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George Prodromou

The Ultimate Guide to Dynamic Serving

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Ever since Google announced dynamic serving many JavaScript heavy websites have all been considering it. But what exactly is it?

Before we can explain what it is, we first need to fully understand JavaScript websites. Below is an example of a very JavaScript heavy website, where all the content becomes invisible as soon as you disable JavaScript.


The simplest way to understand JavaScript is by thinking of food, yes food! JavaScript off is like purchasing a ready made meal which only requires 10 minutes in the oven to cook, but your oven is broken, meaning you are unable to cook your meal. Whereas JavaScript on, your oven is fully working and you are able to cook your food.

JavaScript websites are rendered on your computer, they are not sent by the server rendered. Your computer does all the hard work of building the page. Therefore, if you disable the primary tool ‘JavaScript’ it cannot build your page, therefore you are left with a blank website.

Search engines such as Google can and do render JavaScript websites, but they usually choose not to do this. Why? rendering a website requires 1,000 if not more resources than crawling a plain HTML website. To put that into perspective, if the internet only had 100,000,000,000 pages (it has way more) and Google had to render every single one of them, it would be equivalent of crawling 10,000,000,000,000 pages. This isn’t very practical for search engines, so they don’t do it!, therefore it is always advised to avoid using JavaScript.

Although Google can render JavaScript websites, they won’t do it often or frequent enough. This means new content can take a while to be indexed and large websites will often find not all of their pages are ever indexed. This is because Google will only render JavaScript websites whenever they have spare resources.

So how can you have a JavaScript heavy websites that’s 100% Google friendly? dynamic serving.

So how does dynamic serving work?

Dynamic serving is serving users and Google different pages in order to satisfy both requirements. For example, a user needs the JavaScript website in order to interact with the website. Whereas Google doesn’t interact with websites therefore does not need a JavaScript page, a static HTML page with all the content visible without executing JavaScript is all that Google requires.


The static website is exactly the same website as the dynamic website. The only difference, you do not need JavaScript in order to see all the content. Going back to our previous example, this is like ordering food to be delivered to your house. It doesn’t matter if your oven/cooker is broken, you are still able to eat, which is the main objective.

Technical implementation of dynamic serving

In order to implement dynamic serving on your website, their are some key elements you must take into consideration.

Dynamically pre-rendering a JavaScript website and serving it to Google as a static page takes a long time. This can take anything from 5-10 seconds (time to first byte) which will make your website almost uncrawlable for bots.

To solve this, we must introduce a caching layer within out dynamic serving infrastructure. See the diagram below to help illustrate.


Pre-rendered (dynamic serving) pages should be cached. This means that the page has already been built in the background, therefore does not need to be pre-rendered on the fly  when Google requests it, which is very slow.

Cached pages can be served to Google in under 200ms, whereas doing it on the fly will take anything from 5 seconds at best to 10+ seconds.

Note: we have seen large websites lose over 50% of their organic traffic due to pre-rendering on the fly, resulting in Google not being able to access/crawl the website properly. We can’t stress enough how important it is to not do this! Remember, a high time to first byte signals to Google that your servers are unable to handle the traffic, which causes Google to slow down. Imagine a time to first byte that’s 1,000%+ over Google’s recommended 200ms limit!

I will not go into the details of caching and how it all works in the background, however if it is something you are interested in. Please do contact us and if we gain enough interest we can go into comprehensive detail.

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