diff --git a/src/app/components/MediaManager.tsx b/src/app/components/MediaManager.tsx
index 3465523..a174b52 100644
--- a/src/app/components/MediaManager.tsx
+++ b/src/app/components/MediaManager.tsx
@@ -781,8 +781,14 @@ export default function MediaManager({ initialPath = '/', rootPath, title, confi
 
     if (!dev.enabled) dev.enabled = 1;
     if (folderConfig?.['base_url']) {
-      dev.base_url = folderConfig['base_url'] === '.' ? path : folderConfig['base_url'];
-      delete dev.url;
+      const resolvedBase = (folderConfig['base_url'] === '.' ? path : folderConfig['base_url']).replace(/\/$/, '');
+      if (mountEntry.path.startsWith(resolvedBase + '/') || mountEntry.path === resolvedBase) {
+        dev.base_url = resolvedBase;
+        dev.url = mountEntry.path.slice(resolvedBase.length) || '/';
+      } else {
+        delete dev.base_url;
+        // dev.url already set to mountEntry.path above
+      }
     }
     if (folderConfig?.['cache'] === '.') dev.cache = path;
     setConfig(newConfig);