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Assets & Images

MailJawn includes an asset library for managing images used in your email campaigns. Upload once, use across any project in your organization.

Uploading Images

  1. Go to Dashboard → Assets
  2. Click Upload Image
  3. Select an image from your device
  4. Optionally add a description
  5. Click Upload

MailJawn processes the image before storing it:

  • Supported formats: JPEG, PNG, GIF, and WebP
  • WebP images are converted to JPEG automatically for email client compatibility
  • Images wider than 1,200px are resized to 1,200px width (maintaining aspect ratio)
  • JPEG images are compressed at 85% quality with optimization enabled

You'll see warnings if any processing was applied (resizing, conversion, compression) — these are informational, not errors.

Tip

For the best results, upload images that are already 1,200px wide or smaller. This avoids resizing and keeps you in control of the final quality.

Size Recommendations

Keep individual images under 500 KB after processing. Larger images work but may slow down email loading on mobile devices. MailJawn will warn you if an image exceeds this threshold.

Images with extreme aspect ratios (taller than 3:1) also trigger a warning. Very tall images can look awkward in email layouts — consider a more horizontal crop.

Browsing the Library

The asset library shows your images in a grid (6 per row, 24 per page). You can:

  • Search by filename to find specific images
  • Sort by upload date (newest first by default)
  • View details for any image — dimensions, file size, format, and upload date

Using Assets in Campaigns

When composing an email in MJML, reference an asset by its URL. Each asset has a public URL that you can copy from the asset detail view.

<mj-image src="https://your-cdn.example.com/org-id/images/hero-banner-a1b2c3d4.jpg" />

Assets are served with a 1-year cache header, so they load quickly for subscribers who've seen them before.

Organization-Wide Sharing

Assets belong to your organization, not to individual projects. This means:

  • An image uploaded from Project A is available in Project B
  • You don't need to upload the same logo or banner multiple times
  • All team members in the organization can use any asset

The asset library tracks which project originally uploaded each image for reference, but access is not restricted.

Editing and Deleting

Editing

After upload, you can update an asset's description. The image itself (filename, dimensions, format, URL) cannot be changed — upload a new version instead.

Deleting

Deleting an asset removes it from the library and deletes the file from storage. This is a soft delete — the record is kept for audit purposes but the image is no longer accessible.

Warning

If you delete an asset that's referenced in an email draft, the image link will break in future sends. Already-sent emails are not affected — the image was delivered inline or cached by email clients.

Supported Formats Reference

Format Supported Notes
JPEG Yes Best for photos; compressed at 85% quality
PNG Yes Best for screenshots, logos, and images with transparency
GIF Yes Supports animation; use sparingly in emails
WebP Upload only Automatically converted to JPEG (most email clients don't support WebP)