static first frame. Test in your actual platform before rolling it out across the team.

Why File Size Matters for Email

Google has a threshold of around 102KB for Gmail. Emails above that size are clipped, with a “View entire message” prompt at the bottom. Most recipients never click it. If your email is being clipped, the bottom of your message (which often contains your signature) may not be seen at all.

Beyond Gmail’s clipping threshold, large images slow down load times, particularly on mobile. A candidate opening your email on a patchy connection may see a broken placeholder where your signature banner should be. First impressions in email are not just about copy.

From a deliverability standpoint, consistently large emails can also be a mild negative signal. It is not the primary factor in whether your emails reach the inbox, but it is one more unnecessary friction point.

Keeping your total email size under 100KB (including images) is a reasonable target. For most agency emails, this is achievable without compromising how the signature looks.

Keep File Sizes Small: The Practical Steps

Make the image at the correct size before you upload it

This is the single most effective thing you can do. If your signature banner displays at 600 pixels wide in most email clients, export it at 600 pixels wide. Uploading a 2,400-pixel-wide image and telling the email template to display it smaller does not reduce the file size. The full image still downloads, and then the email client scales it down. You are making the recipient’s device do unnecessary work.

If you are not certain what size you need, the safest approach is to prepare your images at a few different sizes (for a logo say, 40px, 60px, and 80px wide) and test how each looks in the email clients your recipients are most likely to use. Keep all of those versions in your image library or media folder so you have the right one to hand without going back to the designer. Label each logo with the file size to make life easier later!

Compress images before uploading

Even at the correct dimensions, images can often be compressed further without any visible difference. Tools like Squoosh (free, browser-based) or TinyPNG let you reduce file sizes meaningfully before the image goes anywhere near an email.

A JPG exported from design software at default settings is often larger than it needs to be. Running it through a compression tool first is a quick step that is worth making routine.

Keep your image library tidy

Whether your signature images live in your website’s media library or in a dedicated folder like the Cloudflare R2 subdomain setup we covered in a previous post, it helps to keep that library organised. Name files clearly, keep correctly-sized versions together, and remove old versions once they are no longer in use. A tidy library makes it faster to find the right file and less likely that someone grabs an outdated or oversized version by mistake.

What This Means for Recruiters

Email signatures go out constantly. Every email your consultants send to a candidate or client carries the signature, and across a team that is a significant volume of outbound communication. An oversized image or the wrong format is a small problem per email, but it is a persistent one and it is entirely avoidable.

The format and size decisions are usually made once, when the signature is first set up, and then forgotten. Getting them right at that point means you do not have to revisit them.

To summarise the decision:

  • Logo or image with transparency: PNG
  • Banner, strip, or rectangular graphic: JPG
  • Animated element: GIF, but check file size and platform support first
  • WebP or SVG: not yet, despite what your web developer might say

Frequently Asked Questions

What size should my email signature banner be?

600 pixels wide is a common standard for email, as it fits comfortably in most email clients on desktop. For file size, aim for under 30KB for a JPG banner and under 50KB for a PNG logo. These are not hard rules, but they are a reasonable target.

Can I use SVG for my logo in an email signature?

SVG is excellent for websites but not reliable in email. Outlook does not support it, and support varies across other clients. Use a PNG with a transparent background for logos instead.

Why does my logo have a white box around it in some emails?

This almost always means the logo was saved as a JPG rather than a PNG. JPG does not support transparency, so the transparent areas of the original image are filled with white. Re-export the logo as a PNG with a transparent background.

What is the Gmail clipping threshold?

Gmail clips emails that exceed approximately 102KB in total size, showing a “View entire message” prompt. Signature images are a common contributor to emails hitting this threshold. Keeping images compressed and correctly sized is the main way to stay below it.

Do I need different image sizes for mobile and desktop?

Most email clients scale images responsively, but it is worth testing on mobile. If your banner looks oversized on a phone screen, reducing its display width in the signature template (rather than uploading a different file) is usually the simplest fix.

Need Help?

If you want help reviewing your agency’s email signature setup ( formats, file sizes, hosting, or the authentication records that sit behind your sending domain) book a call at quinset.co.uk/bookings.