diff --git a/forge/build.gradle b/forge/build.gradle
index 69b65b9..9e80c6f 100644
--- a/forge/build.gradle
+++ b/forge/build.gradle
@@ -181,6 +181,29 @@ sourceSets.main.java {
     }
 }
 
+// Forge turns every mod jar into a resource pack and reads pack.mcmeta out of
+// it. A jar without one makes Pack.readPackMetadata return null, which Forge
+// raises as ModLoadingStage.ERROR ("fml.modloading.brokenresources") and the
+// game stops on the loading-error screen. The number itself only decides a
+// compatibility warning on a pack the player never sees - these mod packs are
+// merged into the hidden "Mod resources" entry - so an unlisted version
+// falling back to the newest known value costs nothing.
+def packFormats = [
+        '1.14.4': 4,
+        '1.15'  : 5, '1.15.1': 5, '1.15.2': 5,
+        '1.16'  : 5, '1.16.1': 5,
+        '1.16.2': 6, '1.16.3': 6, '1.16.4': 6, '1.16.5': 6,
+        '1.17'  : 7, '1.17.1': 7,
+        '1.18'  : 8, '1.18.1': 8, '1.18.2': 8,
+        '1.19'  : 9, '1.19.1': 9, '1.19.2': 9,
+        '1.19.3': 12, '1.19.4': 13,
+        '1.20'  : 15, '1.20.1': 15, '1.20.2': 18, '1.20.3': 22, '1.20.4': 22,
+        '1.20.5': 32, '1.20.6': 32,
+        '1.21'  : 34, '1.21.1': 34, '1.21.2': 42, '1.21.3': 42, '1.21.4': 46,
+        '1.21.5': 55, '1.21.6': 63, '1.21.7': 64, '1.21.8': 64,
+]
+def packFormat = packFormats[minecraftVersion] ?: packFormats.values().max()
+
 processResources {
     def properties = [
             version              : version,
@@ -195,9 +218,10 @@ processResources {
             minecraft_dependency : minecraftRange,
             loader_version_range : loaderRange,
             mixin_compat         : "JAVA_${target.java}",
+            pack_format          : packFormat,
     ]
     inputs.properties(properties)
-    filesMatching(['META-INF/mods.toml', '*.mixins.json']) {
+    filesMatching(['META-INF/mods.toml', '*.mixins.json', 'pack.mcmeta']) {
         expand(properties)
     }
     // Same reasoning as the source exclusion above: no bootstrap service
diff --git a/forge/src/main/resources/pack.mcmeta b/forge/src/main/resources/pack.mcmeta
new file mode 100644
index 0000000..1744a58
--- /dev/null
+++ b/forge/src/main/resources/pack.mcmeta
@@ -0,0 +1,6 @@
+{
+	"pack": {
+		"description": "${mod_name}",
+		"pack_format": ${pack_format}
+	}
+}
diff --git a/neoforge/build.gradle b/neoforge/build.gradle
index ea73128..0dd0025 100644
--- a/neoforge/build.gradle
+++ b/neoforge/build.gradle
@@ -120,6 +120,29 @@ dependencies {
     neoForge "net.neoforged:neoforge:${target.neoforge}"
 }
 
+// Forge turns every mod jar into a resource pack and reads pack.mcmeta out of
+// it. A jar without one makes Pack.readPackMetadata return null, which Forge
+// raises as ModLoadingStage.ERROR ("fml.modloading.brokenresources") and the
+// game stops on the loading-error screen. The number itself only decides a
+// compatibility warning on a pack the player never sees - these mod packs are
+// merged into the hidden "Mod resources" entry - so an unlisted version
+// falling back to the newest known value costs nothing.
+def packFormats = [
+        '1.14.4': 4,
+        '1.15'  : 5, '1.15.1': 5, '1.15.2': 5,
+        '1.16'  : 5, '1.16.1': 5,
+        '1.16.2': 6, '1.16.3': 6, '1.16.4': 6, '1.16.5': 6,
+        '1.17'  : 7, '1.17.1': 7,
+        '1.18'  : 8, '1.18.1': 8, '1.18.2': 8,
+        '1.19'  : 9, '1.19.1': 9, '1.19.2': 9,
+        '1.19.3': 12, '1.19.4': 13,
+        '1.20'  : 15, '1.20.1': 15, '1.20.2': 18, '1.20.3': 22, '1.20.4': 22,
+        '1.20.5': 32, '1.20.6': 32,
+        '1.21'  : 34, '1.21.1': 34, '1.21.2': 42, '1.21.3': 42, '1.21.4': 46,
+        '1.21.5': 55, '1.21.6': 63, '1.21.7': 64, '1.21.8': 64,
+]
+def packFormat = packFormats[minecraftVersion] ?: packFormats.values().max()
+
 processResources {
     def properties = [
             version              : version,
@@ -135,10 +158,11 @@ processResources {
             loader_version_range : languageRange,
             neoforge_dependency  : neoforgeRange,
             mixin_compat         : "JAVA_${target.java}",
+            pack_format          : packFormat,
     ]
     inputs.properties(properties)
     inputs.property('modsTomlName', modsTomlName)
-    filesMatching(['META-INF/neoforge.mods.toml', '*.mixins.json']) {
+    filesMatching(['META-INF/neoforge.mods.toml', '*.mixins.json', 'pack.mcmeta']) {
         expand(properties)
     }
     filesMatching('META-INF/neoforge.mods.toml') {
diff --git a/neoforge/src/main/resources/pack.mcmeta b/neoforge/src/main/resources/pack.mcmeta
new file mode 100644
index 0000000..1744a58
--- /dev/null
+++ b/neoforge/src/main/resources/pack.mcmeta
@@ -0,0 +1,6 @@
+{
+	"pack": {
+		"description": "${mod_name}",
+		"pack_format": ${pack_format}
+	}
+}