Jellyfin server v12.0 RC2 release

[theguymadmax]

We are pleased to announce the second release candidate preview release of Jellyfin 12.0!

This is a preview release, intended for those interested in testing 12.0 before it's final public release. We welcome testers to help find as many bugs as we can before the final release.

As always, please ensure you stop your Jellyfin server and take a full backup before upgrading!

## A note about versioning

Starting with this release, we are **dropping the preceeding 10. from our versioning**. Thus, 10.11.x -> [10.]12.x = 12.x. The reason is simple: at this point in the project, we don't envision a hard break in the API like we planned way back in the early days, and this version scheme was causing a lot of confusion amongst users about what a "major" release was. For more information, please see [the RC1 release notes](https://github.com/jellyfin/jellyfin/rel.../v12.0-rc1).

Note: If you install the RC, you should **disable all plugins** and reinstall using [the unstable plugin repository](https://jellyfin.org/docs/general/server...positories), or plugins may fail to load and cause unintended side effects.

## What's new?

The main goal of this release has been performance. 10.11.0 dropped a **major** backend rewrite, and while it was broadly functional, it had a lot of rough edges. This release seeks to polish out most of those rough edges and bring better performance to all users.

For the full changelog, please see the GitHub releases:
https://github.com/jellyfin/jellyfin/rel.../v12.0-rc2
https://github.com/jellyfin/jellyfin-web.../v12.0-rc2

[Graeme]

It's surprisingly quiet in here, isn't it? Figured I'd post how my test went.

TL;DR: The upgrade was smooth and it works fine.

Well done to the whole Jellyfin team on this! I'm impressed and excited at the pace of development and the way this is going. I know the big database changes in 10.11 were traumatic for everyone, but these version 12 RCs show that it will be worth it in the long run and things are definitely looking up from here.

My setup is that my media is on a NAS and my Jellyfin server is on a separate Ubuntu 24.04 VM on one of my Proxmox hosts, installed using the repo at https://repo.jellyfin.org/ubuntu according to the docs. The server accesses the media using read-only NFS mounts. It is available to a VERY limited number of users via my public-facing web server on a separate VM, which runs Apache on Rocky Linux, with a virtual host configured as a reverse proxy. My library contains around 1020 movies, 380 TV series and 22,300 episodes.

I cloned my production Jellyfin server VM, changing things like the MAC address of the NIC, the machine-id and hostname and ensured it was correctly mounting the library NFS shares as read-only. I ensured it was fully updated and used apt to install the downloaded .deb files for 12.0-rc2.

The first startup took several minutes while showing the new, prettier migration progress on the web interface. Once complete the new web interface displayed with no issues at all and seemed quite responsive. (Although, it should be noted I wasn't previously experiencing significant performance issues on 10.11.11 either as some others have reported.) I completed a full media scan of all libraries, which took several minutes. Unfortunately I didn't record the actual time for the full scan, but it didn't seen excessive to me. Quite a few minutes, but well less than an hour.

So far I'm only accessing locally over http, but it appears to be working just fine.

[Graeme]

Now my test server has been running for a couple of days, I notice that some of my Scheduled Tasks may not be running. For example the "Scan Media Library" task shows "Last ran 2 days ago..." even though I have looked to confirm it is set to run every 12 hours.

Is this a known issue or something peculiar to what I've done?
What troubleshooting should I do?

[HokieRulz]

I just upgraded my jellyfin server dev instance (debian 13 lxc on proxmox) from 10.11.11 to 12rc2.  The upgrade was easy and in very early testing so far no issues.  Thank you to the team for all of your great work!

@Graeme: I'll keep on eye on my scheduled tasks and will provide an update tomorrow.

[mtoss]

My gold standard is 10.10.7.
I run jellyfin in docker on synology nas 718+ with 8 gb RAM.
After upgrade to 12RC2 I find it took longer to scan media files. When it comes to iptv m3u streams I have to say that it does not work as good.
Good news is that this new version brings what many of us wanted for years - configurable slideshow photo delay.

[HokieRulz]

@Graeme All of my scheduled tasks did finally run on my v12.0rc2 development instance.  The "last ran" for many of my scheduled tasks did look odd for a while because I had restored a backup taken over the weekend of my Jellyfin v10.11.11 prod instance, restored it to my dev server, and then upgraded to v12.0rc2.  As a result, many of my tasks said "last ran 5 days ago". 

I thought they would run quickly, but apparently when the only trigger is only to run after a time period (like "every 24 hours"), then they don't start based on the last run, but instead ran only after the jellyfin server instance had been running continuously for that amount of time.   

Ok, so my "Refresh People" task hasn't run yet - but it is set to only run every 168 hours!

[foxhollow]

RC2 breaks part of the androidtv client

I am running ubuntu 26.04 with all updates applied (nightly script)
I have been running JF for a few years and always apply latest versions
I have a large video library with nested Movie folders

example: 
/Movies  shared as "Movies"
/Movies/Group1 shared as "Group1"
/Movies/Group2 shared as "Group2"

OK: The JF web server sees the 3 libraries on the home screen and all 3 have files
OK: The Wholphin v1.0.2 android client sees all 3 folders with videos
NOT-OK: Jellyfin app v0.19.9 until recently saw everything but now the Group1 and Group2 folders are empty.

Something has changed and has broken the androidTV client from being able to see the content on those subfolders.

btw: If I search for a movie, it is found and played.  This is obviously a display issue with AndroidTV interacting with RC2

[toytown]

I'm still seeing the same UI lockup happening that occurred on RC1. Basically the UI dashboard is quick. But clicking libraries then sets of a task which locks up most of the UI and jellyfin becomes unresponsive. Even just clicking "Logs" in the admin dashboard takes 1m30s. There is nothing in the log files to indicates what happens.

https://streamable.com/20uzzn

[Kandy]

Have you opened a ticket about this? I haven't had any issues like this on the unstable branch

[theguymadmax]

General advice to everyone: these announcement threads are usually ignored and should not be used for troubleshooting - there is a dedicated troubleshooting section. If you have an issue, create a post with your server details and logs.