WebPagetest/Page Metrics
Life's too short for slow pages
Contents |
At the top of the main results page as well as the waterfall view is a summary table with metrics about the page load:
Overall Metrics
Load Time
The Load Time will be either the Document Complete Time or Fully Loaded Time depending on how the test was run. If the test was run normally then pagetest will pick the Document Complete Time as the Load Time unless there were more requests after Document Complete than before. It is pretty unusual to have more requests after Document Complete and is usually only encountered in AJAX applications (web mail, mapping applications, etc).
If the test is forced to stop after Document Complete (in the advanced options) then it will always be the Document Complete Time.
First Byte
The First Byte time is the time from when the test started until the response starts coming in for the base page (including the DNS time, socket connect and request time):
If there are redirects in place to get to the base page then those will be included in the time as well:
Start Render
The Start Render time is the time when something non-white is first displayed in the browser window (i.e. the point at which the user is no longer staring at a blank white window). The time is visually represented on the waterfall by a vertical green line:
Document Complete
Document Complete is the point where the page has finished loading (equivalent to when the javascript onLoad event fires for the document). At this point the page is ready for user interaction.
Time
The Document Complete Time is visually represented on the waterfall by a vertical blue line:
Requests
The 'requests' metric is the number of individual requests that were made before the 'Document Complete' (including failed requests and redirects).
Bytes In
The 'Bytes In' metric is a measurement of the number of bytes downloaded for the 'Document Requests'. This includes all of the overhead for HTTP and SSL but does not include the TCP/IP overhead.
Bandwidth
The Bandwidth measurement is a calculation for how efficiently the page bytes are downloaded. It is calculated by dividing the Bytes In measurement by the Bandwidth Time. The Bandwidth Time is the Document Complete Time with the First Byte Time subtracted off:
This is a good way to see how well you are using the available bandwidth. Generally higher bandwidth numbers are better (assuming you have made the page as light as possible).
Fully Loaded
Some pages will request additional objects after the page onload event is fired. Normally there are few if any requests that occur after the page is loaded. WebPagetest will capture the additional objects and their times unless configured to Stop Test at Document Complete
Time
This is the total elapsed time to the point where all browser activity quiesced.
Requests
This is the total number of requests to the point where all browser activity quiesced.
Bytes In
This is the total number of response bytes transmitted from the server to WebPagetest at the point where all browser activity quiesced.
