Photoshop supports just about all popular, and a few obscure image file formats. For files that Photoshop can’t open or edit, Adobe has developed Illustrator. Between these two apps, you’d be hard pressed to find an image you can’t open and edit. The thing is, that a file must open in order for you to edit it. Photoshop at times fails to open PNG, JPG, or GIF files and generates the, ‘unknown or invalid marker’ error. This error appears for perfectly normal files that open in your browser without a problem. The ‘Unknown Or Invalid Marker’ error is caused by an incorrect file extension being used with the image. The error message alone doesn’t offer much help but the fix is very simple; correct the file extension.
I’ve personally observed this error is more likely to appear for images downloaded from the internet. On rare occasion, someone might send you an image that generates the ‘Unknown Or Invalid Marker’ error.
The fix is simple; change the file extension. The file might have a JPG extension but is in fact a PNG file. Browsers will adjust this on the fly when you open the image with them but Photoshop will not. You have to fix the file extension which is pretty easy; change the extension through file rename. The tricky part is knowing which is the correct extension to use.
Interchange PNG And JPG
If you have a JPG, change it to PNG. If you have a PNG, change it to JPG. This will solve most problems but not all of them. For the images that are neither JPG nor PNG, you don’t have time to try each and every image file extension in existence.
Use An App
What you should do is download and install IrfanView. It’s a very powerful, free, image viewer. Open the problematic image with IrfanView and it will automatically tell you there is a problem with the file. It will also detect the correct extension and you need only okay the change.
Once IrfanView has corrected the problem, go ahead and open the image again in Photoshop. The Unknown Or Invalid Marker’ error will be gone.