Email Image Sizes for Newsletters and Campaigns

I spent three weeks building a product launch email last year. Beautiful photography, carefully written copy, a color palette our designer had agonized over. It looked absolutely stunning in our email builder’s preview pane. Then I sent the test email to myself, opened it in Outlook desktop, and watched my gorgeous hero image render as a tiny blue question mark icon floating in a sea of white space.

That little blue question mark haunts me. Because here’s the thing — I’m supposed to know better. I’ve been sending marketing emails for years. And I still got bitten by the most predictable problem in email: images that look perfect in your design tool and completely fall apart in someone’s inbox.

If you’ve ever had that sinking feeling — the one where you hit send to 50,000 subscribers and then realize your images might be broken for half of them — this guide is for you. I’m going to walk through the exact image sizes, file formats, and dimensions that actually work across every major email client. No guessing. No “it depends.” Just the numbers that won’t let you down.

Why Email Is the Worst Place for Images

I don’t say this lightly: email is the single worst medium for displaying images on the internet. Worse than ancient browsers. Worse than feature phones. It’s a landscape so fragmented and backwards that it makes cross-browser CSS debugging feel like a vacation.

Here’s why. Web browsers update automatically every few weeks. Email rendering engines? Some of them haven’t been meaningfully updated since 2007. Outlook desktop still uses Microsoft Word’s rendering engine to display HTML emails. Let that sink in. Your marketing email is being rendered by a word processor. A word processor that doesn’t understand half of modern CSS, doesn’t support background images properly, and has opinions about image sizing that can charitably be described as “creative.”

And it gets worse. Many email clients block images by default. Gmail used to do this. Outlook still does for external senders. Yahoo has its own set of quirks. Apple Mail is actually the most capable email renderer out there, which is great until you remember that it only accounts for a portion of your subscriber base.

Then there’s the WebP situation. On the web, WebP has been the gold standard for image optimization for years — smaller files, better quality, universal browser support. In email? Gmail only started supporting WebP in 2023, Outlook desktop still doesn’t support it reliably, and several smaller email clients choke on it entirely. So that carefully optimized WebP image you’d use on your website? It might show up as a broken image in your subscriber’s inbox.

The takeaway isn’t that you should give up on email images. It’s that you need to be deliberate about every single decision — dimensions, file size, format, alt text — in a way that the modern web doesn’t require anymore. For a comprehensive look at how bulk resizing fits into your broader image workflow, check out our bulk image resizing guide.

The Email Width Problem Nobody Talks About

Here’s a number that surprises most marketers the first time they hear it: 600 pixels. That’s the maximum safe content width for email, and it has been since roughly 2005. Twenty-plus years of smartphone revolutions, retina displays, and responsive design, and email templates are still built around a constraint from the flip phone era.

Why 600 pixels? Because Outlook’s preview pane — the sidebar that shows email content without opening the full message — is roughly 600 pixels wide. Go wider than that, and your email either gets clipped or triggers a horizontal scrollbar that nobody will ever use. Your subscriber will see the left side of your image and assume the email is broken.

But here’s the part that really trips people up: 600 pixels is the maximum. Your actual image display area is usually narrower. Most email templates use padding — 20 to 30 pixels on each side. A two-column layout splits that 600 pixels in half, minus the gutter between columns. By the time you account for padding, gutters, and the structural table cells that hold email layouts together, your hero image might only have 560 pixels of actual display space. A product image in a two-column grid? Maybe 260 to 280 pixels.

I’ve seen marketers export their hero images at 1200 pixels wide because their designer worked in a 1200-pixel canvas. The email client dutifully downloads all 1200 pixels of image data, then squishes it into a 560-pixel container. The subscriber just downloaded twice the data they needed, the email loaded slower, and the image might actually look slightly softer because of the downscaling. Nobody wins.

The fix is straightforward: resize your images to match the actual display width before you add them to your email. Not the canvas width. Not the “it looks about right” width. The exact pixel width of the content area where the image will appear.

What Every Email Client Actually Supports

Not all email clients are created equal, and pretending they are is how you end up with broken images for a chunk of your audience. Here’s what you’re actually dealing with:

Email Client	Max Width	JPG	PNG	GIF (Animated)	WebP	Image Blocking
Gmail (Web)	600-640px	Yes	Yes	Yes	Yes	Off by default
Gmail (Mobile)	Device width	Yes	Yes	Yes	Yes	Off by default
Outlook Desktop (2019+)	~600px	Yes	Yes	Partial*	No	On for external
Outlook Web (365)	~600px	Yes	Yes	Yes	Yes	Off by default
Outlook Mobile	Device width	Yes	Yes	Yes	Yes	Off by default
Apple Mail (macOS)	Flexible	Yes	Yes	Yes	Yes	Off by default
Apple Mail (iOS)	Device width	Yes	Yes	Yes	Yes	Off by default
Yahoo Mail	~600px	Yes	Yes	Yes	Partial	Off by default
Thunderbird	Flexible	Yes	Yes	Yes	Yes	On by default

*Outlook desktop renders animated GIFs as a static first frame. Your fancy animated product showcase? It’s a still image for a big slice of your audience.

A few things jump out from this table. First, JPG and PNG are the only truly universal formats. Every single email client handles them without issues. Second, WebP support is getting better but isn’t universal enough to rely on as your only format. Third, Outlook desktop is the problem child — it blocks images by default for external senders, doesn’t support WebP, and mangles animated GIFs.

The practical advice? Stick with JPG for photographs and most marketing imagery. Use PNG when you need transparency (we’ll talk about dark mode later). Save GIFs for simple animations, and always design your animated GIFs knowing that some recipients will only see the first frame. And avoid WebP in email entirely until Outlook desktop catches up, even though it’s the best format for web images.

The Sizes That Actually Work

Alright, let’s get to the specific dimensions. I’ve tested these across every major email client, and they’re the sizes that consistently render correctly without clipping, stretching, or triggering weird scaling behavior. (If you need dimensions beyond email — social media, e-commerce, print — our image dimensions reference has every platform covered.)

Hero Images

Your hero image is the centerpiece of your email. It’s the first visual element most subscribers see, and it sets the tone for everything below.

Recommended size: 600 x 300 pixels (2:1 ratio)

This is the sweet spot. A 600-pixel-wide hero fills the full content width of a standard email template. The 2:1 aspect ratio gives you enough vertical space for impact without pushing your call-to-action below the fold on mobile. Some marketers go taller — 600 x 400 or even 600 x 600 — but I’d argue against it. On a phone screen, a 600 x 600 hero image takes up nearly the entire viewport, and your subscriber has to scroll before they see any text or CTA. That’s not engagement; that’s a speed bump.

If you’re running a wider template (640 pixels), adjust your hero to 640 x 320. The ratio matters more than the exact pixel count.

Product Images

For single-product features in a full-width layout, go with 600 x 600 pixels. The square format works cleanly across devices and gives the product enough visual presence.

For product grids — which are bread and butter for e-commerce emails — each product image should be 260 x 260 to 300 x 300 pixels depending on your column layout. Two-column grids work best with images around 280 pixels wide. Three-column grids push you down to 180 to 190 pixels per image, which is tight but workable for products that don’t need a lot of detail.

Thumbnail Images

Blog roundups, article previews, or content digests typically use smaller images alongside text. 100 x 100 to 150 x 150 pixels works well for these. Any smaller and the image loses its purpose. Any larger and it starts competing with the text for attention.

Banner and Promotional Images

Full-width promotional banners follow the same rules as hero images: 600 pixels wide, with height depending on your content. Skinny announcement bars (600 x 80 or 600 x 100) work well for sale announcements and event reminders. Standard promotional banners at 600 x 200 give you room for a headline, a visual, and a CTA button all within the image.

A word of caution: putting text inside images is risky in email. If images are blocked — and they will be for some recipients — your entire message disappears. Always include important information as live text in addition to any text-in-image elements.

File Size: The Silent Deliverability Killer

Most email marketers obsess over subject lines and send times. Almost nobody talks about image file size, which is weird, because it might be the single most impactful technical factor in whether your email actually reaches the inbox.

Here’s what happens when your images are too big. First, your total email weight increases. Most email clients have a size threshold beyond which they clip the email — Gmail, for example, clips emails larger than 102 KB of HTML. That’s just the HTML; images are loaded separately. But the total download weight still matters for mobile users on cellular connections. An email with four product images at 500 KB each means your subscriber’s phone is downloading 2 MB of image data before they can even see your products. On a spotty 4G connection, that’s several seconds of staring at empty alt-text rectangles.

Second — and this is the one that keeps email deliverability specialists up at night — oversized images can trigger spam filters. Email security systems track the text-to-image ratio and the total email weight. An email that’s mostly large images with minimal text looks suspiciously like spam. I’ve seen legitimate marketing emails land in the spam folder purely because the images were too heavy, pushing the total email size past what the spam filter considered reasonable.

Target file sizes for email images:

• Hero images: 40-80 KB
• Product images: 20-60 KB
• Thumbnails: 5-15 KB
• Promotional banners: 30-70 KB
• Total email image weight: Under 800 KB (ideally under 500 KB)

Getting your images down to these sizes usually requires a combination of resizing and compression. Resize to the exact display dimensions first — there’s zero reason to send a 2000-pixel-wide image that’ll display at 600 pixels. Then compress the resized image at 70-80% JPEG quality. You’d be amazed at how much file size that one-two punch removes. A 1.5 MB product photo becomes a 45 KB email-ready image, and your subscribers can’t tell the difference.

For a deeper dive into compression techniques, our guide on batch compressing images covers the workflow in detail.

Retina Displays Changed the Game (But Not the Way You Think)

Here’s where things get interesting. Everything I’ve said so far is about pixel dimensions — the actual number of pixels in your image file. But modern phones and laptops have retina displays that pack two (or three) physical pixels into every CSS pixel. An image that’s 600 pixels wide looks sharp on a standard display but slightly soft on a retina screen, because the screen is stretching 600 pixels of data across 1200 physical pixels.

The fix is a technique called 2x images: you create your image at double the display dimensions, then set its width in HTML to half its actual pixel size. So a hero image would be 1200 x 600 pixels in the file, but displayed at 600 x 300 pixels in the email. The retina screen uses all 1200 pixels, so the image looks crisp.

Should you do this? Honestly, it depends.

The pro argument: retina images look noticeably sharper, especially for product photography where detail matters. If you’re selling watches, jewelry, or anything where customers zoom in mentally while looking at your email, the extra clarity is worth it.

The con argument: 2x images are roughly four times the file size (twice the width times twice the height equals four times the pixels). That 45 KB hero image at 600 x 300 becomes a 120-180 KB hero image at 1200 x 600. Multiply that across six images in your email and you’ve just tripled your total email weight. On mobile networks — which is where retina displays live — those extra kilobytes mean extra loading time.

My recommendation? Use 2x images for your hero and primary product images, and skip it for thumbnails, decorative elements, and secondary images. The hero image is where first impressions are made, so invest the file size there. The rest can be standard resolution without anyone noticing.

When you’re preparing retina images, BulkImagePro’s resizer makes this painless. Resize your source images to 1200 pixels wide (2x your 600-pixel display width), compress them at 60-70% quality (you can be more aggressive because the downscaling hides compression artifacts), and export as JPG. The compressed 2x image often ends up only slightly larger than an uncompressed 1x image. If you’re worried about quality degradation during the resize step, our guide to resizing without quality loss covers the techniques that keep retina images sharp.

Batch Resizing Email Images the Fast Way

If you’re sending a weekly newsletter, you’re resizing email images every week. Product launches, seasonal campaigns, event invitations — they all need images sized to the same email-friendly dimensions. And if you’re also pushing those campaigns to social channels, you’ll need a separate set of dimensions entirely — our social media image sizes guide covers every platform. Doing this one image at a time in Photoshop or Preview is a recipe for wasted afternoons.

Here’s the workflow I use with BulkImagePro that takes about two minutes regardless of how many images I’m processing:

Step 1. Open BulkImagePro’s bulk resizer in your browser. No download, no account, nothing to install.

Step 2. Drag in all your campaign images at once. Product photos, hero images, headshots for team announcements — everything. BulkImagePro handles up to 50 images per batch.

Step 3. Set your target width to 600 pixels for full-width images (or 300 for two-column product grids, or 1200 if you’re going the retina route). The tool maintains aspect ratios automatically, so your images won’t get stretched or squished.

Step 4. Download everything as a ZIP file. All images resized, all consistently dimensioned, all ready to drop into your email builder.

If your images also need compression — and they almost certainly do — run them through BulkImagePro’s compressor immediately after resizing. Or if you need to crop them to a specific aspect ratio first (say, square crops for a product grid), do that before resizing.

The whole pipeline — crop, resize, compress — takes less time than manually resizing three images in Photoshop. And because every image gets identical settings, your email looks consistent instead of having one product photo that’s noticeably sharper or larger than the others.

For broader context on how resizing fits into your overall image workflow, our complete guide to image compression covers the full optimization pipeline from capture to delivery.

Dark Mode and Email Images: The Gotcha Nobody Warns You About

Dark mode in email is one of those features that sounds simple and is actually a nightmare. When a subscriber turns on dark mode in their email client, the client inverts the color scheme — white backgrounds become dark, dark text becomes light. Straightforward for text. Absolutely chaotic for images.

Here’s what actually happens. Some email clients (Apple Mail, Outlook desktop) leave images completely alone in dark mode. Your image looks exactly the same on a dark background as it did on a light one. Other clients (Gmail app on Android, some versions of Outlook mobile) apply a semi-transparent dark overlay to images, which can make bright images look washed out and muddy. And some clients (Outlook.com in dark mode) invert the colors of images entirely, turning your brand’s blue logo into an eerie orange.

The biggest casualty is logos and icons on transparent backgrounds. If your logo is a dark wordmark on a transparent PNG, it’ll be invisible on a dark background. The subscriber sees nothing. They might see a faint rectangular outline where your logo should be, or they might just see blank space.

How to protect your images in dark mode:

For logos: Don’t use transparent PNGs. Instead, give your logo a solid background — white, your brand color, whatever works. Or add a thin padding of solid color around the logo so it’s always visible regardless of the background. Yes, it’s slightly less elegant than a floating transparent logo. But elegance doesn’t matter if nobody can see it.

For product images: Shoot products on white backgrounds, and make sure the white extends all the way to the edges of the image. When dark mode inverts the email background, your product image becomes a white-bordered rectangle on a dark background — which actually looks fine. The product stands out. Compare that to a product on a transparent background, which would float on the dark background with no visual separation.

For illustrations and graphics: Use colors that have enough contrast against both light and dark backgrounds. Avoid very light grays, pale yellows, and other colors that disappear on white and get washed out in dark mode. When in doubt, test by putting your image on a dark gray background and squinting.

For PNG-to-JPG conversion: If you’re currently using transparent PNGs in your emails and dark mode is causing problems, the simplest fix is to convert those PNGs to JPGs with a white (or colored) background. You lose transparency, but you gain predictability. And in email, predictability is worth more than elegance.

The bottom line: design your email images assuming they might appear on any background color. That single mental shift prevents 90% of dark mode problems before they happen.

Putting It All Together: Your Email Image Checklist

Before you hit send on your next campaign, run through this quick sanity check:

Dimensions — Every image is sized to its actual display width. Hero images at 600px wide (or 1200px for retina). Product images at 260-300px for grid layouts. No image wider than your template’s content area.

File size — Each image is under 80 KB. Total image weight is under 800 KB for the entire email. If you’re over, run the images through BulkImagePro’s compressor before uploading.

Format — JPG for photographs and complex images. PNG only when you need transparency (and you’ve tested it in dark mode). No WebP. Animated GIFs only where the message works as a still image too.

Alt text — Every image has descriptive alt text. Not “image1.jpg.” Not “photo.” Actual descriptions that make sense when the image is blocked.

Dark mode — No logos on transparent backgrounds. Product images have solid backgrounds that extend to the edges. Graphics use colors with adequate contrast on both light and dark backgrounds.

Retina — Hero image and primary product images are 2x resolution. Secondary and decorative images are standard resolution to keep total file size manageable.

Nail these six things and your email images will render correctly for the vast majority of your subscribers, regardless of what email client they’re using.

Frequently Asked Questions

What's the ideal image width for email newsletters?

600 pixels is the standard maximum content width for email newsletters. Most email clients, including Outlook's preview pane, render content at or below this width. After accounting for padding in your template, your actual image display area is typically 560-580 pixels. For retina displays, you can create images at 1200 pixels wide and set the display width to 600 pixels in your HTML for sharper rendering on high-density screens.

Can I use WebP images in marketing emails?

Not reliably. While Gmail and Apple Mail support WebP, Outlook desktop does not render WebP images, and several smaller email clients have inconsistent support. Stick with JPG for photographs and PNG for images requiring transparency. WebP is excellent for websites, but email client support hasn't caught up yet. Use BulkImagePro's converter to switch formats if needed.

How do I resize multiple email images at once?

Use a bulk resizing tool like BulkImagePro's resizer to process up to 50 images simultaneously. Drag all your campaign images in, set your target width (600px for full-width, 300px for two-column layouts), and download everything as a ZIP. The tool maintains aspect ratios automatically so images won't be distorted. All processing happens locally in your browser with no file uploads.

What file size should email images be?

Individual email images should be under 80 KB each, with total image weight per email staying under 800 KB (ideally under 500 KB). Hero images typically land between 40-80 KB, product images between 20-60 KB, and thumbnails between 5-15 KB. Oversized images slow loading on mobile, can trigger spam filters, and hurt deliverability. Resize images to their exact display dimensions first, then compress them at 70-80% JPEG quality.

Do I need retina (2x) images in email?

It depends on the image. For hero images and primary product photography where detail matters, 2x retina images (1200px wide displayed at 600px) provide noticeably sharper rendering on modern phone and laptop screens. For thumbnails, decorative elements, and secondary images, standard resolution is fine -- the visual difference is minimal and you'll save significant file size. When using 2x images, compress more aggressively (60-70% quality) since downscaling hides compression artifacts.

How do I fix email images that break in dark mode?

The most common dark mode issue is logos on transparent PNG backgrounds becoming invisible against dark backgrounds. Fix this by giving logos a solid background color or a thin border of padding. For product images, ensure white backgrounds extend to the image edges so they form a clean bordered rectangle in dark mode. Avoid transparent PNGs for critical visual elements, and test your email in dark mode before sending. Converting PNGs to JPGs with a white background eliminates most dark mode rendering problems.

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Ready to resize your email images in bulk? Try BulkImagePro’s free resizer — batch resize up to 50 images at once to the perfect email dimensions, with no signup and no uploads. Need to compress them too? Run them through our free compressor to hit those email-friendly file size targets.