{
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          "standard_track": true,
          "deprecated": false
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            },
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              {
                "version_added": "54",
                "notes": "Support for 'Autonomous custom elements' only."
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                "notes": "Support for 'Customized built-in elements' as well."
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                    "type": "preference",
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                  },
                  {
                    "type": "preference",
                    "name": "dom.webcomponents.customelements.enabled",
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                "version_added": "53",
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                "notes": "Support for 'Autonomous custom elements' only."
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                "notes": "Support for 'Customized built-in elements' as well."
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                "notes": "Support for 'Customized built-in elements' as well."
              },
              {
                "version_added": "54",
                "notes": "Support for 'Autonomous custom elements' only."
              }
            ]
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            "standard_track": true,
            "deprecated": false
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        "__compat": {
          "mdn_url": "https://developer.mozilla.org/docs/Web/API/CustomElementRegistry/get",
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                "notes": "Support for 'Customized built-in elements' as well."
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              {
                "version_added": "54",
                "notes": "Support for 'Autonomous custom elements' only."
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            ],
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                "version_added": "66",
                "notes": "Support for 'Customized built-in elements' as well."
              },
              {
                "version_added": "54",
                "notes": "Support for 'Autonomous custom elements' only."
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              {
                "version_added": "79",
                "notes": "Support for 'Customized built-in elements' as well."
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                "version_added": "79",
                "notes": "Support for 'Autonomous custom elements' only."
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                "notes": "Support for 'Customized built-in elements' as well."
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                "version_added": "41",
                "notes": "Support for 'Autonomous custom elements' only."
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                "notes": "Support for 'Customized built-in elements' as well."
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                "version_added": "41",
                "notes": "Support for 'Autonomous custom elements' only."
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              "notes": "Supports 'Autonomous custom elements' but not 'Customized built-in elements'"
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              {
                "version_added": "6.0",
                "notes": "Support for 'Autonomous custom elements' only."
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            ],
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              {
                "version_added": "66",
                "notes": "Support for 'Customized built-in elements' as well."
              },
              {
                "version_added": "54",
                "notes": "Support for 'Autonomous custom elements' only."
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            },
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            "samsunginternet_android": {
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            },
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          },
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            "standard_track": true,
            "deprecated": false
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                "version_added": "66",
                "notes": "Support for 'Customized built-in elements' as well."
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              {
                "version_added": "54",
                "notes": "Support for 'Autonomous custom elements' only."
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            ],
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                "version_added": "66",
                "notes": "Support for 'Customized built-in elements' as well."
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              {
                "version_added": "54",
                "notes": "Support for 'Autonomous custom elements' only."
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            ],
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                "version_added": "79",
                "notes": "Support for 'Customized built-in elements' as well."
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                "version_added": "79",
                "notes": "Support for 'Autonomous custom elements' only."
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            ],
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                    "type": "preference",
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                ]
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            "opera": [
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                "version_added": "53",
                "notes": "Support for 'Customized built-in elements' as well."
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              {
                "version_added": "41",
                "notes": "Support for 'Autonomous custom elements' only."
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            ],
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                "version_added": "47",
                "notes": "Support for 'Customized built-in elements' as well."
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                "version_added": "41",
                "notes": "Support for 'Autonomous custom elements' only."
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                "version_added": "9.0",
                "notes": "Support for 'Customized built-in elements' as well."
              },
              {
                "version_added": "6.0",
                "notes": "Support for 'Autonomous custom elements' only."
              }
            ],
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                "version_added": "66",
                "notes": "Support for 'Customized built-in elements' as well."
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              {
                "version_added": "54",
                "notes": "Support for 'Autonomous custom elements' only."
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            ]
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}