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Why do so many users have an identicon without a hash value (i.e. use the default identicon)?

I realized at some point that I kept seeing users with the same identicon. At first I brushed it off, but since I started noticing this, I've seen dozens of users with this same picture. I checked some of them out and concluded that they have to be different people, based on differences in their profiles, what sites each account is active on, and even the quality of their writing. There's also the matter of the sheer number of such accounts as there are almost three quarters of a million users with this avatar on Stack Overflow alone. (It is the most popular profile image.) The only thing that these users seem to have in common is that their accounts are pretty old and they all have this same image.

The image is this teal and white one:

Notably, the url for this is https://www.gravatar.com/avatar/?s=128&d=identicon&r=PG&f=1 (or similar, since some use a different size). Normal users have avatars like https://www.gravatar.com/avatar/123abbbbbbbbbbbbbbbbbbbbbbbbbbbc?s=128&d=identicon&r=PG (as an example). The obvious difference between these is that the second one has a MD5 hash (the 32 character hexadecimal string, which starts with 123 in my example) and the first one does not. This isn't answered by How is the default user avatar generated? because from that I would assume every profile should have a hash (no matter if the identicon was created before or after salting was started).

I'm just really curious now. Why did so many users get the identicon without a hash?


Examples:

Not an example, uses an Imgur uploaded version:

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  • 3
    Looks a bit like Null island ...
    – Glorfindel Mod
    Jun 5 at 18:14
  • PascalVKooten's profile picture is i.stack.imgur.com/hGOuLh.png, so I guess it's not a generated identicon (although it's the same image). All the others share the same (identicon) image source though. Jun 5 at 18:18
  • Does this answer your question? How is the default user avatar generated?
    – bad_coder
    Jun 5 at 18:41
  • 1
    @bad_coder Already mentioned in my question. I don't see anything there that explains why the hash would be missing entirely.
    – Laurel
    Jun 5 at 18:44
  • 1
    Only "a few" identical profile image urls: data.stackexchange.com/stackoverflow/query/1602299 ...
    – rene
    Jun 5 at 18:50
  • 1
    I expect something at Gravatars end where users can select "no identicon"? That at least would explain the urls without an uuid/hash
    – rene
    Jun 5 at 19:01
  • @Laurel What part about gravatar no longer being supported and the emoticon not being salted doesn't cover the question? It's generated by a function that gives no guarantees of avoiding collisions.
    – bad_coder
    Jun 5 at 19:04
  • 4
    @bad_coder the point is: there is no hash. Forget your bla bla about functions, salting and collisions. There is nothing ...
    – rene
    Jun 5 at 19:09
  • 1
    Does this answer your question? Unexpectedly changing identicon - if you choose Identicon, but don't have a Gravitar account; you only get the salted hash.
    – Rob
    Jun 5 at 19:14
  • @rene seems like "the default" gravatar identicon to me.
    – bad_coder
    Jun 5 at 19:18
  • 1
    Just another nail in Gravatar coffin, SE really really really must drop this and stop supporting it, it's bad, full of bugs, and I'm sure full with security holes as well. Should be simple enough to import all existing Gravatar images in use to imgur and just don't let user choose such option anymore. Jun 5 at 19:42
  • 1
    @Laurel ok, my issue then is: in your question (unless I'm mistaken) there are at least 2 users whose identicon leads to an URL without a hash, right? There's no magic there, behind an URL without a hash sits that 1 identicon (probably it's the default?!). Now, can you have another URL with a hash that gives the visually identical (I didn't check the images programmatically to ascertain if the similarity is only apparent or exact) image? Yes sure... Then, if the question is: how did it get to that? I do think the link dup targets more or less address the business process.
    – bad_coder
    Jun 5 at 20:06
  • 3
    I'm really not sure what you're asking here. The reason these users have the same identicon is because for all of them the identicon is being fetched without specifying a hash, so the default is used, for all of them. However, you've already identified that. So what are you really asking? Are you really asking "Why is no hash used for the identicon on a lot of users?" If so, then there's not going to be much more of an answer other than "when their current identicon was semi-permanently assigned, no value for the hash was used/available" (which will have multiple possible causes).
    – Makyen
    Jun 5 at 22:20
  • 2
    Hopefully the four of us (you, bad_coder, me, and Makyen) agreeing that the URL (that is 'blank' ) is what is used to create the Identicon satisfies this question. - The additional fields are blank, thus it's all seen as the same user; much as if the additional fields were filled in with identical information, and that would be thought to be the same user (even if it's not) - thus all creating the same image.
    – Rob
    Jun 5 at 23:36
  • 2
    I'm asking why the URL is blank, so saying that it's blank doesn't answer my question :l
    – Laurel
    Jun 6 at 16:08

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