Fix: Invalid Screenshot Dimensions in App Store Connect

Why this happens

When uploading app screenshots to App Store Connect, you may see the error The dimensions of one or more screenshots are wrong. or Your screenshots can't be saved because one or more have invalid dimensions. This occurs because Apple’s media pipeline checks incoming image files against an explicit list of permissible pixel widths and heights down to the exact pixel. If an image deviates by even a single pixel, the asset uploader rejects it immediately.

This mismatch usually stems from three main causes:

1. Window scaling or display scaling: Grabbing screenshots using macOS window capture shortcuts (Shift + Command + 4) captures desktop display scaling factors or rounded window corners rather than the raw framebuffer of the simulator.
2. Alpha channels or color profile issues: PNG exports containing transparent alpha channels or non-standard color spaces frequently trigger validation failures or get rejected during post-processing.
3. Mismatched aspect ratios across device generations: Attempting to reuse screenshots across device tiers (such as using a 6.1-inch screenshot in a 6.7-inch slot or an iPhone aspect ratio in an iPad slot) fails because App Store Connect does not crop or pad user-submitted artwork to fit target buckets.

How to fix it

1. Match the exact required pixel dimensions

App Store Connect groups screenshots by display size tier. You must supply screenshots for the largest screen in each family your app supports. App Store Connect will automatically scale those images down to smaller device displays unless you opt to supply device-specific overrides.

Verify that your image dimensions match these exact pixel resolutions in portrait (invert width and height for landscape):

If your app supports universal orientation, landscape screenshots must reverse the dimensions (for example, 2796 x 1290 for a 6.7-inch iPhone).

2. Capture native resolution from Xcode Simulator

To ensure screenshots possess exact native hardware resolutions without desktop scaling artifacts, take screenshots directly from the Simulator runtime:

1. Open Xcode and launch your desired target simulator (for example, iPhone 16 Pro Max for the 6.7-inch tier, or iPad Pro 12.9-inch).
2. Navigate to the view you want to present.
3. Press Command + S (or select File > Save Screen from the Simulator menu bar).

Alternatively, capture the screenshot from your terminal using xcrun simctl. This bypasses UI scaling entirely and writes the exact framebuffer resolution to a file:

# Identify booted simulators
xcrun simctl list devices | grep Booted

# Capture a native resolution screenshot to your Desktop
xcrun simctl io booted screenshot ~/Desktop/screenshot_6.7.png

Inspect the output image resolution to confirm it matches the required specifications:

sips -g pixelWidth -g pixelHeight ~/Desktop/screenshot_6.7.png

3. Remove alpha channels and re-encode

App Store Connect does not permit transparent pixels or active alpha channels in app preview screenshots. Even if an image appears completely opaque, an active alpha header inside the PNG structure will cause upload failures.

You can strip the alpha channel from your images in bulk using the built-in macOS sips command-line utility:

# Remove alpha channel and re-save as PNG
sips -s format png --deleteColorManagementProperties --deleteProperty alpha ~/Desktop/screenshot_6.7.png --out ~/Desktop/screenshot_6.7_noalpha.png

To convert all PNG files in a folder into opaque, compliant images with a single shell command:

for file in *.png; do
  sips -s format png --deleteProperty alpha "$file" --out "cleaned_$file"
done

Alternatively, open the image in Preview.app, click File > Export, choose PNG, and uncheck the Alpha checkbox before saving.

4. Add missing legacy simulators for 5.5-inch submissions

If your App Store Connect version requires explicit 5.5-inch screenshots (iPhone 8 Plus style), modern Xcode installations might not list an iPhone 8 Plus simulator by default.

To add the legacy simulator device:

1. In Xcode, select Window > Devices and Simulators (or press Shift + Command + 2).
2. Select the Simulators tab.
3. Click the + (Add) button in the lower-left corner.
4. Set Simulator Name to iPhone 8 Plus.
5. Select iPhone 8 Plus from the Device Type dropdown.
6. Select your installed iOS runtime and click Create.
7. Boot the newly created simulator, launch your app, and press Command + S to generate native 1242 x 2208 screenshots.

How to prevent it

• Use Media Manager inheritance: Provide high-resolution master assets for the 6.7-inch iPhone and 12.9-inch iPad Pro displays. Check the Use 6.7″ Display checkbox on smaller display tabs to allow App Store Connect to derive smaller assets automatically.
• Avoid manual desktop crop tools: Never use macOS screen capture selection (Shift + Command + 4) to grab simulator UI; use the Simulator’s internal capture mechanism (Command + S or xcrun simctl).
• Verify status bars: Ensure the status bar appears clean and without clipped text. Use Xcode Simulator’s clean status bar feature before capturing marketing assets (xcrun simctl status_bar booted override --time "9:41" --batteryState charged --batteryLevel 100).
• Validate dimensions before upload: Run sips -g pixelWidth -g pixelHeight *.png in your asset directory as part of your pre-submission checklist.

FAQ

Do I need to upload screenshots for every single iPhone screen size?

No. Apple’s Media Manager allows you to submit screenshots solely for the highest-resolution displays (6.7-inch iPhone and 12.9-inch iPad Pro). App Store Connect automatically scales these images down for smaller screen sizes unless you want custom artwork for specific legacy devices.

Can I upload JPEG images instead of PNG files to App Store Connect?

Yes. App Store Connect accepts both high-quality JPEG and flattened PNG files. If using JPEG, ensure the color space is sRGB or Display P3 and that image compression artifacts are minimal.

Why does App Store Connect reject screenshots taken on my physical iPhone?

Physical devices with Display Zoom enabled or older models with downsampling (such as the iPhone Plus line rendering at 1080p rather than native 1242p) produce images that do not match Apple’s required asset bucket dimensions. You must turn off Display Zoom or use the Xcode Simulator to capture exact native pixel dimensions.