DVD+R DL can be burned in a way that will “fool” most DVD players into thinking it’s a pressed Dual Layer DVD-ROM, so that the disc will play even if the player doesn’t officially support recordable media.
This is a method called BookType bitsetting and most DVD burners will by default use this method when burning DVD+R DL.
DVD-R DL will look like recordable media (because it is) and will make no attempt to “fool” the player. Many older players will not work with Dual Layer recordable media.
Since there are two competing camps for the recordable DVD standards (DVD+R and DVD-R), some of them choose to design their players/recorders to deliberately refuse to work with recordable DVDs using the standard from the opposite camp. Thus you might experience fairly new players that deliberately refuse to play some formats.
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