A post that is the same or inferior to an already existing post. This tag only applies to inferior posts that were uploaded after an already existing identical post.
Duplicates should not be confused for the following:
image sample, a compressed or downscaled image typically used by sites to load images faster.
md5 mismatch, an post that has a different md5 from the file at the source.
revision, a post that has been revised by the artist from a previous version.
variant set, posts with a similar base, but non-trivial differences.
scan, a post that has been scanned from another source.
cropped, an image that is a smaller part of another that may be publicly available or through payment.
Before you upload something, check if it has already been uploaded by using the IQDB image search or the "Find similar" button.
Duplicates must be tagged manually. There is no automated system in place to accurately tag duplicates given how easy it is to confuse them for the above (with exception to image samples where the original is already uploaded). Pixel-perfect duplicate may be added automatically to new posts unconditionally; refer to its wiki on how to check for them or how to dispute an automatic addition of the tag.
Guidelines
Do not flag a duplicate post for deletion if your only reason is that the post is a duplicate. Parent them to the superior image instead.
Avoid uploading visually identical posts. If such a post is uploaded, take proper care to tag and parent it correctly.
Check for differences with DuplicateBooru if you are unable to confirm with your own eyes.
Filesize alone does not determine the superiority of an image. For example, for a jpeg with the same resolution as another, the one with less artifacts is superior.
help:post relationships may provide some guidance on how to determine which post is superior.
