Unexplained failure of compiler. "The compiler output error was"

I have an app which is working fine in the companion but the compiler fails for no reason.

I have also deleted and reinstalled the latest BLE extension.

Error message screen shot attached

My app: BassMixer.aia (1.1 MB)

thanks for your help,


I removed this folder in your assets folder

I don't know what kind of image you uploaded there. This should work now.

BassMixer.aia (1.1 MB)

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You might read

Using Images with App Inventor


Images and Sounds

Most instances of Developers getting that error response is due to issues with the Project's images (usually large images) that the app cannot handle. A rule is, make your images 'right sized.' Do not rely on the ability of the compiler to 'make images fit' ... that uses lots of processing power and can cause your app to fail.

Here are some resources to help you learn to use the AI2 tools. A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook http://www.appinventor.org/book2 ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.

There is a free programming course here http://www.appinventor.org/content/CourseInABox/Intro and the aia files for the projects in the book are here: http://www.appinventor.org/bookFiles

How to do a lot of basic things with App Inventor are described here: http://www.appinventor.org/content/howDoYou/eventHandling .

Also look here http://kio4.com/appinventor/index.htm and here http://www.imagnity.com/tutorial-index/ for more tutorials.

Learn about components http://ai2.appinventor.mit.edu/reference/components/

and visit the Library http://appinventor.mit.edu/explore/library


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The cause is undoubtedly the Base 64 png image. This format cannot stand alone, it should be contained e.g. in an HTML file.

Store this in a text file, then return it with a file component. Or just store it as an image, most likely this will take up less space than a base64 text of the image.

You can't have folders in assets.


Cool, thanks heaps for the help.

Cool, thanks heaps for all the tips and guide links.

much appreciated.

Hi MuzzaBass

Very Important question, please help us - did you put that file in your Project Media or did it just appear all by itself. We have another AI User with a similar issue.

Hi Chris,

No, I didnt put the file in project, didnt even realise it was there. I only added the 2 other pics which are working fine.

Hope this helps,


That's massive, thanks Murray. Keep a look out for files finding their way into your media tray.

Hi Murray

Sorry to bother you again, MIT is trying to get to bottom of this issue and would appreciate more info:
Your OS and OS version
Your Browser and Browser Version
... trying to see if there is a common denominator amongst those affected.