compression artifacts

[Verbbaitum]

WTH is compression artifacts? 

[Test Screen Name · Accepted solution]

It comes usually from saving as a JPEG with too strong a compression setting. It also comes from repeated editing of JPEG, since each edit damages it more. If you'd like us to look at your picture, please share the ORIGINAL: we don't work for Adobe and can't see your account.

[Abambo · Accepted solution]

See here: https://en.wikipedia.org/wiki/Compression_artifact