diff --git a/src/mime.js b/src/mime.js
index 3d1d06b..37f3578 100644
--- a/src/mime.js
+++ b/src/mime.js
@@ -9,6 +9,7 @@ const OUTPUT_MIME_TYPES = {
   tiff: 'image/tiff',
   avif: 'image/avif',
   bmp: 'image/bmp',
+  ico: 'image/x-icon',
   pdf: 'application/pdf',
   html: 'text/html',
   txt: 'text/plain',
@@ -39,7 +40,9 @@ const UNDETECTABLE_TEXT_FORMATS = {
 };
 
 function normalizeFormat(format) {
-  return format === 'jpg' ? 'jpeg' : format;
+  if (format === 'jpg') return 'jpeg';
+  if (format === 'heif') return 'heic';
+  return format;
 }
 
 export async function resolveInputFormat(filePath, declaredFormat) {
diff --git a/test/mime.test.js b/test/mime.test.js
index f6175f2..1780bce 100644
--- a/test/mime.test.js
+++ b/test/mime.test.js
@@ -28,6 +28,12 @@ describe('outputMimeType', () => {
   });
 });
 
+describe('outputMimeType — ico', () => {
+  it('returns image/x-icon for ico', () => {
+    expect(outputMimeType('ico')).toBe('image/x-icon');
+  });
+});
+
 describe('resolveInputFormat', () => {
   it('accepts a PNG file declared as png', async () => {
     const fixturePath = path.join(import.meta.dirname, 'fixtures', 'sample.png');
@@ -84,3 +90,17 @@ describe('resolveInputFormat', () => {
     await fs.unlink(fixturePath);
   });
 });
+
+describe('resolveInputFormat — heic/heif alias', () => {
+  it('accepts a HEIC-family file declared as heic', async () => {
+    const fixturePath = path.join(import.meta.dirname, 'fixtures', 'sample.heic');
+    const result = await resolveInputFormat(fixturePath, 'heic');
+    expect(result.valid).toBe(true);
+  });
+
+  it('accepts the same HEIC-family content declared as heif', async () => {
+    const fixturePath = path.join(import.meta.dirname, 'fixtures', 'sample.heif');
+    const result = await resolveInputFormat(fixturePath, 'heif');
+    expect(result.valid).toBe(true);
+  });
+});