title: analytics/mediawiki/web_ui_reading_depth
description: >
  Measures reading depth. Events only logged for UAs that support the
  performance `getEntriesByType` API [1] and `now` API [2]

  [1] https://caniuse.com/mdn-api_performance_getentriesbytype
  [2] https://caniuse.com/high-resolution-time
$id: /analytics/mediawiki/web_ui_reading_depth/1.0.0
$schema: https://json-schema.org/draft-07/schema#
type: object
allOf:
  - $ref: /fragment/analytics/common/2.0.0#
  - $ref: /fragment/analytics/web_identifiers/1.0.0#
  - $ref: /fragment/mediawiki/page/common/2.0.0#
required:
  - is_anon
  - skin
  - visibility_listeners_time
  - action
  - page_length
  - session_token
  - access_method
properties:
    is_anon:
      type: boolean
      description: Is the user viewing anonymously?
    skin:
      type: string
      description: Skin being used by reader.
    total_length:
      type: integer
      description: >
        Total length of time (in milliseconds) from the
        `visibility_listeners_time` to the point at which the page is unloaded.

        Note that this time may include time that the user has the page hidden.
        If interested in the page's total visible time, see the `visible_length`
        field.
    dom_interactive_time:
      type: integer
      description: >
        Total length of time (in milliseconds) till DOM interactive event which
        is the point at which the browser has finished parsing the HTML and DOM
        construction is complete [1]. Note that the user may or may not be able
        to see any pixels on the screen at this point in time.
        
        Note that this will only be present for UAs that support the
        `PerformanceNavigationTiming` API [2].
        
        [1] <https://developers.google.com/web/fundamentals/performance/critical-rendering-path/measure-crp>.
        [2] <https://caniuse.com/mdn-api_performancenavigationtiming>.
    first_paint_time:
      type: integer
      description: >
        Total length of time (in milliseconds) till first paint which is the
        point at which the first pixels get displayed to the user. Note that
        although at least part of the page is visible to the user at this point
        in time, the user may or may not be able to see the entire page.

        Note that this will only be present for UAs that support the
        `PerformancePaintTiming` API [1].

        [1] https://caniuse.com/mdn-api_performancepainttiming
    visibility_listeners_time:
      type: integer
      description: >
        Total length of time (in milliseconds) till visibility event listeners
        were added to the document which enable the tracking of the page's
        visibility as defined by the `visibilitychange` event [1][2]. This point
        in time is also used as the starting point in the calculation of the
        `total_length` and `visible_length` fields.

        [1] <https://developer.mozilla.org/en-US/docs/Web/API/Document/visibilitychange_event
        [2] https://developer.mozilla.org/en-US/docs/Web/API/Page_Visibility_API
    visible_length:
      type: integer
      description: >
        Total length of time (in milliseconds) from the
        `visibility_listeners_time` to the point at which the page was unloaded
        excluding the total time that the document was "hidden" as defined by
        the Page Visibility API [1].

        [1] https://developer.mozilla.org/en-US/docs/Web/API/Page_Visibility_API
    action:
      type: string
      description: The `pageLoaded event happens once per page view, near the beginning. `pageUnloaded` is sent upon leaving the page (if caught).
      enum:
        - pageLoaded
        - pageUnloaded
    page_length:
      type: integer
      description: Total length of page text.
    session_token:
      type: string
      description: Session token that survives across pages (mw.user.sessionId()), but not browser restarts, used in deterministic user bucketing
    default_sample:
      type: boolean
      description: Default sample group. Set when schema has been initiated by the ReadingDepth test.
    access_method:
      type: string
      description: The method by which the user is accessing the page (i.e. desktop or mobile)
examples:
  - $schema:
      $ref: '#/$id'
    meta:
      stream: mediawiki.web_ui_reading_depth_example
      dt: '2021-11-15T18:10:08.108Z'
    is_anon: true
    skin: minerva
    visibility_listeners_time: 326
    action: pageUnloaded
    page_length: 14804
    session_token: 0560fbfbf12184203f65
    access_method: desktop