Insane start at any of the recognized protocols are the ones shown at: Section "Known URL protocols".
  • http://
  • https://
absolutely anywhere if not escaped, e.g.:
renders something like:
a <a href="">
To prevent expansion, you have to escape the protocol with a backslash \\, e.g.:
Empty domains like:
don't becomes links however. But this one does:
Insane links end when either the end of the document or one of the following characters is found:
  • space
  • newline \n
  • open or close square bracket [ or ]
  • open or close curly braces { or }
As a consequence, to have an insane link followed immediately by a punctuation like a period you should use an empty argument as in:
Check out this website:[].
which renders as:
Check out this website:
otherwise the punctuation will go in it. Another common use case is:
As mentioned on the tutorial ([see this link]).
which renders as:
As mentioned on the tutorial (see this link).
If you want your link to include one of the terminating characters, e.g. ], all characters can be escaped with a backslash, e.g.:
Hello\]a\}b\\c\ d world.
which renders as:
Note that the inside \a[] only works because we do some post-processing magic that prevents its expansion, otherwise the link would expand twice:

which renders as:
This magic can be observed with --help-macros by seeing that the href argument of the a macro has the property:
"elide_link_only": true,