diff --git a/src/lib/storage.js b/src/lib/storage.js
new file mode 100644
index 0000000..7cbc100
--- /dev/null
+++ b/src/lib/storage.js
@@ -0,0 +1,34 @@
+export const DEFAULT_SETTINGS = { apiKey: '', threshold: 5, minViews: 10000 };
+
+const toNumber = (value) => (value === null || value === undefined || value === '' ? NaN : Number(value));
+
+export function normalizeSettings(raw = {}) {
+  const threshold = toNumber(raw.threshold);
+  const minViews = toNumber(raw.minViews);
+  return {
+    apiKey: typeof raw.apiKey === 'string' ? raw.apiKey.trim() : DEFAULT_SETTINGS.apiKey,
+    threshold: Number.isFinite(threshold) && threshold > 0 ? threshold : DEFAULT_SETTINGS.threshold,
+    minViews: Number.isFinite(minViews) && minViews >= 0 ? Math.floor(minViews) : DEFAULT_SETTINGS.minViews,
+  };
+}
+
+export async function getSettings() {
+  const { settings } = await chrome.storage.local.get('settings');
+  return normalizeSettings(settings);
+}
+
+export async function saveSettings(raw) {
+  const settings = normalizeSettings(raw);
+  await chrome.storage.local.set({ settings });
+  return settings;
+}
+
+// Status is { state: 'ok' | 'no-key' | 'invalid-key' | 'quota', message?, until? }.
+export async function getStatus() {
+  const { status } = await chrome.storage.local.get('status');
+  return status ?? { state: 'ok' };
+}
+
+export async function setStatus(status) {
+  await chrome.storage.local.set({ status });
+}
diff --git a/test/storage.test.js b/test/storage.test.js
new file mode 100644
index 0000000..9712546
--- /dev/null
+++ b/test/storage.test.js
@@ -0,0 +1,35 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { DEFAULT_SETTINGS, normalizeSettings } from '../src/lib/storage.js';
+
+test('normalizeSettings falls back to defaults for missing input', () => {
+  assert.deepEqual(normalizeSettings(), DEFAULT_SETTINGS);
+  assert.deepEqual(normalizeSettings({}), DEFAULT_SETTINGS);
+  assert.deepEqual(DEFAULT_SETTINGS, { apiKey: '', threshold: 5, minViews: 10000 });
+});
+
+test('normalizeSettings trims the key and coerces numeric strings', () => {
+  assert.deepEqual(normalizeSettings({ apiKey: '  abc123  ', threshold: '7.5', minViews: '20000' }), {
+    apiKey: 'abc123',
+    threshold: 7.5,
+    minViews: 20000,
+  });
+});
+
+test('normalizeSettings replaces invalid thresholds with the default', () => {
+  for (const threshold of [-1, 0, 'abc', '', null, NaN, Infinity]) {
+    assert.equal(normalizeSettings({ threshold }).threshold, 5, String(threshold));
+  }
+});
+
+test('normalizeSettings replaces invalid minViews with the default and floors decimals', () => {
+  for (const minViews of [-5, 'abc', '', null, NaN]) {
+    assert.equal(normalizeSettings({ minViews }).minViews, 10000, String(minViews));
+  }
+  assert.equal(normalizeSettings({ minViews: 1500.7 }).minViews, 1500);
+  assert.equal(normalizeSettings({ minViews: 0 }).minViews, 0);
+});
+
+test('normalizeSettings ignores a non-string key', () => {
+  assert.equal(normalizeSettings({ apiKey: 12345 }).apiKey, '');
+});