You can, but maybe you shouldn't. Given that this post is in the fediverse community, I don't feel too bad about mentioning that Lemmy is part of a federated network with PieFed and MBIN (I try not to bollock on too much about the platform I happen to be using).

In the ActivityPub JSON for this post, there is no indication that this field contains MarkDown. If anything, it says the opposite, it says it contains HTML. It's therefore not unreasonable for other platforms to render it as such.

Given this, and the poor support for mobile clients indicated in the comments, and the fact that it's only a subset of MarkDown tags, but include ones that aren't part of CommonMark standard, I'd argue that it's not necessarily a good idea.

[–] flamingos@feddit.uk 13 points 3 weeks ago (1 children)

In the ActivityPub JSON for this post, there is no indication that this field contains MarkDown. If anything, it says the opposite, it says it contains HTML. It’s therefore not unreasonable for other platforms to render it as such.

Actually, the name property is explicitly plain text, it shouldn't contain any type of markup, whether that be markdown or HTML.

[–] andrew_s@piefed.social 3 points 3 weeks ago (1 children)

Oh, wow. Thanks.

For clarity, I wasn't intending to say that PieFed treats that field as HTML (it treats it as text), I just meant that if you were looking at that JSON, and being a bit lazy like me and not looking at specs, then it wouldn't be unreasonable to assume that the 'mediaType' field also refers to 'name' (rather than a 'content' field which this post doesn't happen to have).

Anyway, this seems to be even more reason why MD shouldn't be put in titles, and front-ends shouldn't be encouraging the practise by rendering it.

[–] kat@orbi.camp 2 points 3 weeks ago

Eh, I'll probably use italics tho, just like I did * in reddit.

[–] AA5B@lemmy.world 2 points 3 weeks ago (1 children)

In the ActivityPub JSON for this post, there is no indication that this field contains MarkDown. …. it says it contains HTML

This seems like a bug. Regardless of what clients may support, the json ought to accurately describe fields

[–] andrew_s@piefed.social 5 points 3 weeks ago

Another commenter (who's contributed code to Lemmy) pointed to a link that provides the specification for that field: "A simple, human-readable, plain-text name for the object. HTML markup MUST NOT be included."

So in this case, it's more that the JSON looks a bit ambiguous: 'mediaType' is only referring to the format of the text in a post's body, but - unlike me - you'd also need to be aware of the spec to know that it doesn't apply to the title.

[–] schnurrito@discuss.tchncs.de 1 points 3 weeks ago (2 children)

Do you know a way to see the ActivityPub JSON for fediverse objects?

[–] andrew_s@piefed.social 5 points 3 weeks ago (1 children)

Yes - it's easy to do from a command line. For this post, it would be:

curl --header 'accept: application/activity+json' --location https://lemmy.world/post/24241974 | jq .

it looks like

{  
  "@context": [  
    "https://join-lemmy.org/context.json",  
    "https://www.w3.org/ns/activitystreams"  
  ],  
  "type": "Page",  
  "id": "https://lemmy.world/post/24241974",  
  "attributedTo": "https://lemmy.world/u/amon",  
  "to": [  
    "https://lemmy.world/c/fediverse",  
    "https://www.w3.org/ns/activitystreams#Public"  
  ],  
  "name": "By the way, you can have `Markdown` in Lemmy post titles",  
  "cc": [],  
  "mediaType": "text/html",  
  "attachment": [],  
  "commentsEnabled": true,  
  "sensitive": false,  
  "published": "2025-01-13T20:48:50.824942Z",  
  "language": {  
    "identifier": "en",  
    "name": "English"  
  },  
  "audience": "https://lemmy.world/c/fediverse"  
}

[–] schnurrito@discuss.tchncs.de 1 points 3 weeks ago

Thanks, will try that out

[–] BentiGorlich@gehirneimer.de 5 points 3 weeks ago

you can use https://browser.pub/ I like it very much for that use case :)

[–] vk6flab@lemmy.radio 16 points 3 weeks ago (6 children)

Word of caution, it doesn't render on Connect for Lemmy.

[–] amon@lemmy.world 7 points 3 weeks ago (1 children)

Hmm, but the best part about markdown is that it is human readable regardless so it should still be fine

[–] rickyrigatoni@lemm.ee 4 points 3 weeks ago

i am not human

[–] catloaf@lemm.ee 6 points 3 weeks ago* (last edited 3 weeks ago)

Nor Boost. It does in Raccoon, though.

[–] steventhedev@lemmy.world 5 points 3 weeks ago (1 children)

or in Jerboa

[–] borth@sh.itjust.works 13 points 3 weeks ago (2 children)

Works in Voyager!

[–] AceSLS@ani.social 2 points 3 weeks ago

Not for me

[–] homesweethomeMrL@lemmy.world 1 points 3 weeks ago

Boom.

[–] kat@orbi.camp 1 points 3 weeks ago

Renders fine in Sync

[–] IronKrill@lemmy.ca 1 points 3 weeks ago

Or Thunder

[–] lemmyng@lemmy.ca 1 points 3 weeks ago

Renders in Summit, but I turned that off because any post title starting with # is rendered as h1.

[–] driving_crooner@lemmy.eco.br 14 points 3 weeks ago (2 children)

If you have markdown on your title, then is not being rendered by Jerboa.

[–] f4f4f4f4f4f4f4f4@sopuli.xyz 3 points 3 weeks ago

Do you also have the Android weirdness in which the tick marks appear to be in a different place? (Not Jerboa-specific)

[–] kat@orbi.camp 1 points 3 weeks ago

Sync for lemmy works

[–] bdonvr@thelemmy.club 9 points 3 weeks ago

You can also edit them after the fact unlike other platforms

[–] JohnnyEnzyme@lemm.ee 7 points 3 weeks ago (1 children)

(unlike Reddit, for example)

I use bold and italic a lot in post titles. Some of the other stuff wouldn't make much sense I don't think, but every little bit helps.

[–] amon@lemmy.world 8 points 3 weeks ago* (last edited 3 weeks ago) (2 children)

I mean, code could work and maybe ^superscript^ or ~subscript~ and that's about it I think

[–] infeeeee@lemm.ee 6 points 3 weeks ago (2 children)

Can you create headings in headings?

[–] smeg@feddit.uk 5 points 3 weeks ago (1 children)

You can, and it'll probably get annoying if everyone catches on!

[–] infeeeee@lemm.ee 6 points 3 weeks ago (1 children)

OK, I will never use it again.

[–] smeg@feddit.uk 2 points 3 weeks ago

~oh no~

[–] smeg@feddit.uk 2 points 3 weeks ago (1 children)

Are sub and superscript officially supported by markdown now? Or is that a Lemmy-specific extension?

[–] infeeeee@lemm.ee 3 points 3 weeks ago

Lemmy-ui uses markdown-it: https://github.com/LemmyNet/lemmy-ui/blob/main/package.json#L65

Markdown-it follows the CommonMark spec with extensions: https://spec.commonmark.org/current/ As I see superscript is not part of the spec, but listed in the markdown-it readme as a plugin, so I guess it's coming from there: https://github.com/markdown-it/markdown-it?tab=readme-ov-file#syntax-extensions

They are also listed in package.json:

    "markdown-it-sub": "^2.0.0",
    "markdown-it-sup": "^2.0.0",

https://github.com/LemmyNet/lemmy-ui/blob/main/package.json#L73

Lemmy docs about markdown support: https://join-lemmy.org/docs/users/02-media.html#text

[–] misk@sopuli.xyz 7 points 3 weeks ago (1 children)

What good is it for if I can’t change post title font to Comic Sans.

[–] motor_spirit@lemmy.world 4 points 3 weeks ago (1 children)

ABSOLUTELY NOTHIN

[–] rickyrigatoni@lemm.ee 3 points 3 weeks ago

Good god, ya'll.

[–] Fitik@fedia.io 6 points 3 weeks ago

@amon@lemmy.world Doesn't render it on Mbin

[–] AmidFuror@fedia.io 6 points 3 weeks ago

I'd settle for good spelling and grammar. Once most posters have mastered that, let them play with the formatting.

[–] perviouslyiner@lemmy.world 3 points 3 weeks ago

Be careful of the character limit on each viewer, as they can "trim" your title in the middle of some markup tag and just display part of it as the title.