As you know, when an account is deleted, the name of the user is set to their id, say user123.

Can we know the name(s) of this user when was an active account?

I did check data.SE but found nothing about this. Maybe through other sources?


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    $\begingroup$ Possibly you could infer something from comment replies on their posts (and to their comments) - although it is to some extent guesswork. There used to be a tool to list old usernames. The webpage no longer works, it seems that from Wayback Machine you can get the JavaScript code it used, see here and here. $\endgroup$ – Martin Sleziak Sep 30 '19 at 16:35
  • $\begingroup$ The same script is mentioned on Stack Apps: Find old display names of a user. However, I do not know enough about JavaScript to be able to say whether it can be modified in some way so that it works for deleted users. $\endgroup$ – Martin Sleziak Sep 30 '19 at 16:37
  • $\begingroup$ @MartinSleziak thank you. When I did click on Old display names of a user in your last link, shows "404 There isn't a GitHub Pages site here." doesn't even work for current active users. Thanks anyway. $\endgroup$ – Bellatrix Sep 30 '19 at 17:22
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    $\begingroup$ Yes, I have explicitly mentioned that the page no longer works. (Maybe I should have user the wording "no longer exists".) Still, you could be able to find the JavaScript that was used in the Wayback Machine - and try to use it yourself if you have enough time to tinker with it. $\endgroup$ – Martin Sleziak Sep 30 '19 at 17:35

One reasonable thing to do might be to check whether Google still remembers something about the given user and whether something can be found in the Wayback Machine. (I took one particular userid for testing - of course, the same can be done if we replace this by userid of another user.)

But possibly we can find something also from Data Explorer. (I have reworked my original attempt a bit.)

Using SEDE we can check comments/posts by a deleted user. If comments following them contain some comment reply ("@username"), it is quite likely that this might be the user in question. So at least some guess can be deduced from this.

Of course, you will get some reasonable results only for users who often engaged in discussions in comments.

I have no doubts that the queries can be improved in various ways by people who know more about SQL than I do.

One caveat to add is that some users tend to change their username relatively often. In such cases, the results could be rather inconclusive. You can check replies to comments and posts by one such users. (Possibly similar queries for existing users who tend to change their username might give you some guesses about their past usernames.)

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    $\begingroup$ Oh so the queries are in SQL. Is it like Java in difficulty? $\endgroup$ – Bellatrix Sep 30 '19 at 17:50
  • $\begingroup$ SQL is easier to learn compared to Java. It has fewer concepts and less syntax. $\endgroup$ – Ayman Hourieh Sep 30 '19 at 21:37

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