ID CheckerWebsite: https://www.minecraftforum.net/forums/mapping-and-modding-java-edition/minecraft-mods/1279866-1-0-0-id-checker-v3-resolve-id-conflicts-without
I know what you people will say, "YOU COPIED THIS MOD FROM SHAROSE! HE MADE AN ID RESOLVER!". And my reply is: No, I made my own mod. Sure it may do the same thing, and sure it might look like I copied it, but I didn't. Originally this mod just showed used/free ids for people who were planning on installing more mods so they can configure them beforehand. I got a couple of requests for people on irc to make it able to resolve conflicts and I thought it would be a nice challenge.
For Minecraft 1.0.0