A failed screenshot upload in App Store Connect is almost always a concrete image problem rather than an Apple-side block, and the two most common causes are an alpha channel in a PNG and the wrong exact pixel dimensions. App Store Connect rejects screenshots that contain transparency, so if your PNG has an alpha channel you need to flatten it or export it without transparency, or save it as JPEG, which has no alpha. It also requires the exact pixel dimensions for each device size, so a 6.5-inch image will fail in a 6.7-inch slot, and being off by even one pixel is rejected. Accepted formats are PNG and JPEG, and you upload one to ten screenshots per size.
Short answer
Upload failures come down to the image not meeting a specific requirement, and you fix them by correcting the file. Per Apple's screenshot specifications, screenshots must be in .png, .jpg, or .jpeg format and match the exact pixel dimensions for the device display size, for example 1260 by 2736 for a 6.9-inch iPhone in portrait. The two most frequent blockers are an alpha channel, which you remove by flattening the image or saving as JPEG, and wrong dimensions, which you fix by exporting at the exact required size. Apple also notes on the product page that screenshots represent your app, and if exact sizes are not provided it scales from the 6.9-inch set.
What upload failed usually means
When App Store Connect rejects a screenshot, it is telling you the file does not meet a specification, not that your account or app is in trouble. The uploader validates each image against format, dimension, and content rules before it is saved, so a failure happens immediately and specifically. That is good news, because it means the fix is almost always editing or re-exporting the image rather than contacting Apple or waiting.
The causes are a short, predictable list: a transparent alpha channel, the wrong pixel dimensions, the wrong device slot, an unsupported format or color space, a file that is too large or corrupt, or an occasional transient upload hiccup. Knowing that the problem is the image lets you work through those causes methodically. The rest of the sections take the two big ones first, alpha channel and dimensions, since together they account for most failed uploads, then cover the remaining format and process issues.
Remove the alpha channel
The most common surprise failure is an alpha channel, because App Store Connect does not accept screenshots that contain transparency, and many PNG exports include an alpha channel by default. If your upload fails with a message about an alpha channel, the image has a transparency layer that needs to go, even though the screenshot looks completely opaque to you. The transparency does not have to be visible to be present in the file.
Removing it is straightforward. The simplest route is to save the screenshot as JPEG, which has no alpha channel at all, if you do not need PNG. To keep PNG, flatten the image against a solid background and export without transparency, which most image editors offer as an option. On a Mac you can flatten with the built-in sips tool, and command-line tools like ImageMagick can remove the alpha channel in one step by compositing onto a background and turning alpha off. After removing it, re-export and upload again, and the alpha-channel failure clears.
Match the exact pixel dimensions
The other leading cause is dimensions, because Apple requires an exact pixel size for each device display and rejects anything that does not match precisely. A screenshot that is close but off by a pixel, scaled slightly, or in the wrong orientation will fail. So the fix is to export at the exact required resolution for the size you are targeting, not to resize an image that is nearly right, since resampling often lands a pixel off.
The dimensions differ by device class, and a few are the ones you will use most. The 6.9-inch iPhone is 1260 by 2736 in portrait, and the largest iPad, the 13-inch, is 2064 by 2752 in portrait, with landscape being those values swapped. Older 6.5-inch and 6.7-inch iPhone sizes have their own exact dimensions, which is why they are not interchangeable. The reliable approach is to capture on the correct simulator or device for the size, or to export your design at the exact pixel dimensions Apple lists, so the file matches the slot to the pixel.
Do not upload the wrong size into the wrong slot
A subtle version of the dimension problem is putting a correct image into the wrong size slot, which is where the 6.5-inch versus 6.7-inch versus 6.9-inch confusion bites. Each size slot in App Store Connect expects images at that size's exact dimensions, so a valid 6.5-inch screenshot dropped into the 6.7-inch slot fails because its pixels do not match what that slot requires. The image is fine; it is simply in the wrong place.
The good news is you usually do not need a set for every size. Apple lets you provide screenshots at the largest size, the 6.9-inch iPhone and the 13-inch iPad, and scales them down for smaller displays, so a single well-made large set can cover the range. What you cannot do is mix sizes into the wrong slots. So decide to supply the largest size and let Apple scale, or supply each size exactly, but do not feed one size's pixels into another size's slot.
Format, color, and file rules
Beyond alpha and dimensions, a handful of format rules cause uploads to fail. The file must be PNG or JPEG, so an unusual format or a mislabeled file is rejected. Images should be in the RGB color space rather than CMYK, since a CMYK export from a design tool can fail or look wrong. The image should be a standard, flattened bitmap rather than an interlaced or progressive variant that the uploader dislikes, and it should not carry unusual extra channels beyond the expected color data.
File integrity and size matter too. A corrupt export, a partially written file, or an unusually large image can all cause a failure, so re-exporting a clean copy sometimes resolves an upload that fails for no obvious reason. Keeping to a straightforward PNG-without-alpha or a high-quality JPEG in RGB, at the exact required dimensions, avoids essentially all of these format-level rejections, because it gives the uploader exactly the kind of file it expects.
Common upload-failure causes
Matching the failure to its cause points you at the fix. The table below maps the common ones.
| Cause | How it shows up | Fix |
|---|---|---|
| Alpha channel | Rejected for transparency | Flatten or save as JPEG |
| Wrong dimensions | Rejected for size mismatch | Export at the exact pixel size |
| Wrong size slot | 6.5 image in a 6.7 slot fails | Use the correct slot or the largest size |
| Wrong format or color | Not PNG or JPEG, or CMYK | Re-export as RGB PNG or JPEG |
| Corrupt or oversized file | Fails with no clear reason | Re-export a clean copy |
Read the first two rows first, since an alpha channel and wrong dimensions are behind most failed screenshot uploads.
When it is a transient glitch
Sometimes the image is correct and the upload still fails, which points at a transient problem rather than the file. App Store Connect can hit an intermittent error, especially with several images at once or a slow connection, so a simple retry, a page refresh, or a different browser often succeeds where the first attempt did not. If the web uploader keeps failing on a file you have verified, that is a strong signal to try a different path.
Two reliable alternatives help here. Apple's Transporter app and the App Store Connect API let you upload assets outside the browser, which can get past a flaky web upload and also gives clearer error messages. Before assuming a transient glitch, though, confirm the file really is valid, correct format, no alpha, exact dimensions, since a genuine spec problem will fail on every path. If a verified file uploads fine through Transporter, the browser was the issue.
Fix checklist
Working through these steps clears almost every failed upload. The checklist below covers them.
| Step | Action | Done? |
|---|---|---|
| Remove alpha | Flatten the image or save as JPEG | [ ] |
| Check dimensions | Match the exact pixel size for the device | [ ] |
| Use the right slot | Do not mix sizes into the wrong slot | [ ] |
| Confirm format and color | PNG or JPEG, RGB, flattened | [ ] |
| Re-export a clean file | Rule out a corrupt or oversized image | [ ] |
| Retry or use Transporter | Rule out a transient web upload glitch | [ ] |
The step teams skip most is removing the alpha channel, because a screenshot can look fully opaque while still carrying the transparency layer that fails the upload.
Where a scan fits
Screenshots are listing assets, so a security tool has no role in whether they upload, and it is worth being clear about that boundary.
A scanner like PTKD.com analyzes your app build for security issues such as exposed keys, over-broad permissions, and risky third-party code, mapped to OWASP MASVS. To be clear about the boundary: PTKD does not fix or upload your screenshots, which are image files you prepare and submit in App Store Connect. It is useful for the security side of shipping an app, which is separate from your product page assets.
What to take away
- A failed screenshot upload is an image problem, not an account problem, and the fix is almost always editing or re-exporting the file.
- The most common cause is an alpha channel, since App Store Connect rejects transparency, so flatten the image or save it as JPEG, which has no alpha.
- Screenshots must match the exact pixel dimensions for the device size, such as 1260 by 2736 for a 6.9-inch iPhone, and being off or in the wrong orientation fails.
- Do not put one size into another size's slot, and remember you can supply just the largest size and let Apple scale it down.
- Confirm the file is PNG or JPEG in RGB, re-export if it may be corrupt, and retry or use Transporter for a transient glitch; a tool like PTKD.com is for your build, not your screenshots.
