diff --git a/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/InvalidModIdentifier.java b/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/InvalidModIdentifier.java
new file mode 100644
index 000000000..f338d5612
--- /dev/null
+++ b/src/fmllauncher/java/net/minecraftforge/fml/loading/moddiscovery/InvalidModIdentifier.java
@@ -0,0 +1,80 @@
+/*
+ * Minecraft Forge
+ * Copyright (c) 2016-2019.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation version 2.1
+ * of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+package net.minecraftforge.fml.loading.moddiscovery;
+
+import cpw.mods.modlauncher.api.LamdbaExceptionUtils.Supplier_WithExceptions;
+
+import java.nio.file.Path;
+import java.util.Arrays;
+import java.util.Optional;
+import java.util.function.BiPredicate;
+import java.util.zip.ZipFile;
+
+import static cpw.mods.modlauncher.api.LamdbaExceptionUtils.*;
+
+public enum InvalidModIdentifier {
+
+    OLDFORGE(filePresent("mcmod.info")),
+    FABRIC(filePresent("fabric.mod.json")),
+    LITELOADER(filePresent("litemod.json")),
+    OPTIFINE(filePresent("optifine/Installer.class")),
+    INVALIDZIP((f,zf) -> !zf.isPresent());
+
+    private BiPredicate<Path, Optional<ZipFile>> ident;
+
+    InvalidModIdentifier(BiPredicate<Path, Optional<ZipFile>> identifier)
+    {
+        this.ident = identifier;
+    }
+
+    private String getReason()
+    {
+        return "fml.modloading.brokenfile." + this.name().toLowerCase();
+    }
+
+    public static Optional<String> identifyJarProblem(Path path)
+    {
+        Optional<ZipFile> zfo = optionalFromException(() -> new ZipFile(path.toFile()));
+        Optional<String> result = Arrays.stream(values()).
+                                         filter(i -> i.ident.test(path, zfo)).
+                                         map(InvalidModIdentifier::getReason).
+                                         findAny();
+        zfo.ifPresent(rethrowConsumer(ZipFile::close));
+        return result;
+    }
+
+    private static BiPredicate<Path, Optional<ZipFile>> filePresent(String filename)
+    {
+        return (f, zfo) -> zfo.map(zf -> zf.getEntry(filename) != null).orElse(false);
+    }
+
+    private static <T> Optional<T> optionalFromException(Supplier_WithExceptions<T, ? extends Exception> supp)
+    {
+        try
+        {
+            return Optional.of(supp.get());
+        }
+        catch (Exception e)
+        {
+            return Optional.empty();
+        }
+    }
+
+}
diff --git a/src/main/java/net/minecraftforge/fml/ModLoader.java b/src/main/java/net/minecraftforge/fml/ModLoader.java
index b773d5b81..88a71452a 100644
--- a/src/main/java/net/minecraftforge/fml/ModLoader.java
+++ b/src/main/java/net/minecraftforge/fml/ModLoader.java
@@ -35,6 +35,7 @@ import net.minecraftforge.fml.event.lifecycle.ModLifecycleEvent;
 import net.minecraftforge.fml.loading.FMLLoader;
 import net.minecraftforge.fml.loading.FMLPaths;
 import net.minecraftforge.fml.loading.LoadingModList;
+import net.minecraftforge.fml.loading.moddiscovery.InvalidModIdentifier;
 import net.minecraftforge.fml.loading.moddiscovery.ModFile;
 import net.minecraftforge.fml.loading.moddiscovery.ModFileInfo;
 import net.minecraftforge.fml.network.FMLNetworkConstants;
@@ -113,7 +114,8 @@ public class ModLoader
         this.loadingExceptions = FMLLoader.getLoadingModList().
                 getErrors().stream().flatMap(ModLoadingException::fromEarlyException).collect(Collectors.toList());
         this.loadingWarnings = FMLLoader.getLoadingModList().
-                getBrokenFiles().stream().map(file -> new ModLoadingWarning(null, ModLoadingStage.VALIDATE, "fml.modloading.brokenfile", file.getFileName())).collect(Collectors.toList());
+                getBrokenFiles().stream().map(file -> new ModLoadingWarning(null, ModLoadingStage.VALIDATE,
+                    InvalidModIdentifier.identifyJarProblem(file.getFilePath()).orElse("fml.modloading.brokenfile"), file.getFileName())).collect(Collectors.toList());
         LOGGER.info(CORE, "Loading Network data for FML net version: {}", FMLNetworkConstants.NETVERSION);
     }
 
diff --git a/src/main/resources/assets/forge/lang/en_us.json b/src/main/resources/assets/forge/lang/en_us.json
index 6ff40b0dc..aa3f85212 100644
--- a/src/main/resources/assets/forge/lang/en_us.json
+++ b/src/main/resources/assets/forge/lang/en_us.json
@@ -49,6 +49,11 @@
   "fml.modloading.cycle": "Detected a mod dependency cycle: {0}",
   "fml.modloading.failedtoprocesswork":"{0,modinfo,name} ({0,modinfo,id}) encountered an error processing deferred work\n\u00a77{2,exc,msg}",
   "fml.modloading.brokenfile": "File {2} is not a valid mod file",
+  "fml.modloading.brokenfile.oldforge": "File {2} is for an older version of Forge and cannot be loaded",
+  "fml.modloading.brokenfile.liteloader": "File {2} is a LiteLoader mod and cannot be loaded",
+  "fml.modloading.brokenfile.fabric": "File {2} is a Fabric mod and cannot be loaded",
+  "fml.modloading.brokenfile.optifine": "File {2} is OptiFine, which is unsupported",
+  "fml.modloading.brokenfile.invalidzip": "File {2} is not a jar file",
   "fml.modloading.brokenresources": "File {2} failed to load a valid ResourcePackInfo",
 
   "fml.messages.artifactversion.ornotinstalled":"{0,ornull,fml.messages.artifactversion.notinstalled}",