ProgressEvent: total property

The ProgressEvent.total read-only property is a 64-bit unsigned integer indicating the total size, in bytes, of the data being transmitted or processed.

When downloading a resource using HTTP, this value is taken from the Content-Length response header. It only counts the body of the HTTP message, and doesn't include headers and other overhead.

If the event's lengthComputable property is false, this value is meaningless and should be ignored.