Facebook 的 URL 抓取工具有大小限制吗？我们的网站上有几本书可供下载。那些 HMTL 文件大小低于特定大小 (~390KB) 的文件会被抓取并正确读取，但 4 个较大的文件则不会。这些较大的项目会收到 200 响应代码并打开规范 URL。
所有这些页面都是使用相同的模板构建的，唯一的区别是每本书内容的大小以及每本书与网站上其他页面的链接数量。
- 单击规范 URL
- 在 Firefox 中打开 Firebug 或 Chrome 中的开发者工具到网络选项卡
3, *.html 大小为 >~390KB（对于列出的失败）和
- 点击“准确查看我们的抓取工具在您的网址中看到的内容”
- 失败时显示空白页，成功时显示 HTML
失败：
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftapom.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftapom.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftbgpu.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftbgpu.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fttjc.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fttjc.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftbdse.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftbdse.html
成功案例：
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fthogtc.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fthogtc.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Faabibp.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Faabibp.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftww.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftww.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftsosw.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftsosw.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fsyottc.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fsyottc.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fttigtio.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fttigtio.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Faadac.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Faadac.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fsiud.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Fsiud.html
- https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftuyc.html https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Frcg.org%2Fbooks%2Ftuyc.html
解决您的问题的方法可能是检查是否是真实用户或 Facebook 机器人正在访问您的页面。如果是机器人，则仅为其渲染必要的元数据。您可以通过其用户代理检测机器人，根据Facebook 文档 https://developers.facebook.com/docs/reference/plugins/like/ is:
"facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)"
代码看起来像这样（在 PHP 中）：
function userAgentIsFacebookBot() {
if ($_SERVER['HTTP_USER_AGENT'] == "facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)") {
return true;
}
return false;
}
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