file

Validates file input constraints: allowed extensions, file size, and number of files.

Options

Option	Type	Default	Description
extension	string	undefined	Comma-separated allowed extensions without dots (e.g. "pdf,jpg,png")
maxSize	number	undefined	Maximum file size in bytes
minFiles	number	undefined	Minimum number of files
maxFiles	number	undefined	Maximum number of files
message	string	locale default	Custom error message

Playground

Valid values

Value	Notes
.jpg file under 5 MB	Extension and size within limits
.jpeg file	Matches allowed extensions

Invalid values

Value	Reason
.exe file	Extension not in allowed list
10 MB .jpg	Exceeds maxSize

Notes

• Empty string ("") always returns valid: true — validators only run on non-empty values. Combine with notEmpty to require a value.
• extension is comma-separated without dots: "pdf,jpg,png".
• maxSize is in bytes: 5 * 1024 * 1024 for 5 MB.