【网站百科】什么是Canonical标签
如果网站中有大量网址形式不同而内容相同的页面，那么从网站seo优化的角度来看，是有问题的。不同的网址都可以访问同样内容的页面，会给有可能引起搜索引擎的误判。Canonical标签的出现，可以尽量这一问题。
其是百度明文规定支持的一种标签，目的是给搜索引擎传达信息：来抓取网站管理者想要呈现的重要内容。
这个标签与301永久重定向有部分功能重合，但也有部分区别，区别如下：
如果想达到几个网址都能访问内容高度一致或完全相同的内容，这很适用于使用Canonical标签，如果只想要某一个特定的网址能访问到目标内容，则使用301永久重定向更为妥当。
具体说明如下：
这两个页面都能访问到“不利于网站seo的几个技术”的相关内容，然而他们的网址形式却不尽相同。搜索引擎是无法分辨哪个网址才是更重要的内容的，如果没有seo优化人员对网址做相应设置，就会造成搜索引擎在目标站点中收录大量的重复内容的问题，长此以往，或者数量级大，就会对网站造成降级处理等惩罚。如何解决？Canonical标签就派上了用场。
“https://www.iyong.com/index.html”
“https://www.iyong.com/index.html#comment-9645″
解决办法是在内容页的头部head标签中，加一段代码：
<link rel=’canonical’ href=’https://www.iyong.com/index.html’ />。
这个标签的意思是告诉搜索引擎，收录Canonical标签指定的url，其他相似，雷同，甚至于完全相同的内容页url需判定为重复内容，这些内容url不参与页面的权值分配。
注：除开百度搜索引擎，其他主流的搜索引擎如谷歌等均支持这个标签的使用。
使用Canonic标签的一些注意事项
1：百度搜索引擎程序还不完善，对于这个标签的支撑还不完美，如果使用该标签，前提是要两个页面完全相同。如果页面雷同或相似，那么通过标签像百度传达页面重要性的成功概率较低。
2：对于百度来讲，如果一个Canonical标签有问题，会不信任该站点的所有Canonical标签（这样来看，百度的技术仍不咋地）.
以上，就是有关Canonical标签的一些说明，从seo优化的角度来讲，利用Canonical标签，可以尽可能解决网站特别是大型网站的内容重复问题。爱用建站支持Canonical标签，并指向用户主域名。
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