Protocol handler?

[rimu@piefed.social]

I'm going to register a protocol handler, so links to anywhere on the fedi will be opened in the user's home instance.

https://developer.mozilla.org/en-US/docs/Web/API/Navigator/registerProtocolHandler

Has anyone already done this and if so what was the prefix you used? We might as well all use the same thing. I'm thinking web+fedi.

[mimic_kry@sh.itjust.works]

Too soo-...wait what fucking year is it

Woopsie. Sorry, posted in the wrong place. I'll leave my dumbassness up

[julian@community.nodebb.org]

rimu@piefed.social interesting idea... I know Evan has some thoughts about this as part of his ActivityPub HTML discovery project

https://swicg.github.io/activitypub-html-discovery/

I am not sure why they did not settle on protocol handlers but I've tagged him for comment

evan@activitypub.space evan@cosocial.ca

[julian@community.nodebb.org]

The concept sounds excellent, although there is fairly limited mobile support.

Since NodeBB is an installable PWA it would be definitely nice to have it supported there as well.

[tchambers@indieweb.social]

@julian I write about this here: near zero mobile browser support but strong desktop browser support- and I suggest a JavaScript fallback for the others …. https://www.timothychambers.net/2025/06/24/the-seven-deadly-fediverse-ux.html

[evan@cosocial.ca]

@rimu web+acct

[die4ever@retrolemmy.com]

It's a good idea, but web+fedi or web+activitypub is maybe too broad to be useful? I wouldn't want a Lemmy post to open in Mastodon, and pretty sure opening a Mastodon post in Lemmy is impossible unless the post was directed to a community.

web+threadiverse could solve that issue but that's kinda hacky. Too bad (AFAIK) they can't be stacked like web+fedi+threadiverse with some kind of priority system.

There was a discussion about this for Lemmy but it was never implemented https://github.com/LemmyNet/lemmy-ui/issues/3031

Maybe the real solution is to improve Lemmy and Mastodon so that they are capable of doing these things decently.

I was actually thinking of making a browser extension that handles this instead. Each Fediverse software could write something to window.fediverse or something like that, with tags for threadiverse, group support, micro blogging, etc. The extension could have methods to infer these values for existing platforms. But the extension could give a dialog box to redirect, based on your preferred instances for certain tags.

[die4ever@retrolemmy.com]

What does acct stand for?

[evan@cosocial.ca]

@Die4Ever

https://datatracker.ietf.org/doc/html/rfc7565

[silverpill@mitra.social]

@rimu

web+ap, which was proposed by Fedilink authors. To my knowledge, it is the most widely adopted proposal

https://web.archive.org/web/20250402041648/https://fedilinks.org/

(the main site seems to be offline now)

cc @SoniEx2

[julian@community.nodebb.org]

Are there implementors of web+ap? I'd be interested in adopting.

I assume the fallback behaviour is to just assume https?

[silverpill@mitra.social]

@julian Fedilinks website lists 3 MastoAPI clients, but the list is incomplete. I saw Fedilinks being mentioned in changelogs of other clients too.

There was also an Akkoma PR, it was closed by the author: https://akkoma.dev/AkkomaGang/akkoma/pulls/589. I don't quite understand the reasoning, perhaps @smitten could clarify.

[julian@community.nodebb.org]

The PR comments suggest that making the various changes to the backend were too large to justify, and a front-end only approach would be preferred? smitten@key.portend.place

It raises a good point though, where if you serve web+ap://, it's not understood by clients that are not aware of this scheme. If there were a way a client could communicate whether there is a protocol handler registered, then the server could tailor its response.

[smitten_@key.portend.place]

Glad to see more people having this idea! The problems we ran into were in helping the browser understand the address and know where to forward. Each server implements lookup routes differently, so there's not necessarily a generic path that you can trust is available on https on the person's home server, even if you know their home server origin. So in some ways the feature should be offered by your home server software, maybe offering a website that does the handler registration to its known lookup/redirect address.

But that is limiting in a few ways. It's a lot of extra steps for each person to do (browsers' default UI for registering protocols is not obvious or easy). It doesn't carry over to different devices, and if you have more than one home server in some way, you are back dealing with that not-great browser UI to pick which handler you want.

In general people are more accustomed to registering protocols to apps they have installed, especially phone apps. It's much easier to register them there and you don't have to have approval flow UI, but taking that approach moves this whole served handler route out of the backend again, so we have to start thinking more along the lines of web+ap-compatible servers that handler clients know how to call or bounce to.

@julian@community.nodebb.org @silverpill@mitra.social @SoniEx2@chaos.social @rimu@piefed.social

[smitten_@key.portend.place]

Also I want to highlight this excellent comment by Yumechi about fingerprinting and de-anonymization risks.

https://socialhub.activitypub.rocks/t/fep-07d7-a-custom-url-scheme-and-web-based-protocol-handlers-for-linking-to-activitypub-resources/3588/53

@SoniEx2@chaos.social @silverpill@mitra.social @julian@community.nodebb.org @rimu@piefed.social

[silverpill@mitra.social]

@smitten_ Do you know what is the status of Fedilinks? Has it been abandoned?
FEP-07d7 was withdrawn, and other proposals have even less support than these two.

@SoniEx2 @julian @rimu @activitypub

[evan@activitypub.space]

rimu@piefed.social I've been using web+acct for the acct URI format.

https://en.wikipedia.org/wiki/Acct_URI_scheme