No matter what mod you want to use, you need to first get your game into a moddable state. This can be done in two ways:

SRXDBepInExInstaller[github.com]
This tool was made specifically for SRXD. You will have to specify the version of BepInEx you want. The most recent version will not work.
As of writing this, most mods written for SRXD use BepInEx version 5.4.23

The automatic BepInEx installer doesn't check for operating system.
If you are on Windows, you will need to install manually!

If the tool doesn't work or you otherwise aren't using it, you can install BepInEx manually too.

1. Download the correct version (5.4.23.2) from here[github.com]
   (get the version for your operating system. Windows, get the x64 version)
   
2. Extract the files directly in the base directory of Spin Rhythm. This is typically at
   C:\Program Files (x86)\Steam\steamapps\common\Spin Rhythm
   
3. Remove or rename UnityPlayer.dll. You can recover it later by verifying your game files.
   
4. Rename UnityPlayer_Mono.dll to UnityPlayer.dll

Once BepInEx is installed, you will need to launch the game once to generate new folders and files. Once you have, you can check the log, modify the config, and place mods in the newly created Plugins folder.

I recommend looking at the Logging.Console Enabled option. Console is nice for debugging mod issues, but the second window is annoying when trying to navigate windows.

Once BepInEx is installed and you've generated the folders, mod installation is pretty straightforward. Any downloaded mod can be placed directly into the plugins folder. You can also optionally make a subfolder for each mod, but this shouldn't be necessary with how few mods exist for SRXD.

Some mod installation processes vary. You might need to install other dependency mods or get other files that a mod depends on. Individual mods will say if they rely on these dependencies.

Some mods also have config files. You can find and modify them from the config folder.

The true hub for mods is in the SRXD Modding Discord server[discord.gg].
I'll link all the major ones here though.
List last updated 13/11/2024

⠀SpinCore[github.com]

Author: Mew
A general purpose library mod used by many other mods. Adds functionality for custom menus and in-game triggers.

⠀Speen Chroma 2[github.com]

Author: Mew
This mod requires SpinCore
Adds the ability to change the in-game configurable colors during gameplay. Charts with Chroma triggers will work automatically. Can also be used as a passive rainbow fade effect.

See here for a guide on charting with Chroma.
Charts that support Chroma will be tagged with "Speen Chroma 2"

⠀Dynamic Track Speed[github.com]

Author: Mew
This mod requires SpinCore
Adds the ability to change track speed during gameplay. Charts with Speed triggers will work automatically.

See here for a guide on charting with DTS.
Charts that support DTS will be tagged with "Dynamic Track Speed"

⠀Folder Switcher[github.com]

Author: Edge
This mod requires SpinCore
Allows having multiple separate folders for your customs library. Useful for sorting, reducing load times, and creating smaller folders for specific occasions.

⠀EditorChanges[github.com]

Author: Gavi Guy
Adds extra functionality and bugfixes to the in-game editor. Primarily useful for charters interested in invisible and offtrack notes.
See this guide for help on using these note types.

⠀WowSoSecret[github.com]

Author: Mew
This mod requires SpinCore
Allows you to hide your current in-game status from Steam and Discord rich presences. Useful for secret charting projects.

⠀ForceCombo[github.com]

Author: Mew
This mod requires SpinCore
Allows you to configure different fail states and automatic restarting while playing. Useful for grinding for specific scores.

⠀New-FCs[github.com]

Author: tabbyraks
Adds extra indicators in-game for different combo states, such as Perfect+ Full Combo or Great Full Combo.

Please leave a comment or dm me if this list is outdated in any way