What is responseEnd?
- responseEnd is the time immediately after the user agent receives the last byte of the current document or immediately before the transport connection is closed, whichever comes first.
- responseEnd is measured regardless of the source (server, relevant application caches or from local resources).
HTTP Request / Response
When a resource is retrieved via the network (rather than the application cache) responseEnd represents part of the HTTP request / response timeline.
The HTTP request / response timeline includes requestStart, responseStart and responseEnd.
Why measure responseEnd?
The responseEnd time represents the very end of the browser retrieving the resource. This means that the browser actually has the resource at this point.
As such, several web performance metrics “end” with responseEnd.
- It is the end time of resource download time.
- It is the end time of any factors other than the browser processing and displaying the resource.
- It is the beginning of browser DOM / rendering factors.
For webmasters it is basically the time where you now can begin determining page speed issues that deal directly with the browser (rendering issues) and the end of the network / retrieval page speed issues (redirects/dns/file size/etc).
What happened just before responseEnd?
Just prior to the responseEnd, the browser began to receive the response (responseStart).
What happens immediately after responseStart?
Assuming all goes well, the next step is the browser parsing / processing the resource. The first step of that is to set the status of the document ready state to “loading”. This means the DOM will start to be built.
The name of the next timestamp will be domLoading