bookmarklet

A  bookmarklet  is a web browser bookmark that runs javascript commands on the current page; indieweb bookmarklets are often useful for responding to the current page.

IndieWeb Examples
Colin Morris uses a bookmarklet to find and reply to h-entry elements on the current page.

javascript:if (document.querySelector('.h-entry')) { window.open("https://vonexplaino.com/regenerate/reply.php?url=" + encodeURI(window.location.href));} else {child = document.createElement('p');child.style = "width:100%;text-align:center;position:absolute;z-index:4;top:0;color:red;background:white;font-size:xx-large";child.innerText = 'Nope';document.body.appendChild(child);}

IndieWeb-related bookmarklets
Instagram photo bookmarklet

Bookmarklets for WordPress
See WordPress Bookmarklets for Desktop

"Bookmarklets" on Android
Not technically a bookmarklet, the application Bookmarklet Free allows to integrate self-hosted publishing flows (e.g. a bookmarking tool or the like) into the default "Share" menu on Android; see Easy IndieWeb interactions on Android

It is also possible to set up a share target for Progressive Web Apps, enabling to "install" a personalised share target on Android (via mxb.dev)

MicroPub Clients
The Quill micropub client offers bookmarklets for bookmarking and favoriting as buttons within the footer of the app.

The Known CMS also offers a bookmarklet from within the "Tools and Apps" section of the settings page. It states: "The Known bookmarklet is the best way to save links, reply to posts, and share articles. Just drag the bookmarklet button below into your browser's Bookmark Bar."

microformats parsing
https://php.microformats.io/ has a bookmarklet to parse microformats on the current page, using the php-mf2 parser