Solution

The Lemmy server appears to have a database limit of 255 characters [2]; however, individual instances appear to put their own limits on username length [3][4.1][4.2].

Original Post

If you know, please also provide relevant documentation.

UPDATE (2025-02-02T06:06Z): I did some brute-force testing, and, at least for sh.itjust.works, it seems that the maximum username length is 50, and the maximum password length is 60 [1].

References
  1. “Sign Up”. sh.itjust.works. Lemmy. Accessed: 2025-02-02T08:49Z. https://sh.itjust.works/signup.
    • When creating an account on sh.itjust.works, the sign-up form will throw this error if the provided password is greater than 60 characters in length.
  2. @TootSweet@lemmy.world To: [“[SOLVED] What is the maximum username length for a Lemmy account?”. “Kalcifer” @Kalcifer@sh.itjust.works. “Lemmy Support” !lemmy_support@lemmy.ml. sh.itjust.works. Lemmy. Published: 2025-02-03T00:54:51Z. https://sh.itjust.works/post/32085936.]. Published: 2025-02-02T05:57:26Z. Accessed: 2025-02-03T00:44Z. https://sh.itjust.works/post/32085936/16442382.

    It might be 255 characters? […]

    • They pointed to code on GitHub for the Lemmy server which outlines the length of the username data in the SQL database.
  3. “[SOLVED] What is the maximum username length for a Lemmy account?”. “Kalcifer” @Kalcifer@sh.itjust.works. “Lemmy Support” !lemmy_support@lemmy.ml. sh.itjust.works. Lemmy. Published: 2025-02-03T00:54:51Z. Accessed: 2025-02-03T00:46Z. https://sh.itjust.works/post/32085936.
    • §“Original Post”. ¶2.

      […] I did some brute-force testing, and, at least for sh.itjust.works, it seems that the maximum username length is 50 […]

      • The maximum username length for sh.itjust.works was found to be 50 characters by brute-force testing the length limit.
  4. “Andrew” @andrew_s@piefed.social To [“[SOLVED] What is the maximum username length for a Lemmy account?”. “Kalcifer” @Kalcifer@sh.itjust.works. “Lemmy Support” !lemmy_support@lemmy.ml. sh.itjust.works. Lemmy. Published: 2025-02-03T00:54:51Z. https://sh.itjust.works/post/32085936.] Published: 2025-02-02T19:57:49Z. Accessed: 2025-02-03T00:59Z. https://sh.itjust.works/post/32085936/16453656.

    1. curl -L http://lemmy.world/api/v3/site | jq -r .site_view.local_site.actor_name_max_length (26)

      • The maximum username length for Lemmy.world was found to be 26 characters via an API request.

    2. curl -L http://sh.itjust.works/api/v3/site | jq -r .site_view.local_site.actor_name_max_length (50)

      • The maximum username length for sh.itjust.works was found to be 50 characters via an API request.
  • Kalcifer@sh.itjust.worksOP
    1·
    18 days ago

    […] I give you reproducible command-line instructions, which match up with your own findings, and it’s apparently not good enough. […]

    Did you perhaps not see that I cited your comment’s findings as a source for the solution…? Or is it that you can’t believe that I would dare to exhibit any amount of skepticism of your claim?

    • Andrew@piefed.socialEnglish
      1·
      18 days ago

      I saw your edit, yeah. I’m not some precious person who thinks no-one should dare question their claims. To my mind, though, what I said wasn’t a claim. A claim would be if I’d said “lemmy.world is 26, sh.itjustworks is 50” with no further info. Instead, I gave command-line instructions for you to run yourself, so you could get the answers for those instances (and any other instances) from Lemmy’s backend itself. If I wasn’t reasonably sure that the backend was giving you the numbers you were looking for, I wouldn’t have mentioned it.

      I wasn’t reacting to being questioned, though, I was reacting to being singled-out for being questioned. You marked this as “Solved” based - also - on a test from you, and an answer from TootSweet, but it didn’t look like to me that you ever questioned whether those answers deserved a follow-up. Neither of those, in my opinion, are really good enough, but I’ll say why in the answers to your individual comments about them.