I remember a specific account's old alias, but can't find any trace of it on here. Not sure if they've changed their name or just deleted their account. Is there a way I can look up an account by its old alias?

if they've been quoted/mentioned in the forums, blips, or comments, potentially yes. you could try just searching their old username on those; if they're still using the same ID and haven't swapped to a new account that should lead to their current username.

darryus said:
if they've been quoted/mentioned in the forums, blips, or comments, potentially yes. you could try just searching their old username on those; if they're still using the same ID and haven't swapped to a new account that should lead to their current username.

I 100% know their old alias but I can't seem to find any forum posts, comments, or blips mentioning them. Unfortunately I have no idea what their ID was.

The system stopped carrying old nicknames because of stalking issues. While some users were fine with others knowing their previous aliases, others were not.

furrin_gok said:
The system stopped carrying old nicknames because of stalking issues. While some users were fine with others knowing their previous aliases, others were not.

Makes sense. Thanks.

furrin_gok said:
The system stopped carrying old nicknames because of stalking issues. While some users were fine with others knowing their previous aliases, others were not.

More-or-less this. If you have previous name(s), they're listed on your profile page. It used to be that this was visible to everyone, but now it's only visible for yourself.

All user name changes, including old names, are still publicly visible in the mod actions log (despite not being a mod action). The search interface doesn't work for non-admins, but you could scroll down the list and see if there's anyone you think you recognise after the date you last saw them.

There is a similar list for user deletions, although it doesn't include the old name.

chloober said:
I 100% know their old alias but I can't seem to find any forum posts, comments, or blips mentioning them. Unfortunately I have no idea what their ID was.

Try googling "username" site:e621.net but replace username with the old alias you remember. Keep the quotations.
This will bring up any mentions of them on old comments or forum posts, and you can link it with the account who posted that comment.