Matomo (Piwik) creates cache files during its normal operation. The caches are automatically deleted in Matomo during an upgrade of core, or an upgrade of a plugin. But in some cases it is useful to be able to delete manually.
To delete all cache files used by Matomo, you can run the following command in your Matomo directory:
Alternatively if you don’t have access to the server and command line, you can delete Matomo caches by deleting all the files and directories inside the path/to/piwik/tmp/ folder in Matomo (the tmp/ folder).