分享我的网址时，Facebook Sharer如何选择图片和其他元数据？ [英] How does Facebook Sharer select Images and other metadata when sharing my URL?
问题描述
当使用Facebook Sharer时，Facebook将为用户提供使用从源中提取的一些图像中的1个作为链接预览的选项。如何选择这些图像，如何确保我的页面上的任何特定图像总是包含在此列表中？
当我的页面共享时，我该如何告诉Facebook哪个图像？
Facebook有一组，他们于2010年6月推出，以刷新缓存并排除页面上的任何元标记问题。
此外，页面上的图像必须可以公开访问Facebook抓取工具。您应该指定绝对的网址，如 http://example.com/yourimage.jpg ，而不是仅仅/ yourimage。 JPG。
我可以使用客户端代码（如Javascript或jQuery）更新这些元标记吗？
号很像搜索引擎抓取工具， Facebook刮板不执行脚本，因此当页面下载时，任何元标记都是用于图像选择的元标记。
添加这些标签原因我的网页不再验证。如何解决这个问题？
您可以在标签中添加必要的Facebook命名空间，然后您的页面将通过验证：
< html xmlns =http://www.w3.org/1999/xhtml
xmlns： og =http://ogp.me/ns#
xmlns：fb =https://www.facebook.com/2008/fbml>
When using Facebook Sharer, Facebook will offer the user the option of using 1 of a few images pulled from the source as a preview for their link. How are these images selected, and how can I ensure that any particular image on my page is always included in this list?
How do I tell Facebook which image to use when my page gets shared?
Facebook has a set of open-graph meta tags that it looks at to decide which image to show.
The keys one for the Facebook image are:
<meta property="og:image" content="http://ia.media-imdb.com/rock.jpg"/>
<meta property="og:image:secure_url" content="https://secure.example.com/ogp.jpg" />
and it should be present inside the <head></head> tag at the top of your page.
If these tags are not present, it will look for their older method of specifying an image: <link rel="image_src" href="/myimage.jpg"/>. If neither are present, Facebook will look at the content of your page and choose images from your page that meet its share image criteria: Image must be at least 200px by 200px, have a maximum aspect ratio of 3:1, and in PNG, JPEG or GIF format.
Can I specify multiple images to allow the user to select an image?
Yes, you just need to add multiple image meta tags in the order you want them to appear in. The user will then be presented with an image selector dialog:
I specified the appropriate image meta tags. Why isn't Facebook accepting the changes?
Once a url has been shared, Facebook's crawler, which has a user agent of facebookexternalhit/1.1 (+https://www.facebook.com/externalhit_uatext.php), will access your page and cache the meta information. To force Facebook servers to clear the cache, use the Facebook Url Debugger / Linter Tool that they launched in June 2010 to refresh the cache and troubleshoot any meta tag issues on your page.
Also, the images on the page must be publicly accessible to the Facebook crawler. You should specify absolute url's like http://example.com/yourimage.jpg instead of just /yourimage.jpg.
Can I update these meta tags with client side code like Javascript or jQuery? No. Much like search engine crawlers, the Facebook scraper does not execute scripts so whatever meta tags are present when the page is downloaded are the meta tags that are used for image selection.
Adding these tags causes my page to no longer validate. How can I fix this?
You can add the necessary Facebook namespaces to your tag and your page should then pass validation:
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:og="http://ogp.me/ns#"
xmlns:fb="https://www.facebook.com/2008/fbml">
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![http://example.com/yourimage.jpg](\"http://example.com/yourimage.jpg\"){kind=link}
