How to Fix the App Store Connect "Wrong Dimensions" Screenshot Error

You drag a set of screenshots into App Store Connect, wait for the upload bar, and get a red banner: the screenshot dimensions are wrong. The images look perfect. They came straight from a design file, or the simulator, and you are certain they are the right size. Yet the upload refuses them. This is one of the most common release-day blockers for iOS developers, and it nearly always has a boring, fixable cause. This guide walks through every reason the error appears, how to diagnose which one you have, and how to produce files that pass first time.

What the error actually means

App Store Connect validates three things when you upload a screenshot: the pixel dimensions, the file format and the presence of transparency. The dimension check is exact. There is no tolerance and no automatic rounding. A 1290 × 2796 image is accepted for the large Dynamic Island iPhone class, but a 1290 × 2797 image is not, even though no human could tell them apart.

The message is also deliberately generic. It does not tell you which of the checks failed or what size it expected. That is why the fastest route to a fix is to ignore the banner and measure the file yourself.

Step 1: Read the real pixel size

Do not trust the frame size in your design tool, the size you typed into an export dialog or the size shown in a file thumbnail. Measure the exported file.

• On macOS, open the image in Preview and choose Tools, then Show Inspector. The Image Dimensions field shows the exact pixel width and height.
• In Finder, select the file and press Command-I. The More Info section lists Dimensions.
• On Windows, right-click the file, choose Properties and open the Details tab.
• In a terminal on macOS, run sips -g pixelWidth -g pixelHeight yourfile.png to print both values.

Write the two numbers down. Now compare them with the accepted sizes for the device class you are uploading to. If they match exactly and the upload still fails, skip ahead to the format and transparency sections.

Step 2: Match the device class

Each upload slot in App Store Connect is tied to a display class. A screenshot that is valid for one class is invalid for another. Here are the accepted portrait sizes that most teams need. Landscape is the same pair reversed.

Two points trip people up. First, Apple requires at least one screenshot in a specific display class on iPhone, which the Apple page describes for the medium Dynamic Island size, so check which slot App Store Connect marks as required for your app rather than assuming. Second, if your app runs on iPad, at least one 13-inch iPad screenshot is required.

The seven most common causes

1. The image is off by one or two pixels

This is the classic. A layer has a soft shadow or a one pixel stroke that extends outside the frame, and the export tool grows the canvas to include it. You get 1291 × 2797 instead of 1290 × 2796. Fix it by clipping the content to the frame, or by cropping the exported file to the exact accepted size.

2. A retina scale factor was applied twice

Exporting a 645 × 1398 frame at 2× gives 1290 × 2796, which is correct. Exporting a 1290 × 2796 frame at 2× gives 2580 × 5592, which is not an accepted size. Check whether the frame in your design file already uses device pixels or points.

3. Wrong display class for the slot

An iPhone Face ID (medium) screenshot uploaded into the Dynamic Island (large) slot has valid pixels for a different class. Upload into the slot that matches, or resize the screenshot to a size listed for the slot you want.

4. Landscape and portrait are swapped

A 2796 × 1290 image is a valid landscape size for the large Dynamic Island class, so confirm that the orientation you are uploading is listed for the slot you are filling.

5. Transparency in the PNG

Apple screenshots should not have an alpha channel. A PNG exported from a design tool with a transparent background may carry alpha even if every visible pixel is opaque. Flatten the image onto a solid color and export again.

6. Wrong file format

Use PNG or JPEG. Formats such as WebP, HEIC or TIFF are not accepted for screenshots, even if macOS previews them without complaint.

7. Screenshots taken from the wrong simulator

A screenshot captured on an iPhone 8 simulator is 750 × 1334, which belongs to the Home Button (medium) class. If you upload it to a large Dynamic Island slot it fails. Capture from a simulator that matches the class you need.

Step 3: Fix the image

There are two sensible ways to change an image to an accepted size, and the right choice depends on what the screenshot contains.

Crop to fill

The image is scaled until it covers the target frame completely, and whatever overflows is trimmed. This works well for marketing artwork with generous margins and for images that are already close to the target aspect ratio. It is a poor choice for a raw app screenshot with a tab bar at the bottom, because the crop can slice off navigation or the status bar.

Pad with a background color

The whole image is kept and scaled to fit inside the target, and the spare space is filled with a solid color. This preserves every pixel of the original interface and is safer for raw screenshots. Choose a color that matches your product page background so the padding looks intentional.

Never stretch a screenshot to fit. A distorted interface is visible, and App Store review can reject screenshots that do not accurately represent the app.

Step 4: Flatten transparency and export

Export as PNG for interface screenshots because it is lossless. If file size is a problem, JPEG at a high quality setting is accepted, but text and thin lines can show compression artifacts, so inspect the result at full size. Before exporting, put a solid background layer behind the artwork so no pixel has any transparency.

Fix it without uploading your screenshots

A quick search for an online screenshot resizer turns up dozens of sites. Most of them upload your file to a server. For unreleased interface, that is a privacy and sometimes a contractual problem, especially for agency work under an NDA.

The free TinyPixels Screenshot Resizer does the whole job in your browser. You drop in your screenshots, choose the exact Apple preset, for example iPhone Dynamic Island (large) 1290 × 2796, and pick crop to fill or pad. You can drag and zoom to choose what stays in frame. The tool exports PNG, flattens transparency where needed and warns you about the issues that cause rejection, then lets you download a single file or a ZIP. Images are processed with the Canvas API on your device, and you can verify that nothing is uploaded by watching the browser's network tab.

Step 5: Re-verify before you upload

1. Re-measure every exported file with Preview, Finder or sips.
2. Confirm each size appears in the accepted list for the class you are filling.
3. Check that the PNG has no transparency. Opening it on a colored background in an image editor will show any holes.
4. Upload a single file first. If it passes, upload the rest.
5. If one file still fails, compare it byte for byte in size with the passing one. Differences point to the setting that changed.

What if the sizes match and it still fails?

Occasionally the pixel size, the format and the transparency are all correct and App Store Connect still complains. The usual explanations are stale browser state and a mismatch between the slot and the size.

• Reload App Store Connect and try again. A stale session can show an old validation result.
• Try a different browser. Browser extensions that rewrite uploads, such as ad blockers or privacy tools, can occasionally interfere.
• Check that you are filling the slot for the correct localization and device class rather than a different tab.
• If Apple has changed its specification for a new device, your size may have moved classes. Re-read the live table.

Reduce screenshot file size after fixing dimensions

Once the dimensions are correct, you may notice the files are heavy. A full iPad PNG can reach several megabytes. Compression does not change the dimensions, so it is safe to run after you have fixed them.

TinyPixels compresses PNG and JPEG screenshots locally on macOS and Windows. Lossless optimization rewrites the file for a smaller size with identical pixels. Lossy quantization can shrink flat interface graphics much further, and you can compare the output against the original before uploading. Because the engine runs on your machine, nothing is sent to a server, and Pro is a one-time purchase rather than a subscription.

Prevent the error next release

• Keep a design template at the exact pixel size of each class you ship, with content clipped to the frame.
• Name exports with the dimensions, such as home-1290x2796.png, so a wrong size is obvious in Finder.
• Add a small script or a checklist item that runs sips on the export folder and compares the sizes with an allow list.
• Store the last good set in version control so you can diff the sizes when something fails.

Conclusion

The wrong dimensions error sounds mysterious, but it is a strict equality check on width and height plus two format rules. Measure the real file, compare it with the accepted size for the right device class, crop or pad to that size, flatten transparency and export as PNG or JPEG. Doing it in a local tool keeps unreleased screens private, and a local compressor keeps the files light.

Frequently asked questions