Email Header Image Size (2026): Width, Retina, File Size for Mailchimp and Klaviyo

Email header image size, in short: make the header as wide as your email, usually 600 px (650–700 px in some builders), and export it at double width, 1200 px, so it stays sharp on high-resolution screens. Mailchimp's new builder is 660 px wide and suggests 1320 px images; Klaviyo suggests 600–1000 px. Keep each image at 1 MB or less, ideally much smaller.

More on this topic: Social media image sizes, every guide in one place.

The header is the first thing a subscriber sees when they open your newsletter, and for a product seller it's usually a hero shot of the new collection or the sale. Get the width wrong and it either breaks the layout, gets squeezed into a blurry strip, or takes so long to load that people scroll past it. Here are the widths the big email tools actually document, how tall to make a header, the retina rule, file sizes, and a layout that works in Gmail, Apple Mail and Outlook.

What size should an email header image be?

An email header image should be as wide as the email's content area, which is 600 pixels in most templates. Mailchimp's legacy templates are 600 px wide and its new builder is 660 px. Export the image at twice that width, 1200 or 1320 px, and it will look sharp on retina phones and laptops. Height is up to you; there's no standard.

Mailchimp's image recommendations, template width and image block help pages, and Klaviyo's email image best practices were checked in October 2026. Marketplaces change their rules, so confirm the current requirements in your seller dashboard before you upload a large batch.

The 600–700 px range is a long-standing convention, not a rule from any one company: it fits inside the reading pane of desktop email clients, and on phones the template scales the image down to the screen. If your platform isn't listed here, check its template settings for the content width and design to that.

What does Mailchimp recommend for header images?

Mailchimp recommends images of 660–1320 pixels wide in its new builder and 600–1200 pixels in the legacy builder. For the new builder it says to use images at least 660 px wide and to double that to at least 1320 px for retina displays. It recommends a maximum file size of 1 MB.

• Formats: PNG, JPG or GIF (the new builder's content studio also takes JPE, JPEG and BMP).
• Color: save images in RGB, not CMYK.
• Resolution: 72 DPI is generally enough for the web, but Mailchimp says it isn't required. Pixel width is what matters.
• Legacy templates are designed to be no wider than 600 px, and the width can't be changed in the campaign settings.

What does Klaviyo recommend for email images?

Klaviyo suggests keeping full-width images between 600 and 1000 pixels wide and under 2000 pixels tall, and recommends images of 1 MB or smaller; the hard limit is 10 MB. Images narrower than the full email can be smaller than 600 px. Klaviyo supports JPEG, PNG and GIF.

• Sharpness: Klaviyo's tip is to insert an image twice the size you need and reduce it in the template.
• Compression: Klaviyo compresses images automatically on upload (not GIFs) and marks a recommended version, which you can override if it looks blurry.
• PNG vs JPG: Klaviyo says PNG generally displays best, particularly for images with text.
• Warning: Klaviyo notes a full-width image at 72 DPI will often be larger than 1 MB, so resize and compress before uploading rather than relying on the editor.
• Alt text: Klaviyo says to always add it.

Why should an email header be twice the width?

Because most phones and many laptops have high-density (retina) screens with two or three device pixels for every CSS pixel. A 600 px image displayed at 600 px looks soft on them; a 1200 px image displayed at 600 px looks crisp. Mailchimp says this directly for its builder (1320 px for a 660 px email), and Klaviyo recommends the same 2× approach.

The trade-off is weight: double the width is roughly four times the pixels. That's why the next step, compressing, matters.

What file size should an email header image be?

Keep it at 1 MB or less, the maximum both Mailchimp and Klaviyo recommend, and in practice aim much lower. Neither publishes a smaller target, but a 1200 px photo header saved as a quality-80 JPG is usually a few hundred KB, which loads quickly even on a slow phone connection.

The targets in that table are common practice for fast-loading email, not a rule from Mailchimp or Klaviyo. The compress to 200 KB tool hits a specific size, and the image compressor lets you balance quality by eye. For a fuller explanation, see how to reduce image file size and JPG vs PNG vs WebP. Skip WebP for email; support across email clients is still patchy.

How tall should an email header be?

No email platform publishes a required height, so it depends on the job. A slim brand header with your logo is often 100–200 px tall at 1×; a hero image announcing a launch or sale is more often 300–400 px. Keep the headline and product visible in roughly the first 300–400 px of the email, the part most people see before scrolling.

These are common layouts, not platform specs. A product photo usually needs to become wider for a header: crop it with the free image cropper, pad it with the image resizer (custom size), or extend the scene so the product sits in a wide setting with room for a headline beside it.

How do I make an email header that works in every inbox?

Assume some subscribers won't see images at all, and design so the email still makes sense. Many email clients block or delay images until the reader allows them, and screen readers rely on alt text.

1. Put the offer in live text as well. “20% off this weekend” in HTML text below the header still shows when images are off.
2. Write alt text that says what the image says: “New autumn mugs, 20% off until Sunday”, not “header.jpg”. See product image alt text for examples.
3. Keep text in the image large. The header shrinks on a phone; anything under about 24 px at 1× becomes hard to read.
4. Avoid an all-image email. A single large image with no text is harder to read when images are blocked and is widely considered a spam signal.
5. Check dark mode. A logo with a transparent background can vanish on a dark inbox; a solid background or a light outline keeps it visible.
6. Send a test to Gmail, Apple Mail and Outlook accounts and look on a phone before the real send.

Email header checklist

1. Width matches the template (600 px, or 660 px in Mailchimp's new builder).
2. Exported at 2× (1200 or 1320 px) and displayed at column width.
3. JPG for photos, PNG for logos and text; RGB color.
4. 1 MB or less, ideally a few hundred KB.
5. Headline and product readable on a phone.
6. Alt text written; the offer repeated in live text.
7. Tested in dark mode and in Outlook.

Making email headers with AiArter

• Wide versions of product photos (8 credits per size). Extend a square shot into a 2:1 or 3:1 scene; the product stays exactly as photographed.
• Styled scenes for launch and seasonal headers, and design templates for sale banners.
• Free tools to crop, resize and compress the result without signing up.

AiArter doesn't send email; download the header and upload it to Mailchimp, Klaviyo or your email tool. For headers on your own site, see website image sizes and Shopify banner size.

Frequently asked questions

What size should an email header image be?

As wide as your email, usually 600 px (660 px in Mailchimp's new builder). Export it at 2×, 1200 or 1320 px, so it's sharp on retina screens. Height is your choice.

What size is a Mailchimp header image?

Mailchimp recommends 660–1320 px wide images in its new builder, at least 1320 px for retina, and 600–1200 px in the legacy builder. It suggests a 1 MB maximum file size.

What size images does Klaviyo recommend?

Klaviyo suggests 600–1000 px wide and under 2000 px tall for full-width images, 1 MB or smaller, with a 10 MB hard limit. It supports JPEG, PNG and GIF.

Should email images be 72 or 300 DPI?

DPI doesn't matter on screens; pixel width does. Mailchimp says 72 DPI is generally enough but not required. Export at 2× width instead of raising DPI.

What is the best file format for an email header?

JPG for photos, PNG for logos and images with text, GIF for simple animation. Avoid WebP, which isn't supported by every email client.

How tall should an email header be?

There's no official height. A logo bar is often 100–200 px tall and a hero image 300–400 px, measured at the 600 px display width.

Why does my email header look blurry?

Usually it was uploaded at 600 px and viewed on a retina screen, or compressed too hard. Upload a 1200 px version and compress it moderately.