When you’ve used computers long enough you’ve probably come across some files or folders (henceforth called directories) that don’t look quite right. The names are similar to, though not exactly the same as, other files and directories you have, but they don’t follow the standard naming conventions. Additionally, if you open one of the files, they don’t contain any information that seems useful or relevant. You didn’t make these files and you don’t want them, so what are they and where did they come from? 

These files are CHAFF: Concealed, Hidden, And Forgotten Files. Exactly what these files and directories are and what they do depends on several factors, but they are generally used by the programs that created them as caches, temporary backups of files being edited, or operating system-specific metadata. These files are often hidden unless a user explicitly looks for them or shares data with someone running a different operating system. Thankfully, once they’ve been found, they can usually be deleted safely!

(This deposit consists of a PDF capture of the blog where the article was published and a PDF version of the "preprint.")