diff --git a/src/main/java/com/dostalgia/UploadResource.java b/src/main/java/com/dostalgia/UploadResource.java
index af22e34..340396e 100644
--- a/src/main/java/com/dostalgia/UploadResource.java
+++ b/src/main/java/com/dostalgia/UploadResource.java
@@ -564,6 +564,46 @@ public class UploadResource {
         return json.getBytes(java.nio.charset.StandardCharsets.UTF_8);
     }
 
+    /** Resolve one CD image per parent directory with best-format priority.
+     *  Priority: .cue > .iso > .ccd > .img > .bin
+     *  js-dos DOSBox (Emscripten) supports .cue natively, but .ccd often fails. */
+    private static List<String> resolveCdImages(List<String> cdImages) {
+        // Group by parent directory
+        java.util.Map<String, java.util.List<String>> byDir = new java.util.LinkedHashMap<>();
+        for (String img : cdImages) {
+            int slashIdx = img.lastIndexOf('/');
+            String parentDir = slashIdx >= 0 ? img.substring(0, slashIdx) : "";
+            byDir.computeIfAbsent(parentDir, k -> new java.util.ArrayList<>()).add(img);
+        }
+        List<String> result = new java.util.ArrayList<>();
+        for (var entry : byDir.entrySet()) {
+            String best = pickBestCdImage(entry.getValue());
+            if (best != null) result.add(best);
+        }
+        result.sort(String::compareTo);
+        return result;
+    }
+
+    private static String pickBestCdImage(java.util.List<String> images) {
+        // Priority: .cue [5] > .iso [4] > .ccd [3] > .img [2] > .bin [1]
+        String best = null;
+        int bestScore = -1;
+        for (String s : images) {
+            String lo = s.toLowerCase();
+            int score = lo.endsWith(".cue") ? 5
+                       : lo.endsWith(".iso") ? 4
+                       : lo.endsWith(".ccd") ? 3
+                       : lo.endsWith(".img") ? 2
+                       : lo.endsWith(".bin") ? 1
+                       : 0;
+            if (score > bestScore) {
+                bestScore = score;
+                best = s;
+            }
+        }
+        return best;
+    }
+
     /** Build config for a CD-only game (no executables on the filesystem). */
     private String buildCdOnlyDosboxConf(List<String> cdImages) {
         StringBuilder sb = new StringBuilder();
@@ -574,27 +614,10 @@ public class UploadResource {
         sb.append("[dos]\nxms=true\nems=true\numb=true\n\n");
         sb.append("[autoexec]\n@echo off\nmount c .\n");
         // Mount CD images as D:, E:, …
-        // Prefer descriptor formats (.cue, .ccd) over raw data (.img, .bin)
-        // DOSBox needs descriptors for proper track layout and filesystem access.
-        Set<String> seenDirs = new java.util.HashSet<>();
+        // Resolve one image per directory with format priority (.cue > .iso > .ccd > .img > .bin)
         char driveLetter = 'D';
-        for (String img : cdImages) {
-            int slashIdx = img.lastIndexOf('/');
-            String parentDir = slashIdx >= 0 ? img.substring(0, slashIdx) : "";
-            if (seenDirs.contains(parentDir)) continue;
+        for (String img : resolveCdImages(cdImages)) {
             String imgLower = img.toLowerCase();
-            // Skip raw data files when a descriptor exists in the same directory
-            if (imgLower.endsWith(".img") || imgLower.endsWith(".bin")) {
-                boolean hasDescriptor = cdImages.stream().anyMatch(i -> {
-                    int is = i.lastIndexOf('/');
-                    String ip = is >= 0 ? i.substring(0, is) : "";
-                    String il = i.toLowerCase();
-                    return ip.equals(parentDir)
-                        && (il.endsWith(".cue") || il.endsWith(".ccd"));
-                });
-                if (hasDescriptor) continue;
-            }
-            seenDirs.add(parentDir);
             String flags = (imgLower.endsWith(".bin") && !imgLower.endsWith(".cue"))
                 ? " -t cdrom -fs iso" : " -t cdrom";
             sb.append("imgmount ").append(driveLetter).append(" \"").append(img).append("\"").append(flags).append("\n");
@@ -654,28 +677,10 @@ public class UploadResource {
         sb.append("@echo off\n");
         sb.append("mount c .\n");
         // Mount CD images as D:, E:, … so games can find their CD.
-        // Deduplicate by parent directory — prefer descriptor formats (.cue, .ccd)
-        // over raw data formats (.img, .bin). DOSBox needs descriptors for proper
-        // track layout (audio tracks, subchannel data, copy protection).
-        Set<String> seenDirs = new java.util.HashSet<>();
+        // Resolve one image per directory with format priority (.cue > .iso > .ccd > .img > .bin)
         char driveLetter = 'D';
-        for (String img : cdImages) {
-            int slashIdx = img.lastIndexOf('/');
-            String parentDir = slashIdx >= 0 ? img.substring(0, slashIdx) : "";
-            if (seenDirs.contains(parentDir)) continue;
+        for (String img : resolveCdImages(cdImages)) {
             String imgLower = img.toLowerCase();
-            // Skip raw data files when a descriptor exists in the same directory
-            if (imgLower.endsWith(".img") || imgLower.endsWith(".bin")) {
-                boolean hasDescriptor = cdImages.stream().anyMatch(i -> {
-                    int is = i.lastIndexOf('/');
-                    String ip = is >= 0 ? i.substring(0, is) : "";
-                    String il = i.toLowerCase();
-                    return ip.equals(parentDir)
-                        && (il.endsWith(".cue") || il.endsWith(".ccd"));
-                });
-                if (hasDescriptor) continue;
-            }
-            seenDirs.add(parentDir);
             String flags = (imgLower.endsWith(".bin") && !imgLower.endsWith(".cue"))
                 ? " -t cdrom -fs iso" : " -t cdrom";
             sb.append("imgmount ").append(driveLetter).append(" \"").append(img).append("\"").append(flags).append("\n");