Fixing a Red X When Joining a Modded Server

Understanding What the Red X Means

The red X is not a crash — it is a warning that the modpack project ID or version ID on your client does not match what the server expects. Better Compatibility Checker compares the values the pack author set in the config file (bcc-common.toml on Forge, bcc.json on Fabric) and shows a green checkmark only when both sides agree.

Steps to Resolve the Mismatch

First, confirm you are actually running the same pack version the server advertises. If the server recently updated, download the matching client version rather than trying to patch your old one.

Next, check your own config file. Open config/bcc-common.toml or config/bcc.json and compare the modpack name and version strings against what the server admin says they should be. A trailing space, a capital letter difference, or an old version string is enough to trigger the X.

If your values already match and you still see the X, the server may not have the mod installed at all. In that case the client falls back to the standard Forge check, which can report incompatibility for unrelated reasons. Ask the admin to verify the mod is loaded server-side.

Finally, remember the check is informational — many servers let you join anyway. Treat the X as a prompt to verify versions, not as a hard block.