1# Web Subsystem ChangeLog
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3## cl.web.1 Enabling Rule Change for the Viewport meta Tag
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5**Access Level**
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7Public
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9**Reason for Change**
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11In previous versions, the viewport **\<meta>** tag is enabled or disabled based on the device type. On mobile devices, the tag is enabled, and pages are displayed with a mobile-optimized viewport. On other devices, the tag is disabled, and pages are displayed with a desktop-optimized viewport. This means that the viewport cannot be customized.
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13**Change Impact**
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15The [setCustomUserAgent](../../../application-dev/reference/apis-arkweb/js-apis-webview.md#setcustomuseragent10) API can be used to customize the viewport. Specifically, if the custom user agent does not contain the **Mobile** field, the device is identified as desktop and the viewport **\<meta>** tag is disabled by default; if the custom user agent contains the **Mobile** field, the device is identified as mobile and  and the viewport **\<meta>** tag is enabled by default.
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17This change is a non-compatible change. If the custom user agent is not standards compliant, a web page layout error will occur.
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19**API Level**
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2110
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23**Change Since**
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25OpenHarmony SDK 4.1.3.5
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27**Key API/Component Changes**
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29setCustomUserAgent
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31**Adaptation Guide**
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33Set a standards compliant custom user agent or use the default user agent. You are advised to use [getUserAgent](../../../application-dev/reference/apis-arkweb/js-apis-webview.md#getuseragent) to obtain the default user agent and then define a custom user agent based on the default one.
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