Prerendering for Single Page Apps
If you’re using a single page app for a site that’s not behind a login, SEO is an important concern.
Google, Bing, Yandex and other all support Google’s standard for Ajax Crawling.
Normally Google will penalize sites heavily for using “Cloaking”, ie. showing different content to Google than to normal web visitors, but for single page apps they have an exception. When detecting a single page app their crawler will send an
_escaped_fragment_ query parameter in the request, and the origin server can then choose to return a document that represents the content a user will actually see when the single page app is running.
Setting up Prerendering
Netlify comes with built-in prerendering. Enabling it is as simple as checking a box:
Our built-in prerendering service will cache prerendered pages for between 24 and 48 hours; this is not adjustable.
You can also use external prerender services that can automate this for you:
Prerender.io has an open-source version of their service that you can self-host.
Paid accounts may use an external service. If you want to try them, upgrade to a paid account and send us a mail at email@example.com and let us know which service you’re using and its API token, and we’ll get you setup.
How it works
We’ve taken great care to implement support for prerendering in the most efficient manner possible.
When a request hits one of our CDN servers, our CDN software determines if it’s a prerendering request from a crawler. If prerendering is enabled for your site, our cache servers will contact the prerendering backend straight from our CDN nodes instead of serving the normal cached request.
If your prerendering backend makes good use of HTTP caching headers like max-age, ETags or Last-Modified dates, prerendered responses will be cached sensibly on our CDN edge nodes. In our initial tests we’ve seen average response times of ~100ms to crawlers, which is low enough that Google will still give your site a SEO boost for being fast.
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