Support mailto: links in navigation

[Jehong-Ahn]

What version of starlight are you using?

0.39.3

What is your idea?

Support mailto: links in navigation by treating them as absolute URLs. This would allow email links to be used directly in nav items.

Why is this feature necessary?

mailto: is a standard URI scheme and is commonly used for contact links. Currently it is treated as a relative path because isAbsoluteUrl() only recognizes http:// and https://. Supporting mailto: would make navigation more flexible with minimal impact.

Do you have examples of this feature in other projects?

Mintlify supports mailto: in navigation item href values.

Participation

• I am willing to submit a pull request for this feature.

[delucis]

Thanks for the report @Jehong-Ahn!

I think we may be able to update the isAbsoluteUrl() check to recognise other protocols like mailto: for now if you'd like to try a PR?

Ultimately we should probably move to not process link entries at all given we now have the slug ones that can provide all that kind of automated formatting. But that's more of a disruptive change so I'd start by just fixing mailto: specifically.

[Jehong-Ahn]

I took another look at the code, and I'm not sure adding mailto: directly to isAbsoluteUrl() is the right approach. The function is also used for favicon handling, and its name implies an actual absolute URL check.

Adding a mailto: special case there feels a bit awkward, so I'll leave this one with you for now. Thanks for taking a look @delucis !

[delucis]

I opened #4092 which will add support for this, so going to close this. Thanks again for bringing our attention to it @Jehong-Ahn!