diff --git a/benchmark/cleanList.bench.js b/benchmark/cleanList.bench.js
new file mode 100644
index 0000000..ee42b21
--- /dev/null
+++ b/benchmark/cleanList.bench.js
@@ -0,0 +1,119 @@
+const { performance } = require('perf_hooks');
+const { normalizeEntry } = require('../storage.js');
+
+// Current implementation of cleanList (forEach)
+function currentCleanList(list) {
+  let migrated = false;
+  const seen = new Set();
+  const cleaned = [];
+  list.forEach(item => {
+    const norm = normalizeEntry(item);
+    if (norm && !seen.has(norm)) {
+      seen.add(norm);
+      cleaned.push(norm);
+    }
+  });
+  if (cleaned.length !== list.length) {
+    migrated = true;
+  }
+  return cleaned;
+}
+
+// Option A: Standard for loop
+function cleanListForLoop(list) {
+  let migrated = false;
+  const seen = new Set();
+  const cleaned = [];
+  const len = list.length;
+  for (let i = 0; i < len; i++) {
+    const norm = normalizeEntry(list[i]);
+    if (norm && !seen.has(norm)) {
+      seen.add(norm);
+      cleaned.push(norm);
+    }
+  }
+  if (cleaned.length !== len) {
+    migrated = true;
+  }
+  return cleaned;
+}
+
+// Option B: Array.from + Set
+function cleanListArrayFrom(list) {
+  let migrated = false;
+  const seen = new Set();
+  const cleaned = [];
+  for (let i = 0; i < list.length; i++) {
+    const norm = normalizeEntry(list[i]);
+    if (norm && !seen.has(norm)) {
+      seen.add(norm);
+      cleaned.push(norm);
+    }
+  }
+  if (cleaned.length !== list.length) {
+    migrated = true;
+  }
+  return cleaned;
+}
+
+// Option C: Set initialized directly from filtered normalized items
+function cleanListSetFrom(list) {
+  let migrated = false;
+  const cleaned = Array.from(new Set(
+    list
+      .map(normalizeEntry)
+      .filter(Boolean)
+  ));
+  if (cleaned.length !== list.length) {
+    migrated = true;
+  }
+  return cleaned;
+}
+
+function generateDataset(size) {
+  const dataset = [];
+  const sampleArtists = [
+    '  Taylor Swift  ', 'taylor swift', 'DRAKE', 'drake', '  \u200B  Kanye   \u200D WEST  \uFEFF ',
+    'Coldplay', 'COLDPLAY', 'Radiohead    -   Karma   Police', 'The Beatles', '  The Beatles  ',
+    '', '   ', null, undefined, 123
+  ];
+
+  for (let i = 0; i < size; i++) {
+    const sample = sampleArtists[i % sampleArtists.length];
+    dataset.push(sample);
+  }
+  return dataset;
+}
+
+function benchmark(fn, list, iterations = 1000) {
+  for (let i = 0; i < 50; i++) fn(list);
+
+  const start = performance.now();
+  for (let i = 0; i < iterations; i++) {
+    fn(list);
+  }
+  const end = performance.now();
+  return end - start;
+}
+
+function runBenchmarks() {
+  const sizes = [10, 100, 1000, 10000];
+  console.log('=== Performance Benchmarks Comparison ===\n');
+
+  sizes.forEach(size => {
+    const dataset = generateDataset(size);
+    const iterations = size >= 10000 ? 200 : (size >= 1000 ? 2000 : 20000);
+
+    const timeCurrent = benchmark(currentCleanList, dataset, iterations);
+    const timeForLoop = benchmark(cleanListForLoop, dataset, iterations);
+    const timeSetFrom = benchmark(cleanListSetFrom, dataset, iterations);
+
+    console.log(`Dataset size: ${size} items (${iterations} iterations)`);
+    console.log(`  Current (forEach):                 ${timeCurrent.toFixed(3)} ms`);
+    console.log(`  For loop (cleanListForLoop):       ${timeForLoop.toFixed(3)} ms (${((timeCurrent - timeForLoop) / timeCurrent * 100).toFixed(2)}% improvement)`);
+    console.log(`  Array.from(new Set) (SetFrom):     ${timeSetFrom.toFixed(3)} ms (${((timeCurrent - timeSetFrom) / timeCurrent * 100).toFixed(2)}% improvement)`);
+    console.log('');
+  });
+}
+
+runBenchmarks();
diff --git a/storage.js b/storage.js
index b76a74a..5908607 100644
--- a/storage.js
+++ b/storage.js
@@ -59,14 +59,15 @@ function getBlockData() {
         const cleanList = (list) => {
           const seen = new Set();
           const cleaned = [];
-          list.forEach(item => {
-            const norm = normalizeEntry(item);
+          const len = list.length;
+          for (let i = 0; i < len; i++) {
+            const norm = normalizeEntry(list[i]);
             if (norm && !seen.has(norm)) {
               seen.add(norm);
               cleaned.push(norm);
             }
-          });
-          if (cleaned.length !== list.length) {
+          }
+          if (cleaned.length !== len) {
             migrated = true;
           }
           return cleaned;
diff --git a/test/cleanList.test.js b/test/cleanList.test.js
new file mode 100644
index 0000000..63bb0ed
--- /dev/null
+++ b/test/cleanList.test.js
@@ -0,0 +1,88 @@
+const { describe, it, beforeEach } = require('node:test');
+const assert = require('node:assert');
+
+// Setup mock chrome API before loading storage
+let storageData = {};
+let storageSaved = null;
+let lastError = null;
+
+global.chrome = {
+  runtime: {
+    get lastError() { return lastError; }
+  },
+  storage: {
+    sync: {
+      get: (keys, callback) => {
+        const res = {};
+        keys.forEach(k => {
+          if (k in storageData) res[k] = storageData[k];
+        });
+        callback(res);
+      },
+      set: (data, callback) => {
+        storageSaved = data;
+        Object.assign(storageData, data);
+        if (callback) callback();
+      }
+    }
+  }
+};
+
+const { getBlockData, addBlockedItem, removeBlockedItem } = require('../storage.js');
+
+describe('getBlockData and list cleaning / deduplication', () => {
+  beforeEach(() => {
+    storageData = {};
+    storageSaved = null;
+    lastError = null;
+  });
+
+  it('should clean, normalize, and de-duplicate lists correctly', async () => {
+    storageData = {
+      blockedArtists: ['  Taylor Swift  ', 'taylor swift', 'DRAKE', 'drake', ''],
+      blockedSongs: ['song 1', 'SONG 1', '  song 2  ', null, 123],
+      blockedAlbums: ['Album A', 'album a', 'Album B']
+    };
+
+    const data = await getBlockData();
+
+    assert.deepStrictEqual(data.blockedArtists, ['taylor swift', 'drake']);
+    assert.deepStrictEqual(data.blockedSongs, ['song 1', 'song 2']);
+    assert.deepStrictEqual(data.blockedAlbums, ['album a', 'album b']);
+
+    // Should have saved migrated data back to storage because cleanup changed length
+    assert.ok(storageSaved);
+    assert.deepStrictEqual(storageSaved.blockedArtists, ['taylor swift', 'drake']);
+  });
+
+  it('should not mark migrated if lists are already clean and normalized', async () => {
+    storageData = {
+      blockedArtists: ['drake', 'taylor swift'],
+      blockedSongs: ['song 1', 'song 2'],
+      blockedAlbums: ['album a']
+    };
+
+    const data = await getBlockData();
+
+    assert.deepStrictEqual(data.blockedArtists, ['drake', 'taylor swift']);
+    assert.deepStrictEqual(data.blockedSongs, ['song 1', 'song 2']);
+    assert.deepStrictEqual(data.blockedAlbums, ['album a']);
+
+    // No set call if not migrated
+    assert.strictEqual(storageSaved, null);
+  });
+
+  it('should set migrated if undefined lists are returned', async () => {
+    storageData = {};
+
+    const data = await getBlockData();
+
+    assert.deepStrictEqual(data, {
+      blockedArtists: [],
+      blockedSongs: [],
+      blockedAlbums: []
+    });
+
+    assert.ok(storageSaved);
+  });
+});