Ignoring unmodified files

Black remembers files it has already formatted, unless the --diff flag is used or code is passed via standard input. This information is stored per-user. The exact location of the file depends on the Black version and the system on which Black is run. The file is non-portable. The standard location on common operating systems is:

• Windows: C:\\Users\<username>\AppData\Local\black\black\Cache\<version>\cache.<line-length>.<file-mode>.pickle
• macOS: /Users/<username>/Library/Caches/black/<version>/cache.<line-length>.<file-mode>.pickle
• Linux: /home/<username>/.cache/black/<version>/cache.<line-length>.<file-mode>.pickle

file-mode is an int flag that determines whether the file was formatted as 3.6+ only, as .pyi, and whether string normalization was omitted.

To override the location of these files on macOS or Linux, set the environment variable XDG_CACHE_HOME to your preferred location. For example, if you want to put the cache in the directory you’re running Black from, set XDG_CACHE_HOME=.cache. Black will then write the above files to .cache/black/<version>/.