- The upload caps and recommended sizes at a glance
- No headroom between the cap and the recommendation
- Getting a large photo under 1MB
- Widths for multi-column layouts
- Formats that work and formats that don't
- Importing by URL and keeping files private
- My advice for images that never get rejected
- Frequently asked questions
Mailchimp's content studio accepts images up to 1MB each and other file types up to 10MB each. Mailchimp also recommends keeping images at 1MB or less, saved as PNG, JPG or GIF, and between 660 and 1320 pixels wide in the new email builder, or 600 to 1200 in the legacy builder.
The upload caps and recommended sizes at a glance
Phone cameras produce big files, and a single product shot can easily be several times larger than an email needs. Here's everything Mailchimp documents about image size, format and width in one place.
| Item | Limit | Applies to |
|---|---|---|
| Image upload limit | 1MB each | Content studio uploads |
| Other file types | 10MB each | Content studio uploads |
| Recommended image file size | 1MB maximum | Images in emails and landing pages |
| Recommended image width, new builder | 660 to 1320 px | Email, template width 660px |
| Recommended image width, legacy builder | 600 to 1200 px | Email, template width 600px |
| Supported image types | JPG, JPE, JPEG, GIF, PNG, BMP | Content studio |
No headroom between the cap and the recommendation
Mailchimp Help's Use the content studio page sets the upload limit for images at 1MB, and the template image guidance recommends a maximum of 1MB too. The two numbers are the same, so there's no margin at all. A 1.5MB photo won't go in untouched: it has to be compressed or resized first. Documents and other file types get more room, at 10MB each.
The same page notes that Mailchimp renames every uploaded file to a unique ID number, and you can't change it afterwards. If you rely on file names to keep track of versions, keep your own naming in the folder on your computer, not in the studio.
Getting a large photo under 1MB
The good news is that an email image rarely needs to be anywhere near 1MB once it's sized for the template. The width numbers are your best friend here.
- Check which builder you're using. New builder templates are 660px wide; legacy templates are 600px wide.
- Resize the image to fit. In the new builder use 660 to 1320 pixels wide, in the legacy builder 600 to 1200.
- Save it as JPG for photos, PNG when you need transparency, or GIF for simple animation.
- Make sure it's saved in RGB, not CMYK.
- Check the file is 1MB or less, then upload it to the content studio.
Resizing a huge photo down to 1320 pixels wide usually does most of the work on its own. If it's still over, export it again at a slightly lower quality setting. For animated files, my roundup of tools that shrink GIF files can help, and if you need to trim a photo to shape first, there's my list of simple image croppers.
Widths for multi-column layouts
If you're placing images side by side, each one needs less width. Mailchimp's recommended minimum widths in the new builder are:
- 660px for a full-width section
- 330px for a 2 column section
- 220px for a 3 column section
- 165px for a 4 column section
Smaller images mean smaller files, so a 4 column layout is very unlikely to bump into the 1MB cap. It's the single hero image at the top of an email that usually causes trouble.
Formats that work and formats that don't
The content studio supports JPG, JPE, JPEG, GIF, PNG and BMP files. Within that list, Mailchimp's own recommendation for emails is PNG, JPG or GIF, with PNG when you need to keep transparency, such as a logo on a coloured background.
Colour mode matters too. Images should be saved in RGB, because CMYK doesn't render accurately online and can break an embedded image. If your designer works in print, ask for RGB exports for anything going into an email.
PDF, PSD and AI files can't be used as campaign images at all, because those types aren't consistently supported across browsers. Export a JPG or PNG from the design file instead. If you want to share the PDF itself, it falls under the other file types limit of 10MB.
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Importing by URL and keeping files private
You don't always have to upload. The content studio lets you import an image from a URL instead, which can save a step if the image already lives on your website.
One thing to keep in mind: all files uploaded to the public gallery are public. Don't put anything sensitive in an image or document you upload, such as a customer list in a screenshot or an internal report.
My advice for images that never get rejected
Size every image to the template width before you upload it, not after. For the new builder that means 1320 pixels wide for a crisp full-width image, saved as an RGB JPG, which almost always lands well under 1MB. If you're weighing whether another email platform would suit you better, my comparison of MailerLite and Mailchimp is a useful starting point.
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Frequently asked questions
What is the Mailchimp image file size limit?
You can upload images up to 1MB each and other file types up to 10MB each to the content studio.
Which image formats does Mailchimp accept?
The content studio supports JPG, JPE, JPEG, GIF, PNG and BMP. Mailchimp recommends PNG, JPG or GIF for emails.
What image width should I use in Mailchimp emails?
660 to 1320 pixels in the new builder, and 600 to 1200 pixels in the legacy builder.
Why was my file renamed?
Mailchimp changes the file name to a unique ID number on upload, and it can't be changed.
Can I use a PDF as an image?
No. PDF, PSD and AI files can't be used as campaign images.
