Web Viewer displays local HTML as plain text (not rendered) when using Post Message or asset URL

Questions about Thunkable Issues / Bugs
1

Hi everyone,
I’m building an app that uses a local html file to reformat and display an API responses in a styled way. The goal is for the HTML file to act as a render layer with the API text sent into it via the Web_Viewer → Post Message block.

Here’s what I’m seeing:

  • The html file loads in the Web Viewer (it shows up).

  • However, instead of rendering HTML, the Web Viewer shows the raw HTML source as plain text.

  • Even when I send messages via the Post Message block, the content updates, but still as literal HTML text (no rendering).

  • The file contains the proper <html> structure and the thunkableWebviewerExtension.js import for message handling (in case that was needed).

  • I’m testing this in both Thunkable Live on iOS and Web Preview, same result.

It seems like the Web Viewer isn’t actually evaluating the local HTML file — it’s just printing it.

Has anyone successfully:

  • Sent HTML content to a local Web Viewer asset and had it render, not print as text?

  • Used Post Message to inject dynamic HTML into a local file that uses the Thunkable WebViewer extension?

Expected: HTML renders normally (e.g., styled text, line breaks)
Actual: HTML shows as escaped text (e.g., <div>content</div> instead of formatted output)

Has anyone found a reliable workaround (maybe a data:text/html URL or hosted HTML page) to make the Web Viewer actually execute the HTML?