diff --git a/public/js/audio-player.js b/public/js/audio-player.js
index 9f69af7..e0f898d 100644
--- a/public/js/audio-player.js
+++ b/public/js/audio-player.js
@@ -7,6 +7,7 @@
 
   function mediaUrl(url) {
     if (!url) return '';
+    if (url.startsWith('data:') || url.startsWith('blob:')) return url;
     const separator = url.includes('?') ? '&' : '?';
     return `${url}${separator}v=${Date.now()}`;
   }
@@ -23,7 +24,6 @@
     load(url) {
       unload();
       if (!url) return;
-
       const audio = element();
       audio.src = mediaUrl(url);
       $(audio).removeAttr('hidden').css('display', 'block');
diff --git a/public/js/slideshow.js b/public/js/slideshow.js
index 588ae68..cd4b2bf 100644
--- a/public/js/slideshow.js
+++ b/public/js/slideshow.js
@@ -7,6 +7,7 @@
 
   function mediaUrl(url) {
     if (!url) return '';
+    if (url.startsWith('data:') || url.startsWith('blob:')) return url;
     const separator = url.includes('?') ? '&' : '?';
     return `${url}${separator}v=${Date.now()}`;
   }
diff --git a/test/local-media-display.test.js b/test/local-media-display.test.js
new file mode 100644
index 0000000..265a3db
--- /dev/null
+++ b/test/local-media-display.test.js
@@ -0,0 +1,128 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs/promises';
+import path from 'node:path';
+import test from 'node:test';
+import vm from 'node:vm';
+
+const root = path.resolve(import.meta.dirname, '..');
+
+function createHarness() {
+  const document = {};
+  const elements = new Map();
+
+  function makeElement(id) {
+    if (elements.has(id)) return elements.get(id);
+    const element = {
+      id,
+      attrs: {},
+      css: {},
+      hidden: false,
+      textValue: '',
+      toggled: null,
+      paused: false,
+      loadCount: 0,
+      pause() { this.paused = true; },
+      load() { this.loadCount += 1; },
+      play() { return Promise.resolve(); },
+      removeAttribute(name) {
+        delete this.attrs[name];
+        if (name === 'src') delete this.src;
+      },
+      getAttribute(name) {
+        if (name === 'src') return this.src ?? this.attrs.src ?? null;
+        return this.attrs[name] ?? null;
+      }
+    };
+    elements.set(id, element);
+    return element;
+  }
+
+  class Wrapper {
+    constructor(target) {
+      this.target = target;
+      this[0] = target;
+      this.length = target ? 1 : 0;
+    }
+
+    on() { return this; }
+    off() { return this; }
+    button() { return this; }
+    hide() { if (this.target) this.target.hidden = true; return this; }
+    removeAttr(name) {
+      this.target?.removeAttribute?.(name);
+      if (this.target && name === 'hidden') this.target.hidden = false;
+      return this;
+    }
+    attr(name, value) {
+      if (!this.target) return this;
+      if (value === undefined) return this.target.attrs?.[name];
+      this.target.attrs[name] = String(value);
+      if (name === 'src') this.target.src = String(value);
+      if (name === 'hidden') this.target.hidden = true;
+      return this;
+    }
+    css(name, value) { if (this.target) this.target.css[name] = value; return this; }
+    toggle(value) { if (this.target) this.target.toggled = Boolean(value); return this; }
+    text(value) { if (this.target) this.target.textValue = String(value); return this; }
+    prop(name, value) { if (this.target) this.target[name] = value; return this; }
+    hasClass() { return false; }
+    closest() { return { length: 0 }; }
+  }
+
+  function jquery(target) {
+    if (target === document) return new Wrapper(document);
+    if (typeof target === 'string' && target.startsWith('#')) return new Wrapper(makeElement(target.slice(1)));
+    return new Wrapper(target);
+  }
+
+  const context = {
+    Date,
+    Math,
+    Promise,
+    document,
+    globalThis: null,
+    jQuery: jquery,
+    Wegwichtel: {}
+  };
+  context.globalThis = context;
+  return { context, elements };
+}
+
+async function loadModule(relativePath, harness) {
+  const sourcePath = path.join(root, relativePath);
+  const source = await fs.readFile(sourcePath, 'utf8');
+  vm.runInNewContext(source, harness.context, { filename: sourcePath });
+}
+
+test('audio player preserves local data/blob URLs and cache-busts server URLs', async () => {
+  const harness = createHarness();
+  await loadModule('public/js/audio-player.js', harness);
+
+  const dataUrl = 'data:audio/mpeg;base64,QUJDRA==';
+  harness.context.Wegwichtel.AudioPlayer.load(dataUrl);
+  assert.equal(harness.elements.get('poi-audio').src, dataUrl);
+
+  const blobUrl = 'blob:https://wegwichtel.de/1234';
+  harness.context.Wegwichtel.AudioPlayer.load(blobUrl);
+  assert.equal(harness.elements.get('poi-audio').src, blobUrl);
+
+  harness.context.Wegwichtel.AudioPlayer.load('/api/routes/1/pois/2/audio');
+  assert.match(harness.elements.get('poi-audio').src, /^\/api\/routes\/1\/pois\/2\/audio\?v=\d+$/);
+});
+
+test('slideshow preserves local data/blob URLs and cache-busts server URLs', async () => {
+  const harness = createHarness();
+  await loadModule('public/js/slideshow.js', harness);
+
+  const dataUrl = 'data:image/jpeg;base64,QUJDRA==';
+  harness.context.Wegwichtel.Slideshow.show([{ url: dataUrl, caption: 'Lokal' }]);
+  assert.equal(harness.elements.get('slide-image').src, dataUrl);
+  assert.equal(harness.elements.get('slideshow').toggled, true);
+
+  const blobUrl = 'blob:https://wegwichtel.de/5678';
+  harness.context.Wegwichtel.Slideshow.show([{ url: blobUrl }]);
+  assert.equal(harness.elements.get('slide-image').src, blobUrl);
+
+  harness.context.Wegwichtel.Slideshow.show([{ url: '/api/routes/1/pois/2/pictures/3' }]);
+  assert.match(harness.elements.get('slide-image').src, /^\/api\/routes\/1\/pois\/2\/pictures\/3\?v=\d+$/);
+});