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File Validation

Updated on Dec 10, 2025

The Upload supports file validation—selected files can be validated against their extensions and size.

Types of Validation

The Upload supports three types of validation:

The following example demonstrates a sample configuration for all the three types of validation.

Razor
    @(Html.Kendo().Upload()
        .Name("files")
        .Async(a => a
            .Save("ChunkSave", "Upload")
            .Remove("Remove", "Upload")
        )
        .Validation(validation => validation
            .AllowedExtensions(new string[] { ".gif", ".jpg", ".png" })
            .MaxFileSize(31457280)
            .MinFileSize(30720)
        )
    )

File Extension

The AllowedExtensions(), which accepts an array of strings listing all file extensions that are allowed. If the user tries to select a file with an extension that is not included in the array, the validation will fail.

Maximum File Size

The MaxFileSize() configuration defines the maximum size in bytes allowed of a file that is intended for upload to the server. If the selected file exceeds the maximum size, a validation error message, such as File size too large., is displayed.

Minimum File Size

Similarly, the MinFileSize() method defines the minimum size in bytes allowed of a file that is intended for upload to the server. If the size of the selected file is less than the minimum size, a validation error message, such as File size too small., is displayed.

Browser Limitations

Internet Explorer versions prior to version 10 provide no information on the file size. As a result, the Upload validation for the MinFileSize() and MaxFileSize() options will not work as expected.

See Also