A PJPEG file is a bitmap image created in the Progressive JPEG format (PJPEG). It contains encoded bitmap data so that the downloaded image appears progressively from a blurry picture to the final sharp image. PJPEG files may also fill alternating horizontal lines until the full picture is revealed.

PJPEG files allow image previews to be viewed before the entire image is downloaded. These images were once used by some older web browsers, such as old versions of Microsoft Internet Explorer. However, they are no longer widely supported. You can convert the PJPEG image to a .JPG image by renaming the ".pjpeg" extension to ".jpg" then opening it in a program that supports JPG images, such as Microsoft Photos in Windows or Apple Preview in macOS. You can view the image then export it to a format, such as JPEG or PNG, that is more widely supported. NOTE: Progressive JPEGs are more often seen with the .PJPG extension.