HTML in iCal attachment

Question

Can an iCal attachment contain HTML in the description property? If so, what are the restrictions?

Answer 1

After doing some research and testing. The answer is a qualified no. Meaning: you could throw it in there, but you shouldn't.

It is not strictly forbidden by the RFC, but DESCRIPTION is not the appropriate property for HTML content.

DESCRIPTION should be the plain text version of your content. The property X-ALT-DESC with a FMTTYPE declaration of text/html is the appropriate property for HTML content.

The following example worked in both Outlook and Gmail/Google Calendar, but does not appear to be supported by Thunderbird(w/Lightning): (please, forgive the ouput. it was generated by Outlook)

X-ALT-DESC;FMTTYPE=text/html:\n\n\n\n\n\n\n\n\n
Is this in HTML?
\n\n
Bullets:
\n\n
1. \; \; \; \; \;
     Test 1
\n\n
2. \; \; \; \; \; Test 2<
    SPAN LANG="en-us">
\n\n
\n\n\n

Like any HTML rendering in an email client supported tags and styles are limited.