Pixel is transparent. If the image is not a cockpit, please ensure that locations marked in red are 100% opaque.

Pixel is likely "dirty". If this pixel is within the black background, it is strongly suggested that you clean it.

Pixel is very dark. This level of darkness is "acceptable", but it's strongly suggested that adjustments are made.

Pixel is extremely dark. This level of darkness is "acceptable" so long as the image is not 50% or more this color, or 65% or more of this color and either of the other dark colors.

Hiya! Everyone's favorite mean person here! Unfortunately, running the dirty pixel checker isn't cheap. I really enjoy running it and making sure players are able to check their images easily and bring their images up to quality standards of Combine, but alas, the expenses do build up. Sometime in the near future, I'll be needing to do some upgrades to the server to ensure things continue to run smoothly as well as do some rewriting of the code to improve performance.
If you're willing and able to, please consider shooting me a donation through Paypal. All money received will be used to pay for the server running the dirty pixel checker as well as make improvements through upgrades or code changes.
Worry not, however! Even if I don't get donations, I do intend to continue running the dirty pixel checker for the forseeable future. Please don't feel obligated to donate if you can't or don't want to!