Classification of user actions/flows that will be perceived as task with discrete performance expectations and settings/configurations that affect the raw performance of those tasks.
Pageload
Metrics
| Term |
Metadata |
Definition |
Relevant Links
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One or two sentences |
- Full definition
- Related tests/coverage
- Results
- User research
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| SpeedIndex |
Visual |
(SI) is a page load performance metric that shows you how quickly the contents of a page are visibly populated. It is the average time at which visible parts of the page are displayed. Expressed in milliseconds, and dependent on the size of the viewport, the lower the score, the better. |
MDN Documentation
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| Contentful SpeedIndex |
Visual |
This metric uses edge detection to calculate the amount of “content” that is visible on each frame. It was designed to have a good metric to measure the amount of text that is visible and ignore the impact of popup or login screens at the end of a page load. |
sitespeed.io documentation
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| Perceptual SpeedIndex |
Visual |
A metric that measures the above-the-fold visual performance of a webpage, while accounting for the layout stability. |
* Perceptual Speed Index (PSI) for measuring above-fold visual performance of webpages
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| Visual Completeness |
Visual |
The point in time when a web browser has finished rendering viewable content in the viewport, but not the entire page. |
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| First Paint event |
Standard |
The time between navigation and when the browser renders the first pixels to the screen, rendering anything that is visually different from what was on the screen prior to navigation. |
MDN documentation
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| First Contentful Paint |
Standard |
How long it takes the browser to render the first bit of content from the DOM providing the first feedback to the user the page is actually loading. |
https://developer.mozilla.org/en-US/docs/Glossary/First_contentful_paint MDN documentation
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| DOMContentLoaded event |
Standard |
A DOM event that is fired once the underlying document has finished being parsed and loaded, but before any of its additional resources (stylesheets, images, subframes) have finished loading. |
MDN documentation
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| Onload event |
Standard |
A DOM event that is fired once the underlying document has finished loading, including all of its stylesheets, images and subframes. This does not include additional resources that start to load due to script. |
MDN Documentation
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| Time to Interactive |
Proposed standard |
(TTI) is a non-standardized web performance 'progress' metric defined as the point in time when the last Long Task finished and was followed by 5 seconds of network and main thread inactivity.
- The page has displayed useful content
- Event handlers are registered for most visible page elements
- When a user interacts with the page, the page consistently responds within 50ms - the user does not experience jank.
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| Cold page load |
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browser started and stabilized/idle, same profile dir as previous, site not loaded or cache cleared |
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| Warm page load |
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browser started and stabilized/idle, same profile dir as previous, site already loaded once, any click-throughs clicked |
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| Reload |
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To re-request the rendering of a document. This may mean re-retrieving the entire document and any of its resources off of the network, or might mean reloading the resources out of a local cache. |
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| Backwards/Forwards navigation |
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| Level 1 cookie blocking |
Tracking Protection |
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| Level 2 cookie blocking |
Tracking Protection |
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| Level 1 content blocking |
Tracking Protection |
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| Level 2 content blocking |
Tracking Protection |
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Responsiveness (mobile vs Desktop)
Scroll
| Term |
Metadata |
Definition |
Relevant Links
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| Checkerboarding |
Metrics |
Checkerboarding occurs when Gecko is unable to paint the viewable portion of a webpage while we're scrolling. Instead, we just paint a color instead of the content. |
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| Velocity |
Metrics |
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| Touch |
Variations |
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| Keyboard |
Variations |
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| Mouse/UI |
Variations |
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Browser
| Term |
Metadata |
Desktop Definition |
Mobile Definition |
Relevant Links
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| Pageload Jank |
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| Time to first blank |
Open |
The time from process start to display the very first painted frame. On Windows, this is currently a white rectangle, which we consider "first blank" |
N/A |
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| Time to first chrome paint |
Open |
The time from process start to displaying the first frame of the browser UI (not including the content area) |
N/A |
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| Time to settled about:home |
Open |
The time from process start to displaying a fully loaded about:home |
N/A |
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| Fresh profile |
Open |
new profile dir, user.js, first time network requests |
Application process starts for the very first time. This includes onboarding, but no migration. |
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| Cold start |
Open |
The browser is started when it hasn't already been started in this operating system session, so the disk cache is empty. For example, the first time that Firefox starts up after the operating system boots is a cold start. |
Application process is not running. Not a first run, and no onboarding. The application is started either via the homescreen or applink. In GPlay terminology, there's no stored state (i.e. no `onSaveInstanceState` bundles) When the Fenix team measures cold start times, the generally measure from process start to visual completeness of the homescreen. |
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| Warm start |
Open |
The browser starts when a previous instance of the browser was already started and shutdown within the same operating system session. |
Application process is running, but the HomeActivity is not. The application is started either via the homescreen or applink. In GPlay terminology, "warm start" includes many situations and is not well defined. For example, it also includes if the app process is killed but there are `onSaveInstance` state bundles (which seems closer to Cold start)
This is not currently measured by the Fenix team.
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| Hot start |
Open |
Depending on user settings this will either open new window or new tab |
Application process is running, HomeActivity is also running. The application is started either via the homescreen or applink, which brings the HomeActivity to the foreground.
In GPlay terminology, `onTrimMemory` may or may not have been called)
This is not currently measured by the Fenix team.
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| Delete history on close |
Close |
A non-default configuration that has Firefox forget all user browsing history on shut down. |
N/A |
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| From crash |
Session Restore |
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N/A |
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| User initiated |
Session Restore |
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N/A |
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| App link |
Variations |
N/A |
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| With WebExtension->Theme |
Variations |
At least one or more WebExtension themes is installed, and one is enabled. |
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| With WebExtension->Addon |
Variations |
At least one or more WebExtension addon is installed and enabled. |
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| Secure Proxy |
Variations |
The "Firefox Private Network" WebExtension. |
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| Time to interface change complete |
UI |
Click on a "share" button and the delay to when the display is shown. |
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| Open |
Window |
To open a new browser window. |
N/A |
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| Close |
Window |
To close a new browser window. |
N/A |
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| Switch |
Window |
To switch focus from one browser window to another. |
N/A |
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| Resize |
Window |
To resize a browser window. |
N/A |
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| Open |
Tab |
To open a new browser tab. |
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| Close |
Tab |
To close a new browser tab. |
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| Switch |
Tab |
To switch from one browser tab to another within the same window. |
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| Open |
Menu |
To open one of Firefox's built in toolbar menus or context menu. |
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| Close |
Menu |
To close one of Firefox's built in toolbar menus or context menu. |
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| Touch |
Input |
Input from the user via a touchscreen. |
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| Keyboard |
Input |
Input from the user via the keyboard. |
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| Mouse |
Input |
Input from the user via a mouse. |
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Resource
| Term |
Metadata |
Definition |
Relevant Links
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| Memory |
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| Power |
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| CPU |
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| GPU |
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| Disk |
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| Network |
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| App idle in foreground |
Network variations |
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| App idle in background |
Network variations |
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| Audio |
Media |
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| Dropped Frame |
Video |
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| Resolution Change |
Media |
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| Stall length |
Media |
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| AV sync |
Media |
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| Number of stalls |
Media |
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| AV sync |
Media |
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| Time to payback state change |
Media |
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| Real Time Communication (RTC) |
Media |
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| Frame per second (FPS) |
Virtual Reality (VR) |
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| Visual Distortion |
Virtual Reality (VR) |
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| Z-fighting |
Virtual Reality (VR) |
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| Judder |
Virtual Reality (VR) |
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Components
| Term |
Metadata |
Definition |
Relevant Links
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| Graphics |
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| Layout |
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| Parsing |
Javascript |
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| Compilation |
Javascript |
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| Network |
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| DOM |
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| Storage |
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| Media |
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