Embedding of Media/Sites: Known issues with 3rd party solutions

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Embedding from external websites (based on tests done before):

Google Drive (PDF/Docs/Spreadsheet): Need to use the URL in embed code instead of the shareable URL
Google Form: Supported
Box.com: Need to use the URL in embed code instead of the shareable URL
Dropbox: Embedding is not allowed
OneDrive: Need to use the URL in embed code instead of the shareable URL
Youku: Need to use the URL in embed code instead of the shareable URL
YouTube: Supported
Instagram: Not supported directly (workaround needed to create a HTML file to implement embed codes)
Direct Link to file (i.e. URL ends with file extension): Dependent on device/browser support, so it's safer to say not supported

If anybody needs a quick reference from what I have tested before: