diff --git a/formats/src/main/kotlin/com/jakewharton/diffuse/format/Aar.kt b/formats/src/main/kotlin/com/jakewharton/diffuse/format/Aar.kt
index c36562ca..1d4d85e7 100644
--- a/formats/src/main/kotlin/com/jakewharton/diffuse/format/Aar.kt
+++ b/formats/src/main/kotlin/com/jakewharton/diffuse/format/Aar.kt
@@ -8,6 +8,7 @@ import com.jakewharton.diffuse.io.Input
 
 class Aar private constructor(
   override val filename: String?,
+  val bytecodeVersion: Short?,
   val files: ArchiveFiles,
   val manifest: AndroidManifest,
   val classes: Jar,
@@ -30,7 +31,7 @@ class Aar private constructor(
         val libs = zip.entries
           .filter { it.path.matches(libsJarRegex) }
           .map { it.asInput().toJar() }
-        return Aar(name, files, manifest, classes, libs)
+        return Aar(name, classes.bytecodeVersion, files, manifest, classes, libs)
       }
     }
   }
diff --git a/formats/src/main/kotlin/com/jakewharton/diffuse/format/BinaryFormat.kt b/formats/src/main/kotlin/com/jakewharton/diffuse/format/BinaryFormat.kt
index ace3b124..e9d6cbec 100644
--- a/formats/src/main/kotlin/com/jakewharton/diffuse/format/BinaryFormat.kt
+++ b/formats/src/main/kotlin/com/jakewharton/diffuse/format/BinaryFormat.kt
@@ -1,5 +1,5 @@
 package com.jakewharton.diffuse.format
 
-interface BinaryFormat {
+sealed interface BinaryFormat {
   val filename: String?
 }
diff --git a/formats/src/main/kotlin/com/jakewharton/diffuse/format/Class.kt b/formats/src/main/kotlin/com/jakewharton/diffuse/format/Class.kt
index 603443d1..e04ac23d 100644
--- a/formats/src/main/kotlin/com/jakewharton/diffuse/format/Class.kt
+++ b/formats/src/main/kotlin/com/jakewharton/diffuse/format/Class.kt
@@ -10,6 +10,7 @@ import org.objectweb.asm.MethodVisitor
 import org.objectweb.asm.Opcodes
 
 class Class private constructor(
+  val bytecodeVersion: Short,
   val descriptor: TypeDescriptor,
   val declaredMembers: List<Member>,
   val referencedMembers: List<Member>,
@@ -26,13 +27,14 @@ class Class private constructor(
     @JvmName("parse")
     fun Input.toClass(): Class {
       val reader = ClassReader(toByteArray())
+      val bytecodeVersion = reader.readShort(0 + 6)
       val type = TypeDescriptor("L${reader.className};")
 
       val referencedVisitor = ReferencedMembersVisitor()
       val declaredVisitor = DeclaredMembersVisitor(type, referencedVisitor)
       reader.accept(declaredVisitor, 0)
 
-      return Class(type, declaredVisitor.members.sorted(), referencedVisitor.members.sorted())
+      return Class(bytecodeVersion, type, declaredVisitor.members.sorted(), referencedVisitor.members.sorted())
     }
   }
 }
diff --git a/formats/src/main/kotlin/com/jakewharton/diffuse/format/Jar.kt b/formats/src/main/kotlin/com/jakewharton/diffuse/format/Jar.kt
index 570689a6..61706498 100644
--- a/formats/src/main/kotlin/com/jakewharton/diffuse/format/Jar.kt
+++ b/formats/src/main/kotlin/com/jakewharton/diffuse/format/Jar.kt
@@ -7,6 +7,7 @@ import com.jakewharton.diffuse.io.Input
 
 class Jar private constructor(
   override val filename: String?,
+  val bytecodeVersion: Short?,
   val files: ArchiveFiles,
   val classes: List<Class>,
   override val declaredMembers: List<Member>,
@@ -20,17 +21,27 @@ class Jar private constructor(
     fun Input.toJar(): Jar {
       toZip().use { zip ->
         val files = zip.toArchiveFiles { it.toJarFileType() }
+        val bcVersions = mutableMapOf<Short, Long>()
 
         val classes = zip.entries
+          .asSequence()
           .filter { it.path.endsWith(".class") }
-          .map { it.asInput().toClass() }
+          .map { entry ->
+            entry.asInput().toClass().also { cls ->
+              // Count all the byte code versions in a Jar.
+              bcVersions.merge(cls.bytecodeVersion, 1L, Long::plus)
+            }
+          }
+          .toList()
+
+        val mostBytecodeVersion = bcVersions.maxByOrNull { it.value }?.key
 
         val declaredMembers = classes.flatMap { it.declaredMembers }
         val referencedMembers = classes.flatMapTo(LinkedHashSet()) { it.referencedMembers }
         // Declared methods are likely to reference other declared members. Ensure all are removed.
         referencedMembers -= declaredMembers
 
-        return Jar(name, files, classes, declaredMembers.sorted(), referencedMembers.sorted())
+        return Jar(name, mostBytecodeVersion, files, classes, declaredMembers.sorted(), referencedMembers.sorted())
       }
     }
   }
diff --git a/reports/src/main/kotlin/com/jakewharton/diffuse/report/text/AarDiffTextReport.kt b/reports/src/main/kotlin/com/jakewharton/diffuse/report/text/AarDiffTextReport.kt
index 31f02fc2..4d1bf981 100644
--- a/reports/src/main/kotlin/com/jakewharton/diffuse/report/text/AarDiffTextReport.kt
+++ b/reports/src/main/kotlin/com/jakewharton/diffuse/report/text/AarDiffTextReport.kt
@@ -10,10 +10,16 @@ internal class AarDiffTextReport(private val aarDiff: AarDiff) : Report {
   override fun write(appendable: Appendable) {
     appendable.apply {
       append("OLD: ")
-      appendLine(aarDiff.oldAar.filename)
+      append(aarDiff.oldAar.filename)
+      append(" (bytecodeVersion: ")
+      append(aarDiff.oldAar.bytecodeVersion.toString())
+      appendLine(')')
 
       append("NEW: ")
-      appendLine(aarDiff.newAar.filename)
+      append(aarDiff.newAar.filename)
+      append(" (bytecodeVersion: ")
+      append(aarDiff.newAar.bytecodeVersion.toString())
+      appendLine(')')
 
       appendLine()
       appendLine(
diff --git a/reports/src/main/kotlin/com/jakewharton/diffuse/report/text/JarDiffTextReport.kt b/reports/src/main/kotlin/com/jakewharton/diffuse/report/text/JarDiffTextReport.kt
index 66391f83..895b083b 100644
--- a/reports/src/main/kotlin/com/jakewharton/diffuse/report/text/JarDiffTextReport.kt
+++ b/reports/src/main/kotlin/com/jakewharton/diffuse/report/text/JarDiffTextReport.kt
@@ -10,11 +10,16 @@ internal class JarDiffTextReport(private val jarDiff: JarDiff) : Report {
   override fun write(appendable: Appendable) {
     appendable.apply {
       append("OLD: ")
-      appendLine(jarDiff.oldJar.filename)
+      append(jarDiff.oldJar.filename)
+      append(" (bytecodeVersion: ")
+      append(jarDiff.oldJar.bytecodeVersion.toString())
+      appendLine(')')
 
       append("NEW: ")
-      appendLine(jarDiff.newJar.filename)
-
+      append(jarDiff.newJar.filename)
+      append(" (bytecodeVersion: ")
+      append(jarDiff.newJar.bytecodeVersion.toString())
+      appendLine(')')
       appendLine()
       appendLine(jarDiff.archive.toSummaryTable("JAR", Type.JAR_TYPES))
       appendLine()