ProgressEvent: total property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since ⁨July 2015⁩.

Note: This feature is available in Web Workers.

The ProgressEvent.total read-only property is a number indicating the total size of the data being transmitted or processed.

For ProgressEvents dispatched by the browser, the value refers to the size, in bytes, of a resource and is derived from the Content-Length response header.

In a ProgressEvent you create yourself, this may also be the total bytes of a resource, although this can be any number. For example, you may wish to normalize total to a value such as 100 or 1 if revealing the precise amount of bytes of a resource is a concern. If using 1 as a total, then ProgressEvent.loaded would be a decimal value between 0 and 1.

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