The ProgressEvent.lengthComputable read-only property is a Boolean flag indicating if the resource concerned by the ProgressEvent has a length that can be calculated. If not, the ProgressEvent.total property has no significant value. Syntax flag = ProgressEvent.lengthComputable Specifications Specification Status Comment Progress EventsThe definition of 'ProgressEvent.lengthComputable' in that specification. Recommendation Initial definition. Browser compatibility Desktop Mobile Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari Basic support No support (Yes) 3.5 (1.9.1) No support No support No support Feature Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile Basic support No support (Yes) 1.0 (1.9.1) No support No support No support See also The ProgressEvent interface it belongs to.