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Preview a local Universal Editor extension

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Learn how to .

To preview a Universal Editor extension during development, you need to:

  1. Run the extension locally.
  2. Accept the self-signed certificate.
  3. Open a page in Universal Editor.
  4. Update the location URL to load the local extension.

Run the extension locally

This assumes you have already created a and want to preview it while testing and developing locally.

Start your Universal Editor extension with:

$ aio app run

You’ll see output like:

To view your local application:
  -> https://localhost:9080
To view your deployed application in the Experience Cloud shell:
  -> https://experience.adobe.com/?devMode=true#/custom-apps/?localDevUrl=https://localhost:9080

This runs your extension at https://localhost:9080 by default.

Accept the self-signed certificate

Universal Editor requires HTTPS to load extensions. Since local development uses a self-signed certificate, your browser must explicitly trust it.

Open a new browser tab and navigate to the local extension URL output by the aio app run command:

https://localhost:9080

Your browser will show a certificate warning. Accept the certificate to proceed.

Accept the self-signed certificate

Once accepted, you’ll see the local extension’s placeholder page:

Extension is accessible

Open a page in Universal Editor

Open Universal Editor via the or by editing a page in AEM Sites that uses Universal Editor:

Open a page in Universal Editor

Load the extension

In Universal Editor, locate the Location field at the top center of the interface. Expand it and update the URL in the Location field, not the browser address bar.

Append the following query parameters:

  • devMode=true – Enables development mode for Universal Editor.
  • ext=https://localhost:9080 – Loads your locally running extension.

Example:

https://author-pXXX-eXXX.adobeaemcloud.com/content/aem-ue-wknd/index.html?devMode=true&ext=https://localhost:9080

Update the Universal Editor location URL

Preview the extension

Perform a hard reload of the browser to ensure the updated URL is used.

Universal Editor will now load your local extension—only in your browser session.

Any code changes you make locally will be reflected immediately.

Local extension loaded

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