Mailchimp Undefined Upload (7 Solutions)

Do you keep getting an undefined upload error whenever you try to upload an image to the Mailchimp newsletter editor? Super frustrating right?

You’re not alone in this struggle.

Many other users have also encountered this issue and there are a number of threads on the Mailchimp subreddit.

Fortunately, there are a few fixes and workarounds to get the images uploaded.

In this guide, I’ll go over some of the likely causes of the Mailchimp undefined upload error and show you how to upload your images to the editor.

What Causes The Mailchimp Undefined Upload Error?

This error usually means that Mailchimp was unable to process the image you attempted to upload and returned an “undefined” result.

⚡Also Read: Mailchimp campaign stuck on sending

I have a few theories why this would happen, but I am not 100% sure.

Nevertheless, let’s take a look at them before moving on to the workarounds.

Browser Issues

Some browser extensions, plug-ins, and add-ons can interfere with the image uploading process on Mailchimp – especially privacy or javascript disabling stuff.

Even the Mailchimp support staff commented on this on a community forum.

Browser cache and cookie problems (i.e corrupted) can be the reason behind this problem too.

Mailchimp might not also work smoothly on all web browsers and versions. In some cases, using an outdated / incompatible browser can trigger this error.

Problem On Mailchimp’s End

Sometimes this sort of error can occur due to some technical issue that has nothing to do with you but Mailchimp itself.

Bugs and other technical glitches are far more common on SAAS platforms than you think.

However, if this is the case, uploading should work again after a couple of hours. You can also check the mailchimp status page to see if there’s any known issues currently.

Other Causes

Apart from that, if the images you are trying to upload to Mailchimp are over the allowed 1MB file size, it might trigger this error.

Same goes for images in formats other than the supported JPG, JPEG, GIF, and PNG.

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Or maybe you might have not been connected to the internet when you tried to upload the image. Like you disconnected earlier and forgot to reconnect.

This has happened to me over a dozen times when I was uploading images to WordPress.

How To Fix The “Undefined Upload” Error On Mailchimp

Now, let’s dive into some fixes and workarounds you can try, so that you can get back to designing your newsletters:

Start With The Basics

Before you try anything else, quickly double check these to rule them out:

  • Make sure your image format is supported. Convert them if not.
  • If your image is larger than 1MB, compress it using a free online compressor.
  • Double check your internet connection. Also check the speed and stability.
  • Refresh the page. Close the tab and open a new tab and try it there.
  • Clear your browser’s cache and cookies.

That’s about it for the basic fixes.

Now’s the time for us to move on to some other solutions and workarounds for this problem.

Upload Image To The Library

Another workaround that some users have claimed to work is uploading images to the library first before opening the editor.

So instead of uploading your image to mailchimp’s email builder’s image placeholder, Go to My Files, and upload all the images you want.

The image should upload without any errors.

After that, get back to the email builder and select Insert image. Click Library here and select your image.

Upload Using A URL

Instead of uploading from your computer, try using the upload via URL feature. This is a good workaround that works almost all the time.

Here’s how to do it:

  1. Upload your image to an image hosting website like Imgur first.
  2. After it’s uploaded and shown to you, right click on the image and click “open image on new tab”
  3. This opens the direct image location. The URL should end with the image extension. Copy this URL to your clipboard.
  4. Get back to your Mailchimp editor, click Image and then click the drop-down menu next to Upload, and choose Import from a URL.
  5. Paste the URL we copied and click Import.
  6. This should upload the image. Select the image and click Insert.

Log Out And Back In

Some users have reported that logging out of their mailchimp accounts, and uploading the images after logging back in has worked for them.

Even though it’s not clear how it can work like that, just give it a try and see if it works for you too.

Disable Browser Extensions

Try disabling the extensions, add-ons, and plug-ins to see if it allows you to upload images to mailchimp as you normally would.

If you disable them one by one and try uploading an image after each, you might even be able to pinpoint the ones interfering with the image uploading and keep the rest functional.

Try A Different Browser Or A Computer

If you have other browsers installed, try logging in from one and uploading it. This solved the issues for some people – but didn’t for the majority.

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Mailchimp works fine with popular web browsers like Google Chrome, Mozilla Firefox, and Safari.

If you’re using an outdated or less common browser, switch to a supported one to see if that resolves the issue.

While you are at it, try logging in to your mailchimp account and uploading your images using a different computer. This worked for almost everyone.

Contact Mailchimp Support

If none of the solutions I have shown you work in fixing the Mailchimp undefined upload error, or if you think the issue originates from Mailchimp’s end, go ahead and contact Mailchimp support.

Explain the issue. They must already be familiar with it.

Quick Recap

The Mailchimp Undefined Upload error is common and only happens when you try to upload images using the editor. Most of the time, it’s either a bug or tech issue, or your browsers extensions are messing with the upload.

Even though there is no official solution, there are certain fixes and workarounds some users have reported that worked for them.

You can upload the images using URLs or upload them to the image library first. Other things like disabling browser extensions or using a different browser or computer will stop this from happening.

Give them a try and see if any of them works for you. If none of them do, contact mailchimp support and ask for their help.

About Author

Lito James is the founder of He is an entrepreneur and marketing specialist who helps businesses to get more leads, subscribers, and customers. Massive Peak has been featured on G2, Cloudways, Sujanpatel, GetResponse, Renderforest, and many more. Follow on LinkedIn | Twitter

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