Letting a reader pass a post on

The old way to do this was a row of buttons for Facebook, Twitter and Pinterest, each with one address to send somebody to. The fediverse has no such address: the destination is the READER's instance, and a page has no way to know it.

So the block is a list you write, and it holds three different kinds of thing:

share:
  - mastodon
  - bluesky
  - email
  - copy
  - system

Leave share: out and no block appears. The order here is the order they are drawn in.

bluesky, email, facebook, linkedin, threads and x are plain links: one address each, nothing to ask, no script. mastodon asks the reader once which instance they are on -- in a row that opens under the buttons, in the site's own type -- and remembers the answer in their browser. Not in a dialog from the browser: those look like something the page did not make, browsers throttle them, and a box demanding the name of a server is the shape people are taught not to trust. And no third-party redirector, which would put an outside service on every post page and in the way of every share. copy puts the address on the clipboard and says that it did. system hands it to the operating system's own share sheet, which on a phone is Signal and WhatsApp and Telegram and whatever else is installed, so one control covers what a row of them could not.

Three of them need the browser to co-operate, and none is drawn where it cannot work -- a control that opens nothing is worse than no control. mastodon stays hidden until its script has run, system unless the browser has a share sheet, and copy unless there is a clipboard to write to. That last one has a condition worth knowing about: browsers only give a page the clipboard over https, so on a site served over plain http:// the copy button is not drawn at all. If the whole block would be empty -- every target you named turned out to be one of these three, and none of them could run -- the block stays hidden too, rather than leaving a heading over nothing.

Pixelfed is not on the list. It has no share address to send anyone to -- the request for one was closed without it -- and a post there wants a photograph rather than a link.

What gets prefilled is the post's NAME and its address; the reader writes the part that is theirs. Nothing appears on a page, on a draft preview or on an unlisted post: there is nothing to pass on from a contact page, a draft has no address anybody else can open, and handing a reader a button that posts an unlisted post to Bluesky is the mistake the unlisted flag exists to prevent.