Filters the largest file a file upload field accepts, in bytes. Deliberately not bounded by the site’s own PHP upload limits. The browser sends each file straight to the upload endpoint, so `upload_max_filesize` and `post_max_size` have nothing to do with this transfer — clamping to them would cap the field at whatever a cheap host allows for files that host never receives. The bound that does matter is the endpoint’s own, which rejects anything over FILE_FIELD_MAX_UPLOAD_SIZE. So this filter can only lower the limit, never raise it: a larger value would have the field accept a file, show the visitor a size allowance in the “file is too large” message that nothing can honour, and then fail the upload once they had already waited for it. Raising the ceiling means raising it at the endpoint first. The result reaches the browser as the `maxUploadSize` config value, and the “file is too * large” message is built from the same number, so the two cannot disagree.

Filters the highest number of files an author may set a file upload field to. This raises the ceiling rather than setting the count. A field still takes whatever its author chose, so one deliberately set to a single file keeps taking a single file — which is the whole difference between offering more room and overriding everybody’s choice. The editor’s control reads the same number, so what an author is offered is what the site will honour. A field already storing a number above the ceiling is clamped down to it, so removing this filter returns those fields to the default rather than leaving them on a value nothing enforces any more. Bounded by FILE_FIELD_MAX_FILES_ABSOLUTE_LIMIT. Nothing at the receiving end refuses a submission for holding too many files — the endpoint’s per-site budgets log and alert but store the file regardless — so this ceiling is the only thing standing in the way.