Server-side rendering (SSR) is a method of loading your website’s JavaScript on your own server. When human users or search engine web crawlers like Googlebot request a page, the content reads as a static HTML page.

Historically, search engines have had difficulty crawling and indexing websites made using JavaScript rather than HTML.

Google indexes JavaScript-based web pages using a two-wave indexing system. When Googlebot first encounters your website, it crawls your pages and extracts all of their HTML, CSS and links, typically within a few hours..

Google then puts the JavaScript content in a queue, rendering it when it has the resources. Sometimes that takes days or weeks. During that time, your web pages are not being indexed and, therefore, not being found on Google. That’s a lot of traffic you’re missing out on. 

What’s worse, if your JavaScript pages aren’t able to be crawled and indexed properly, Google reads them as a blank screen and ranks it accordingly, which can be catastrophic to your website’s SEO health.

Google has claimed that Googlebot is able to crawl and index Javascript-based web pages just fine, but this has yet to be proven. Other search engines such as Bing, Yandex and DuckDuckGo cannot crawl JavaScript at all.

Regardless of the search engine, JavaScript presents a problem because it needs additional processing power to crawl and index, thereby eating up more of your website’s allotted crawl budget.

SSR is designed for this problem. It renders JavaScript on your own servers rather than putting the burden on the user agent, making the content fast and easily accessible when requested.