Better Compatibility Checker Mod FAQ
20 questions players actually ask, answered.
How do I set up Better Compatibility Checker on my server?
Install the mod on both the server and the clients, then have the modpack author edit the config file (bcc-common.toml for Forge or bcc.json for Fabric) to set the modpack name and version. The mod will then compare these values when clients connect.
What do the green checkmark and red X mean on the compatibility screen?
A green checkmark means the modpack project ID and version ID on your client match the server's. A red X means they don't match, so you're likely running a different version of the modpack than the server.
Why do I see a red X when joining my friend's server?
Your client's modpack version doesn't match the server's configured modpack version. Update your modpack to the same version the server is running, or ask the server owner which version to use.
Do I need to install Better Compatibility Checker on the client too?
Yes, for the check to work properly it should be installed on both the server and the client. If it's only on the client, the mod falls back to the standard Forge compatibility implementation.
What happens if the server doesn't have Better Compatibility Checker installed?
If the mod is present on your client but not on the server, it defaults to the standard Forge compatibility checker. You won't get the custom modpack name/version comparison.
Where is the config file for Better Compatibility Checker?
For Forge it's bcc-common.toml, and for Fabric it's bcc.json, both located in the config folder. Modpack authors edit this file to set the modpack name and version.
Can I use Better Compatibility Checker with Fabric?
Yes, the mod supports both Forge and Fabric, though the config file format differs (bcc-common.toml for Forge, bcc.json for Fabric).
Does Better Compatibility Checker affect server performance?
No, it's a lightweight utility that only runs during the connection handshake to compare modpack IDs and versions. It has no noticeable impact on gameplay or server performance.
How do I fix a failed compatibility check when joining a modded server?
Make sure your client modpack version matches the server's. If you're the server owner, verify the modpack name and version in the config file are correct and that all players are using the same modpack version.
Can I disable the compatibility check?
The mod doesn't provide a simple toggle, but if you remove it from the server, clients will fall back to the standard Forge compatibility checker. Server owners can also adjust the config to match their modpack version.
How do I configure better compatibility checker?
Edit bcc-common.toml on Forge or bcc.json on Fabric and set the modpack name and version fields. These values must match between the server and the client for the check to pass.
What does the green checkmark mean?
It means the modpack project ID and version ID on your client match what the server has configured. You're running the same pack version the server expects.
Why am I getting a red X when joining a server?
Your client's configured modpack version doesn't match the server's. Either update your modpack or ask the server admin to confirm the version they set in the config.
Does better compatibility checker work on Fabric?
Yes, it supports both Forge and Fabric. On Fabric you configure it through bcc.json instead of the TOML file.
What happens if the mod isn't installed on the server?
It falls back to the standard Forge compatibility check. You won't get the custom green check or red X behavior from this mod.
Do I need this mod on both client and server?
For the custom check to work, it needs to be present on both sides. If only the client has it, the server uses its default checker instead.
How do I set the modpack name and version as a modpack author?
Open the config file and fill in the modpack name and version fields to match your published pack. Players running that same version will see the green checkmark.
Will this mod break my server or cause lag?
No, it's a lightweight utility that only affects the compatibility check screen. It doesn't add world content or run heavy background tasks.
Can I use it with a modpack that isn't on CurseForge or Modrinth?
Yes, you just need to set the project ID and version ID manually in the config. The mod compares whatever values you configure, regardless of where the pack is hosted.
Why does the check still fail even though my mods match?
The check compares the configured pack version, not the individual mod list. If the version string in your config differs from the server's, you'll get a red X even with identical mods.