rustypipe/notes/AB_Tests.md

A/B-Tests

When YouTube introduces a new feature, it does so gradually. When a user creates a new session, YouTube decided randomly which new features should be enabled.

YouTube sessions are identified by the visitor data cookie. This cookie is sent with every API request using the context.client.visitor_data JSON parameter. It is also returned in the responseContext.visitorData response parameter and stored as the __SECURE-YEC cookie.

By sending the same visitor data cookie, A/B tests can be reproduced, which is important for testing alternative YouTube clients.

This page lists all A/B tests that were encountered while maintaining the RustyPipe client.

Impact rating:

The impact ratings shows how much effort it takes to adapt alternative YouTube clients to the new feature.

• 🟢 Low Minor incompatibility (e.g. parameter name change)
• 🟡 Medium Extensive changes to the response data model OR removal of parameters
• 🔴 High Changes to the functionality of YouTube that will require API changes for alternative clients

If you want to check how often these A/B tests occur, you can use the codegen tool with the following command: rustypipe-codegen ab-test <id>.

[1] Attributed text description

• Encountered on: 24.09.2022
• Impact: 🟡 Medium
• Endpoint: next (video details)

YouTube shows internal links (channels, videos, playlists) in the video description as buttons with the YouTube icon. To accomplish this, they completely changed the underlying data model.

The new format uses a string with the entire plaintext content along with a list of "commandRuns" which include the link data and the position of the links within the text.

Note that the position and length parameter refer to the number of UTF-16 characters. If you are implementing this in a language which does not use UTF-16 as its internal string representation, you have to iterate over the unicode codepoints and keep track of the UTF-16 index seperately.

OLD

{
  "videoSecondaryInfoRenderer": {
    "description": {
      "runs": [
        {
          "text": "🎧Listen and download aespa's debut single \"Black Mamba\": "
        },
        {
          "navigationEndpoint": {
            "commandMetadata": {
              "webCommandMetadata": {
                "rootVe": 83769,
                "url": "https://www.youtube.com/redirect?...",
                "webPageType": "WEB_PAGE_TYPE_UNKNOWN"
              }
            },
            "urlEndpoint": {
              "nofollow": true,
              "target": "TARGET_NEW_WINDOW",
              "url": "https://www.youtube.com/redirect?..."
            }
          },
          "text": "https://smarturl.it/aespa_BlackMamba"
        }
      ]
    }
  }
}

NEW

{
  "videoSecondaryInfoRenderer": {
    "attributedDescription": {
      "content": "🎧Listen and download aespa's debut single \"Black Mamba\": https://smarturl.it/aespa_BlackMamba\n🐍The Debut Stage...",
      "commandRuns": [
        {
          "startIndex": 58,
          "length": 36,
          "onTap": {
            "innertubeCommand": {
              "commandMetadata": {
                "webCommandMetadata": {
                  "url": "https://www.youtube.com/redirect?...",
                  "webPageType": "WEB_PAGE_TYPE_UNKNOWN",
                  "rootVe": 83769
                }
              },
              "urlEndpoint": {
                "url": "https://www.youtube.com/redirect?...",
                "target": "TARGET_NEW_WINDOW",
                "nofollow": true
              }
            }
          }
        }
      ]
    }
  }
}

[2] 3-tab channel layout

• Announced: 15.09.2022, https://www.youtube.com/watch?v=czIyqEC4V-s
• Encountered on: 11.10.2022
• Impact: 🔴 High
• Endpoint: browse (channel videos)

YouTube changed their channel page layout, putting livestreams and short videos into separate tabs.

Fetching the videos page now only returns a subset of a channel's videos. To get all videos from a channel, you would have to run up to 3 queries.

Even though it has its disadvantages, the RSS feed is now probably the best way for keeping track of a channel's new uploads.

Additionally the channel tab response model was slightly changed, now using a "RichGridRenderer". Short videos also have their own data models ("reelItemRenderer").

RichGrid

{
  "tabRenderer": {
    "content": {
      "richGridRenderer": {
        "contents": [
          {
            "richItemRenderer": {
              "content": {
                "videoRenderer": {}
              }
            }
          }
        ]
      }
    }
  }
}

Short video

{
  "reelItemRenderer": {
    "accessibility": {
      "accessibilityData": {
        "label": "being smart was my personality trait - 56 seconds - play video"
      }
    },
    "headline": {
      "simpleText": "being smart was my personality trait"
    },
    "navigationEndpoint": {
      "clickTrackingParams": "CLcCEIf2BBgAIhMImuP85t-D-wIVd-sRCB2r6gl7",
      "commandMetadata": {
        "webCommandMetadata": {
          "rootVe": 37414,
          "url": "/shorts/glyJWxp7a5g",
          "webPageType": "WEB_PAGE_TYPE_SHORTS"
        }
      },
      "reelWatchEndpoint": {
        "overlay": {
          "reelPlayerOverlayRenderer": {
            "reelPlayerHeaderSupportedRenderers": {
              "reelPlayerHeaderRenderer": {
                "timestampText": {
                  "simpleText": "2 days ago"
                }
              }
            }
          }
        }
      }
    },
    "thumbnail": {
      "thumbnails": [
        {
          "height": 720,
          "url": "https://i.ytimg.com/vi/glyJWxp7a5g/hq720_2.jpg?sqp=-oaymwEdCJUDENAFSFXyq4qpAw8IARUAAIhCcAHAAQbQAQE=&rs=AOn4CLCUzo9AlrNh4n4cZfTOB8_Gf5aAkw",
          "width": 405
        }
      ]
    },
    "videoId": "glyJWxp7a5g",
    "viewCountText": {
      "simpleText": "593K views"
    }
  }
}

[3] Channel handles in search results

• Encountered on: 20.11.2022
• Impact: 🟡 Medium
• Endpoint: search

Instead of subscriber count / video count, a channel item from the search result now displays the channel handle and the subscriber count. The video count was removed.

The implementation looks pretty quick and dirty, as they did not even bother to rename their response parameters. So this might change again in the future.

Note that channels without handles still use the old data model, even on the same page.

OLD

{
  "subscriberCountText": {
    "accessibility": {
      "accessibilityData": {
        "label": "2.92 million subscribers"
      }
    },
    "simpleText": "2.92M subscribers"
  },
  "videoCountText": {
    "runs": [
      {
        "text": "219"
      },
      {
        "text": " videos"
      }
    ]
  }
}

NEW

{
  "videoCountText": {
    "accessibility": {
      "accessibilityData": {
        "label": "4.03 million subscribers"
      }
    },
    "simpleText": "4.03M subscribers"
  },
  "subscriberCountText": {
    "simpleText": "@MusicTravelLove"
  }
}

[4] Video tab on the Trending page

• Encountered on: 1.04.2023
• Impact: 🟢 Low
• Endpoint: browse (trending videos)

YouTube moved the list of trending videos from the main trending page to a separate tab (Videos).

The video tab is fetched with the params 4gIOGgxtb3N0X3BvcHVsYXI%3D.

This new tab contains two shelves (video lists), the first one labeled "Trending videos" which contains the regular trends and the second one named "Recently trending".

The data model for the video shelves did not change.

OLD

NEW

[5] Page header renderer on the Trending page

• Encountered on: 1.05.2023
• Impact: 🟢 Low
• Endpoint: browse (trending videos)

YouTube changed the header renderer type on the trending page to a pageHeaderRenderer.

OLD

{
  "c4TabbedHeaderRenderer": {
    "avatar": {
      "thumbnails": [
        {
          "height": 100,
          "url": "https://www.youtube.com/img/trending/avatar/trending_avatar.png",
          "width": 100
        }
      ]
    },
    "title": "Trending",
    "trackingParams": "CBAQ8DsiEwiXi_iUht76AhVM6hEIHfgTB2g="
  }
}

NEW

{
  "pageHeaderRenderer": {
    "pageTitle": "Trending",
    "content": {
      "pageHeaderViewModel": {
        "title": {
          "dynamicTextViewModel": { "text": { "content": "Trending" } }
        },
        "image": {
          "contentPreviewImageViewModel": {
            "image": {
              "sources": [
                {
                  "url": "https://www.youtube.com/img/trending/avatar/trending.png",
                  "width": 100,
                  "height": 100
                }
              ]
            },
            "style": "CONTENT_PREVIEW_IMAGE_STYLE_CIRCLE"
          }
        }
      }
    }
  }
}

[6] New Music Discography page

• Encountered on: 13.05.2023
• Impact: 🟡 Medium
• Endpoint: browse (music artist)

YouTube merged the 2 sections for singles and albums on artist pages together. Now there is only a Top Releases section.

YouTube also changed the way the full discography page is fetched, surprisingly making it easier for alternative clients. The discography page now has its own content ID in the format of MPAD<channel id> (Music Page Artist Discography). This page can be fetched with a regular browse request without requiring parameters to be parsed or a visitor data cookie to be set, as it was the case with the old system.

OLD

NEW