diff --git a/lib/utils/image_url.dart b/lib/utils/image_url.dart
new file mode 100644
index 0000000..f23812c
--- /dev/null
+++ b/lib/utils/image_url.dart
@@ -0,0 +1,23 @@
+const _cdnHost = 'cdn.zapstore.dev';
+
+/// CDN image variants supported by `cdn.zapstore.dev`.
+enum CdnImageVariant {
+  icon,
+  iconsm,
+  thumbsm,
+  thumblg,
+}
+
+/// Add a CDN image variant only for Zapstore's CDN.
+///
+/// Non-CDN hosts, null/empty values, and unparseable URLs are returned unchanged.
+String? getCdnImageUrl(String? imageUrl, CdnImageVariant variant) {
+  if (imageUrl == null || imageUrl.isEmpty) return imageUrl;
+
+  final uri = Uri.tryParse(imageUrl);
+  if (uri == null || uri.host != _cdnHost) return imageUrl;
+
+  final params = Map<String, String>.from(uri.queryParameters);
+  params['class'] = variant.name;
+  return uri.replace(queryParameters: params).toString();
+}
diff --git a/lib/widgets/app_card.dart b/lib/widgets/app_card.dart
index 2462ef2..c7b93d1 100644
--- a/lib/widgets/app_card.dart
+++ b/lib/widgets/app_card.dart
@@ -7,6 +7,7 @@ import 'package:markdown/markdown.dart' as md;
 import 'package:skeletonizer/skeletonizer.dart';
 import 'package:zapstore/utils/extensions.dart';
 import 'package:zapstore/utils/nostr_route.dart';
+import 'package:zapstore/utils/image_url.dart';
 import 'package:zapstore/utils/url_utils.dart';
 import 'package:zapstore/services/package_manager/package_manager.dart';
 import 'package:zapstore/widgets/zap_widgets.dart';
@@ -180,7 +181,10 @@ class AppCard extends HookConsumerWidget {
   }
 
   Widget _buildAppIcon(BuildContext context, double size) {
-    final iconUrl = firstValidHttpUrl(app!.icons);
+    final iconUrl = getCdnImageUrl(
+      firstValidHttpUrl(app!.icons),
+      CdnImageVariant.icon,
+    );
 
     return SizedBox(
       width: size,
diff --git a/lib/widgets/app_header.dart b/lib/widgets/app_header.dart
index 364aaa2..46d8b8e 100644
--- a/lib/widgets/app_header.dart
+++ b/lib/widgets/app_header.dart
@@ -4,6 +4,7 @@ import 'package:flutter/material.dart';
 import 'package:gap/gap.dart';
 import 'package:models/models.dart';
 import 'package:zapstore/widgets/version_pill_widget.dart';
+import 'package:zapstore/utils/image_url.dart';
 import 'package:zapstore/utils/url_utils.dart';
 
 class AppHeader extends StatelessWidget {
@@ -13,7 +14,10 @@ class AppHeader extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final iconUrl = firstValidHttpUrl(app.icons);
+    final iconUrl = getCdnImageUrl(
+      firstValidHttpUrl(app.icons),
+      CdnImageVariant.icon,
+    );
 
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
diff --git a/lib/widgets/app_stack_container.dart b/lib/widgets/app_stack_container.dart
index 973cf13..45d311f 100644
--- a/lib/widgets/app_stack_container.dart
+++ b/lib/widgets/app_stack_container.dart
@@ -7,6 +7,7 @@ import 'package:zapstore/utils/nostr_route.dart';
 import 'package:cached_network_image/cached_network_image.dart';
 import 'package:skeletonizer/skeletonizer.dart';
 import '../utils/extensions.dart';
+import '../utils/image_url.dart';
 import '../utils/url_utils.dart';
 import '../theme.dart';
 import '../services/package_manager/package_manager.dart';
@@ -500,7 +501,10 @@ class _AppIconTile extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final iconUrl = firstValidHttpUrl(app.icons);
+    final iconUrl = getCdnImageUrl(
+      firstValidHttpUrl(app.icons),
+      CdnImageVariant.iconsm,
+    );
 
     return Padding(
       padding: const EdgeInsets.all(2),
diff --git a/lib/widgets/common/profile_avatar.dart b/lib/widgets/common/profile_avatar.dart
index e47b4cd..4748134 100644
--- a/lib/widgets/common/profile_avatar.dart
+++ b/lib/widgets/common/profile_avatar.dart
@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:cached_network_image/cached_network_image.dart';
 import 'package:models/models.dart';
+import 'package:zapstore/utils/image_url.dart';
 import 'package:zapstore/utils/url_utils.dart';
 import '../../theme.dart';
 
@@ -42,7 +43,10 @@ class ProfileAvatar extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final pictureUrl = sanitizeHttpUrl(profile?.pictureUrl);
+    final pictureUrl = getCdnImageUrl(
+      sanitizeHttpUrl(profile?.pictureUrl),
+      radius < 24 ? CdnImageVariant.iconsm : CdnImageVariant.icon,
+    );
 
     Widget avatar = ClipOval(
       child: pictureUrl != null
diff --git a/lib/widgets/rounded_image.dart b/lib/widgets/rounded_image.dart
index 981f974..7a457b8 100644
--- a/lib/widgets/rounded_image.dart
+++ b/lib/widgets/rounded_image.dart
@@ -1,5 +1,6 @@
 import 'package:cached_network_image/cached_network_image.dart';
 import 'package:flutter/material.dart';
+import 'package:zapstore/utils/image_url.dart';
 import 'package:zapstore/utils/url_utils.dart';
 
 /// A rounded image widget with fallback to person icon
@@ -10,15 +11,17 @@ class RoundedImage extends StatelessWidget {
     this.url,
     this.size = 22,
     this.radius = 60,
+    this.cdnVariant = CdnImageVariant.iconsm,
   });
 
   final String? url;
   final double size;
   final double radius;
+  final CdnImageVariant cdnVariant;
 
   @override
   Widget build(BuildContext context) {
-    final sanitizedUrl = sanitizeHttpUrl(url);
+    final sanitizedUrl = getCdnImageUrl(sanitizeHttpUrl(url), cdnVariant);
     final fallbackContainer = Container(
       height: size,
       width: size,
diff --git a/lib/widgets/screenshots_gallery.dart b/lib/widgets/screenshots_gallery.dart
index 147a7dc..c642806 100644
--- a/lib/widgets/screenshots_gallery.dart
+++ b/lib/widgets/screenshots_gallery.dart
@@ -3,6 +3,7 @@ import 'package:easy_image_viewer/easy_image_viewer.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:models/models.dart';
+import 'package:zapstore/utils/image_url.dart';
 import 'package:zapstore/utils/url_utils.dart';
 // Local shimmer duplicated to avoid private import
 
@@ -16,6 +17,11 @@ class ScreenshotsGallery extends HookWidget {
     final imageUrls = filterValidHttpUrls(app.images);
     if (imageUrls.isEmpty) return const SizedBox.shrink();
 
+    final thumbUrls = [
+      for (final url in imageUrls)
+        getCdnImageUrl(url, CdnImageVariant.thumbsm)!,
+    ];
+
     final scrollController = useScrollController();
     useListenable(scrollController);
 
@@ -25,9 +31,9 @@ class ScreenshotsGallery extends HookWidget {
         controller: scrollController,
         padding: EdgeInsets.zero,
         scrollDirection: Axis.horizontal,
-        itemCount: imageUrls.length,
+        itemCount: thumbUrls.length,
         itemBuilder: (context, index) {
-          final imageUrl = imageUrls[index];
+          final imageUrl = thumbUrls[index];
           return GestureDetector(
             onTap: () => _showImageViewer(context, imageUrls, index),
             child: Container(
@@ -78,7 +84,11 @@ class ScreenshotsGallery extends HookWidget {
     int initialIndex,
   ) {
     final imageProviders = imageUrls
-        .map((url) => CachedNetworkImageProvider(url) as ImageProvider)
+        .map(
+          (url) => CachedNetworkImageProvider(
+            getCdnImageUrl(url, CdnImageVariant.thumblg)!,
+          ) as ImageProvider,
+        )
         .toList();
 
     showImageViewerPager(
diff --git a/lib/widgets/search_app_card.dart b/lib/widgets/search_app_card.dart
index e9b9904..b36a030 100644
--- a/lib/widgets/search_app_card.dart
+++ b/lib/widgets/search_app_card.dart
@@ -6,6 +6,7 @@ import 'package:models/models.dart';
 import 'package:skeletonizer/skeletonizer.dart';
 import 'package:zapstore/utils/extensions.dart';
 import 'package:zapstore/utils/nostr_route.dart';
+import 'package:zapstore/utils/image_url.dart';
 import 'package:zapstore/utils/url_utils.dart';
 import 'package:zapstore/services/package_manager/package_manager.dart';
 import '../theme.dart';
@@ -27,7 +28,10 @@ class SearchAppCard extends ConsumerWidget {
     final isInstalled =
         ref.watch(installedPackageProvider(app!.identifier)) != null;
 
-    final iconUrl = firstValidHttpUrl(app!.icons);
+    final iconUrl = getCdnImageUrl(
+      firstValidHttpUrl(app!.icons),
+      CdnImageVariant.icon,
+    );
     const iconSize = 48.0;
 
     return GestureDetector(
diff --git a/spec/work/WORK-027-cdn-image-variants.md b/spec/work/WORK-027-cdn-image-variants.md
new file mode 100644
index 0000000..ca18826
--- /dev/null
+++ b/spec/work/WORK-027-cdn-image-variants.md
@@ -0,0 +1,34 @@
+# WORK-027 — CDN Image Variants
+
+**Feature:** (utility parity with webapp `image-url.js`; no FEAT required)
+**Status:** Complete
+
+## Tasks
+
+- [x] 1. Add `getCdnImageUrl` matching webapp logic
+  - Files: `lib/utils/image_url.dart`, `test/utils/image_url_test.dart`
+- [x] 2. Apply variants at image load sites
+  - App icons → `icon` / stack tiles → `iconsm`
+  - Screenshot thumbs → `thumbsm`, lightbox → `thumblg`
+  - Profile/avatar widgets apply icon/iconsm when on CDN (no-op otherwise)
+- [x] 3. Self-review against INVARIANTS.md
+
+## Test Coverage
+
+| Scenario | Expected | Status |
+|----------|----------|--------|
+| CDN URL + variant | `?class=<variant>` appended | [x] |
+| Existing query params | Preserved, `class` set | [x] |
+| Non-CDN / relative / null | Unchanged | [x] |
+
+## Decisions
+
+### 2026-07-16 — Port webapp CDN class param
+
+**Context:** Webapp requests sized variants via `?class=` on `cdn.zapstore.dev`.
+**Decision:** Same helper and call-site mapping in the Flutter app.
+**Rationale:** Smaller transfers for list icons and screenshot thumbs; no-op for other hosts.
+
+## Progress Notes
+
+Mirroring `webapp/src/lib/utils/image-url.js`.
diff --git a/test/utils/image_url_test.dart b/test/utils/image_url_test.dart
new file mode 100644
index 0000000..ad9db8c
--- /dev/null
+++ b/test/utils/image_url_test.dart
@@ -0,0 +1,46 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:zapstore/utils/image_url.dart';
+
+void main() {
+  group('getCdnImageUrl', () {
+    test('adds the requested class to Zapstore CDN URLs', () {
+      expect(
+        getCdnImageUrl('https://cdn.zapstore.dev/file.png', CdnImageVariant.icon),
+        'https://cdn.zapstore.dev/file.png?class=icon',
+      );
+      expect(
+        getCdnImageUrl(
+          'https://cdn.zapstore.dev/file.png',
+          CdnImageVariant.iconsm,
+        ),
+        'https://cdn.zapstore.dev/file.png?class=iconsm',
+      );
+    });
+
+    test('preserves existing query parameters', () {
+      expect(
+        getCdnImageUrl(
+          'https://cdn.zapstore.dev/file.png?x=1',
+          CdnImageVariant.thumbsm,
+        ),
+        'https://cdn.zapstore.dev/file.png?x=1&class=thumbsm',
+      );
+    });
+
+    test('does not transform other hosts or invalid URLs', () {
+      expect(
+        getCdnImageUrl('https://example.com/file.png', CdnImageVariant.icon),
+        'https://example.com/file.png',
+      );
+      expect(
+        getCdnImageUrl('/file.png', CdnImageVariant.icon),
+        '/file.png',
+      );
+    });
+
+    test('returns null and empty unchanged', () {
+      expect(getCdnImageUrl(null, CdnImageVariant.icon), isNull);
+      expect(getCdnImageUrl('', CdnImageVariant.icon), '');
+    });
+  });
+}