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 though the frontend [3] and/or the API [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.
  • Andrew@piefed.socialEnglish
    1·
    5 months 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.

    • Kalcifer@sh.itjust.worksOP
      1·
      5 months ago

      […] 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. […]

      Eh, this is becoming rather pedantic, imo. I’m not sure what point you are trying to make.

    • Kalcifer@sh.itjust.worksOP
      1·
      5 months ago

      I saw your edit, yeah. […]

      Then what is it about me using your comment as a source makes you think that I viewed your response as “not good enough”?

    • Kalcifer@sh.itjust.worksOP
      1·
      5 months ago

      […] 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.

      This isn’t to discredit how you have internalized the exchange, so I apologize if I made you feel this way, but I want to assure you that it wasn’t my intent to single you out. I was simply looking for clarification because I felt that I might’ve found a potential ambiguity that I personally wasn’t sure of.