Type a handle and see every list it was added to, and who added it. Signed in as that account, you can add any of those curators to a list of your own, one at a time. Nothing is added unless you press the button.
Who listed you comes from
constellation.microcosm.blue's
backlink index of app.bsky.graph.listitem records (it starts 2025-01-28; older untouched adds may be missing).
Each record is read through slingshot.microcosm.blue and each list is named by the public AppView. Adding back creates an
app.bsky.graph.listitem record in a list you already own, straight from your browser to your PDS — nothing else is requested or stored.
Suggestion: if a list is plainly garbage, "add back" is for the lists that earned it. Be a little kind about it.
built by @buildthis.bisks.net, asked for by @jessehattabaugh.com, from an idea by @asura.dev