About half of all reports are for duplicates and a lot of these are reported wrongly these days, so to hopefully get us all on the same page and save people some time and effort... Wallpapers are merged if the resolutions are the same or almost the same (to a margin of about 5-10%, so a 1920x1280 version would usually be merged with a 1920x1200 one). This is really just to weed out versions like 1920x1081 which are technically not identical to 1080p ones, but are utterly unnecessary. When merging, the oldest wall that's the same or almost the same resolution is what other walls get merged with. There are exceptions to this if
- the older wall is of visibly lower quality
- the older wall has had its original author's watermark removed (wallpaperswide.com and user marks don't count, kids).