For the selected script step, the waterfall chart lists every downloaded object in the order requested, and displays a timeline for each object that charts the metrics collected for the object.
After you play back a script, select a step and then select the Waterfall tab.
Each resource downloaded for the step is listed in the waterfall in the order it was requested. Only the final part of an object's URL is displayed; hover over the URL to view the full URL in a tooltip.
The timeline represents the overall download time for the object. The colors in the bar identify the metrics that are reported in the timeline.
Hover over a timeline to display a tooltip with the following information:
- The value for each metric collected, and the color that identifies the metric.
- Network Time
- User Experience Time
- IP Address – The IP address from which the object was downloaded.
- Number of Bytes – The total bytes downloaded.
- Return Code – The object's return code, with a brief definition.
If an object error occurred, it is identified by a red Status code and a red line through the timeline. See Synthetic Classic return codes and error codes for descriptions of the error codes.
These columns can be included in the chart.
- ID – The number assigned to the object to indicate the order in which it was downloaded.
- URL – The object's URL. Only the final part of the URL (e.g. the file name for a downloaded image or stylesheet) is displayed; hover over the URL to view the full URL in a tooltip.
- Service – Whether an object is first-party or third-party content.
- Category – The category of 3rd-party hosts. For 1st-party objects, this column contains a dash to indicate there is no category.
- Owner – For third-party objects, the vendor/owner, e.g., Google, Akamai, or Facebook.
- Domain – The domain that the resource was served from.
- Status – The HTTP status code. Hover over the code to see a short description.
- Protocol – HTTP or HTTPS.
- Size – The object's size in bytes (b) or kilobytes (kb).
- IP Address – The IP address from which the object was downloaded.
- Offset – The time elapsed from the start of page navigation to the object request.
- Metric values – DNS lookup, initial Connection, SSL, Request time,First byte download, Content download.
- Client time – The total download time minus any time spent in network interaction.
- Total time – The total download time including client time and network time.
- Timeline – A graphical representation of the metrics collected for object downloads from the start of page navigation through page complete.
See Filtering the waterfall below for details of selecting columns to display.
Click a column head to sort the waterfall by that column in ascending order. Click a second time to sort in descending order. Click the ID column head to return to the original order.
Viewing header information
To view header information for an object, click the object URL and then click View headers in the popup window.
Filtering the waterfall
Use the controls above the waterfall chart to select the information you want to see in the chart.
Type a string in the Filter for objects and header content field to see only the objects that contain the filter string in their URL. The string can be anywhere in the URL. This field filters the chart based on the full URL, not just on the object name displays in the URL column.
The Presets options automatically select which columns to display:
- Default layout – Include these columns in the waterfall:
- Simple layout – Display all the default columns except for Domain and Size.
- Advanced layout – Display the object data in a table that includes all columns except the timeline.
Select or clear items on the Columns menu to choose the information (columns) to display in the waterfall. The ID and URL columns are displayed by default and can't be removed.
Use the Resources menu to select which object types to include in the waterfall. If no object types are selected in this menu, all types are included.
Select object types in the Highlight menu to quickly find objects in the waterfall. Selected types are highlighted with the color indicated in the menu.
These metrics may be displayed in the waterfall page, either in the header or in the object timeline depending on the columns selected to display.
- Client time—Total time to download the resource (object) minus the network time for the resource: the sum of the gaps when downloading resources on a page, when no network activity is happening—This is page-level client time. Unlike the test-level client time, this metric is not dependent on the Include non-network(client time) in results test setting.
- Connections—The number of TCP/IP connections opened—This value is equal to the number of resources with Initial Connection times in the waterfall chart.
- Content download—The time spent downloading the total content of the object—If the content is downloaded entirely in the first packet received and no additional packets are downloaded, this metric is not reported.
- DNS lookup—The time required to resolve the IP address of the host—This time appears only if the address was resolved.
- Elements—The total number of elements (objects) downloaded—This value matches the number of rows in the waterfall chart.
- First byte download—The time between the end of the request and the arrival of the first packet of the response (All resources report this component.)
- Initial connection—The time to open a TCP/IP connection—This metric is charted only if a TCP/IP connection is established. If the connection is reused for another resource, this metric does not appear in that resource's timeline.
- IP addresses—The number of IP addresses to which connections were made—This value may be equal to or less than the number of connections, because multiple connections can be made to the same IP address.
- Network time—The total time of all network traffic for a page (not the sum of download times for all the resources), from the base page's DNS lookup and end through delivery of the last packet of the last resource, excluding any client processing time—In the waterfall chart, the network time reported for an object is based on the whole step (page), not the object.
- Request time—The time from when an HTTP request is sent to the server until the time the first byte of the response is received
- Size—The total number of bytes downloaded from the web server
- Speed index—The average time in which visible parts of the page are displayed, based on the average of Visually complete—A lower speed index means that most parts of the page are rendered very quickly. This metric is only available for Backbone tests that run on the Chrome 56 Agent.
- SSL—The time to establish an SSL connection
- Start offset—The time elapsed from the start of the page load to when this object began downloading—To indicate the start offset, the timeline is indented from the left edge of the waterfall chart.
- Total time—Total download time, including any client time
- UX time—User experience time: the perceived load time of the page—This is the time it takes for the page to appear loaded to the user although the browser may still be downloading items in the background. It is the total time for the step, from the DNS lookup for the first object downloaded to the last byte downloaded for the last object, including any client processing time. UX time may be equal to or greater than network time if it includes times when there is no network activity. When Include client (non-network) time in results is disabled in the test settings, UX Time is reported as zero. In the waterfall chart, the UX time reported for an object is based on the whole step (page), not the object.
- Visually complete—The total time to render all the content in the browser's visible area, i.e. all the web page content that's visible without scrolling—content "below the fold" and non-visible content does not affect the metric. This metric is only available for Backbone tests that run on the Chrome 56 Agent. It is displayed as a browser event in the waterfall chart.