Hard to Know if Page is Rendered Correctly if CSS Adapts Image Size to Viewport Height
Fetch & Render renders page with a high viewport (~9k pixels), so if a site is using CSS which adapts image size to viewport height then it can make it harder to diagnose if the rest of the page is being rendered correctly.
Increase in GSC 403 Errors Could be Due to CMS Bot or Denial of Service Protection
An influx of 403 Forbidden errors in Search Console could be due bot protection or denial of service protection built in by a site’s host or CMS. This might be triggered if Google fetches a lot of pages in a short space of time. John recommends checking server logs to get a better understanding of what is happening. Fetch & Render can be used to check if Googlebot is blocked from specific URLs.
Fetch & Render Won’t Necessarily Render Whole Page
Fetch and Render tool has cut off and won’t necessarily render the whole page. There is also a cut off for indexing, but this is fairly large (~100mb).
Google Doesn’t Always Crawl Lazy-loaded Images
Google will not always crawl images which are implemented using lazy loading.
Content that Fades in Onload With ~2s Transition is Not Considered Hidden
Content is considered hidden when it is not visible at all. Content which fades in within a couple of seconds during a transition or is slightly transparent is likely to be indexed. You can test a transition using Fetch and Render.
Google renders the page the way it’s shown to the user, so if an ad calls doesn’t actually show an ad, it’s not counted.
Fetch and Render Will Show Rendered HTML
Use Fetch & Render using Smartphone User Agent, Mobile Friendly Testing Tool, and AMP Testing Tool to test for Mobile-first Indexing
The Fetch and Render tool set to use a smartphone user agent, the Mobile Friendly Testing Tool, and the AMP Testing Tool can be used to show you the content Google will use for the mobile-first index.
Fetch as Google Content Shows a More Limited Page Size than Web Search
Fetch as Google is limited to a couple of hundred KBs, which is lower than the amount accepted by Web search.