> This page is part of the [Customer.io documentation](https://docs.customer.io). For the complete index, see [llms.txt](https://docs.customer.io/llms.txt).
> Last updated: September 1, 2026
> To take actions in Customer.io from an agent, use the [Customer.io CLI](https://docs.customer.io/ai/cli/get-started.md) or the [MCP server](https://docs.customer.io/ai/mcp/get-started.md).

# Assets library: store files

Your workspace has an Assets library where you can store images and PDFs for reuse across messages (email, in-app, etc.).

## How it works

Any images you upload are stored in your [Assets](https://fly.customer.io/workspaces/last/journeys/assets) page.

*   You can upload images in `bmp`, `jpeg`, `png`, and `gif` formats.
*   You can store PDFs that you then link to from a message.

 ![The list view of the asset page. A folder of social icons, logos, then individual files.](https://docs.customer.io/images/asset-library-2.png)

### File size limits

You can upload images and PDFs to your Assets library, but limits apply:

*   Maximum image width and height: 4096 px
*   Files must be smaller than 2 MB.
*   For optimal loading times, we recommend that you upload images smaller than 1 MB.

You can upload and optimize images larger than 2 MB

You can optimize images larger than 2 MB when you upload them through [Design Studio](/messaging/design-studio/emails/visual-editor/overview/#upload--optimize-images) or the [Assets page](#optimize-images).

## Add files

To add a file to Assets, you can go to [*Content > Assets*](https://fly.customer.io/workspaces/last/journeys/assets) or upload an image while creating a message.

From *Assets*, click **Upload Assets** to get started.

### Insert an image

Learn more about adding images through our editors:

*   Email
    *   [Design Studio](/messaging/design-studio/emails/visual-editor/overview/#upload--optimize-images)
    *   [Drag-and-drop](/messaging/channels/email/editors/drag-and-drop/#add-images)
    *   Rich text: Click in the toolbar.
    *   Code: Click in the toolbar.
*   In-app: Click an image-based [component](/messaging/channels/in-app/editor/components/#components-at-a-glance) and choose your file.
*   [Push](#copy-link-for-message)
*   [SMS/MMS](#copy-link-for-message)
*   [Slack](/messaging/channels/image-support/#images-in-slack)

### Link to an image (push and SMS)

For push notifications and SMS/MMS, you’ll need to upload your images to *Assets* first then copy the link and paste it into your message.

1.  Go to *Content > Assets*, and find the image you want to copy.
2.  Hover over the image, and click .

    ![Click the link icon to copy an image URL](https://docs.customer.io/images/asset-hover-state.png)

3.  Go to your message and paste the URL where you need to use your image.

Learn more about adding links to [push](/messaging/channels/push/send-push/#create-a-push-notification) and [SMS](/messaging/channels/sms/send-messages/#add-smsmms-messages-to-your-workflow).

### Link to a PDF

If you want to include a PDF for your customers, you’ll upload it to *Assets* first, and copy the link. Then you’ll hyperlink text in your message to the PDF. The way you link to a PDF depends on the type of editor you use.

Learn more about [email attachments and transactional messages](/messaging/channels/email/attachments/#try-sending-a-link-rather-than-an-attachment).

#### Design Studio

In **Design Studio**, you can link to PDFs in text-based components.

1.  Go to *Assets*, and click to copy the PDF link.
2.  Go to your email, highlight some text, and click from the bubble menu.
3.  Leave “URL” as the type, and paste in your PDF link.

#### Drag-and-drop email editor

In the **drag-and-drop editor**, you can link to PDFs in text blocks. Click , change the *Link Type* to “File Manager,” and select your PDF.

 ![Link to a PDF](https://docs.customer.io/images/email-link-to-pdf-2.png)

#### Code email editor

In the **code editor**, click **Insert**, and select your PDF to insert a link to the file. We automatically hyperlink the word “PDF”, so remember to change that text to something that suits your message.

#### Rich text email editor

1.  Click **Insert**, and click to copy the link to your PDF.
2.  Highlight the text, click , and paste the link you copied.

## Optimize images

You can optimize images directly from the Assets page to reduce file size. This is useful for images that are already in your library.

1.  Go to [*Create content > Assets*](https://fly.customer.io/workspaces/last/assets) and find the image you want to optimize.
2.  Hover over the image and click .
3.  Adjust the settings:
    *   Use **View type** to compare the original image against the optimized version.
    *   Use **Compression type** to balance file size vs. visual fidelity.
    *   Use **Retina mode** to manage pixel density for high-resolution screens.
4.  Click **Save optimized image**.

The optimized image does not replace the original in your Assets library; it creates a new version.

## Organize your files

You can organize your images and PDFs into folders and move your files around through drag-and-drop.

1.  From *Assets*, click **New Folder**, and enter the name of your new folder.
2.  Then move your files:

*   Click and hold to drag files into the folder or
*   Hover over files, check the boxes, then click and hold to drag them into folders.

### Sort and filter assets

By default, the Assets page sorts images by creation date in descending order; the most recent images are at the top. You can change the sort value and order to find your files.

*   Use the dropdown to change the sort value between Created, Name, or Size.
*   Select or to change the sort order.
*   Click to display your images in a list and to show large thumbnails.

## Delete assets

Hover over a file, and click to delete it.

To delete multiple items, hover over files, check the boxes, and then click **Delete**.

**Deleting a file in use does not impact messages**; you must remove or replace the file within a message editor to change the image.

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