With headless CMS architecture comes freedom of how to render content for the user, and the two most commonly used rendering methods are Static Site Generation (SSG) and Server-Side Rendering (SSR). Each rendering approach comes with advantages and disadvantages that impact a digital experience’s performance, scalability, and flexibility. The best rendering solution depends on a variety of considerations, including how often content will change, expected traffic and engagement patterns, personalization needs, and infrastructure intentions. It’s important to understand both how SSG and SSR operate independently from headless CMS solutions and in conjunction with them to create fast, dependable digital experiences that stand the test of time. This blog post outlines the differences between SSG and SSR, and the pros and cons of each rendering method relative to headless deployments.
H2: Static Site Generation- What It Means in a Headless World
Static Site Generation (SSG) involves pre-rendering pages at build time to be served as static HTML files through a CDN. SSG in a headless environment involves compiling content from a CMS at build time to create static pages to be distributed across the globe. Management API access is essential in this process, as it allows build pipelines to programmatically fetch, structure, and update content during each build cycle. It’s super performant because, upon requesting a page, there is no need for server computation everything is already rendered and cached, loadable immediately. Thus, SSG works best for sites with stable content or consistent expected changes, like blogs, documentation, marketing sites, or landing pages. SSG reduces load times, increases scalability and avoids excess hosting costs due to fewer dependencies on a server.
Server Side Rendering- What It Means in a Headless World
Server-Side Rendering (SSR) is the opposite; pages are rendered on the fly at every request. Instead of pre-compiling HTML files at a designated time, HTML is computed at the server based on fresh options from the headless CMS or other data source – every time. With SSR, users load HTML based on the latest version of a page at request time. While this means additional computation for every request – which creates additional overhead on a server with potential performance penalties – it also allows for the most dynamic applications that rely on frequent changes, personalization, user-based content, and real-time data. SSR will offer the latest page every time it’s loaded but comes at a performance cost. However, when rendering at the edge or proper SSL cache rules are in play, SSR becomes incredibly performant and useful in a headless deployment.
Performance Benefits of SSG for Headless CMS Workflows
SSG benefits performance more significantly than SSR in a headless CMS environment for many reasons. SSG serves static files from CDN which means latency is almost non-existent and page loading happens almost immediately regardless of where the user is located. This creates great Core Web Vitals scores, especially LCP and FID; SSG also allows for extreme caching, meaning there’s no additional strain on the system regardless of traffic spikes because there is nothing that needs to render at request time. In fact, SSG reduces infrastructure costs and avoids bottlenecks due to server rendering because there is no need to render anything in real-time on the back end. For projects that work best when content does not need to change frequently or dynamically, SSG is usually best from a performance perspective.
Where SSR Is Better: Real-Time and Dynamic Rendering
While SSG is faster, SSR is better when information must change frequently or be different per user. Real-time applications – e-commerce sites, reservation systems, dashboards, or any personalized application – are best made via SSR. SSR renders based on context, permissions, personalizations and real-time information before rendering the site. Static sites cannot easily render differently for every viewer; with a headless CMS, SSR can ensure the rendered information is up to date without waiting for a full rebuild. SSR takes more resources from the server, but for real-time applications or data-heavy applications, SSR is the only option that makes sense, as it can allow for instantaneous change.
What Trade-Offs Exist with SSG and SSR Related to Scale and Change?
The choice between SSG and SSR often revolves around change versus traffic expectations. Since static files can serve millions upon millions of users without taxing a server, SSG is scalable beyond measure. However, SSG sites must rebuild more often when changes are made – this could come at a snail’s pace if there are many files and content changes on a single large site. Incremental Static Regeneration (ISR) and other tools have been created to combat this necessity. Alternatively, if a site is made via SSR, it must scale backend resources to accommodate more traffic as necessary; however, this is an extra layer of infrastructure planning. While SSG cannot bend to accommodate change at scale, SSR welcomes it while simultaneously requiring additional backing resources. This is a trade-off worth considering for long-term goals.
How Hybrid Rendering Takes the Best of Both Worlds
Modern rendering frameworks like Next.js, Nuxt, SvelteKit and Remix boast hybrid rendering models that allow for both SSG and SSR. Therefore, teams can determine which page/route needs either static pre-rendering or dynamic access via rendering. Any static page that does not need rendering can easily be pre-rendered, while any dynamic page can rely on SSR for personalization and real-time updates. Hybrid rendering is the ultimate flexibility in a headless deployment because teams can choose performance and speed without sacrificing usability. Therefore, it’s easy to have a web experience load instantly via static information while simultaneously tailoring what they experience based on dynamic factors. Hybrid rendering is quickly becoming the go-to method in a headless world because it’s a two-for-one special.
Core Web Vitals Implications on SSG vs SSR
Google’s Core Web Vitals represents another major consideration for determining SSG vs SSR. Generally, LCP, CLS, and FID score best with SSG because static pages render quickly, reliably, and with zero or minimal layout shifts. With SSR, however, this is not always the case as it can also render in a top-tier fashion but it must be optimized to limit TTFB associated with slower backend response times. Fortunately, edge rendering, caching, and prefetching can often get SSRs on par with if not surpass static renderings. Ultimately, both forms of rendering can accomplish good Core Web Vitals when in conjunction with proper strategies and a clean headless architecture.
Developer Experience and Build Times
Developer experience should also be factored into an SSG versus SSR decision. SSG can have long build times for larger sites and it’s critical to implement strategies to paginate, lazily build or on-demand only regenerate what needs to be generated. Yet with SSG, the output is more straightforward and easier to implement. SSR requires more maintenance on the backend, overseeing infrastructure and caching needs but it also renders content in real-time without ever having to go back and rebuild. In headless CMS environments, it’s common for projects to blend both for different teams based on their needs and their update cycles and project scopes. While the need for the ultimate best rendering option must consider developer efficiency amongst the rendering experience, inevitable trade-offs will be made based on future performance and scalability considerations.
Conclusion: A Final Decision for Your Headless CMS
Ultimately the choice between SSG and SSR comes down to project needs. SSG is best for less frequently changing material with performance-demanding requirements or globalized implementations that need the reach of a CDN. Conversely, SSR works best for applications needing dynamic behavior and personalization alongside faster updated content rendering opportunities. With a blend of hybrid rendering, organizations can champion one or the other then adjust their architecture over time as needed. A headless CMS provides flexible APIs for such instances where either approach – or blend – of approaches render content effectively and with an eye on performance and user expectations and needs. There is no losing option as both SSG and SSR play a valuable part in the future of headless architecture.
Edge Rendering for SSG and SSR Workflows in the Headless CMS World
Edge rendering is an application middleware best between SSG and SSR as it provides edge-based rendering logic for the end-user. For SSG, this edge-based network creates static assets to all corners of the globe – response times are so minimal it seems as if the distance between the server and end-user is nonexistent. For SSR, edge functions render pieces of the logic at the edge rather than one central render that holds it all and brings it in, increasing Time to First Byte (TTFB) with added interactivity because things that would otherwise have to load if it were 100% a dynamically rendered page are so quick that they seem, instead, dynamic. For a headless CMS, this edge-rendering renders semantically opposite as it avoids the static versus dynamic thanks to a separated developed architecture that runs faster without losing the integrity of real-time renderings.
Content Freshness for SSG and SSR Systems
Content freshness is one of the biggest make it or break it features of building between SSG and SSR. SSG pages require a build process and need to be rebuilt if they want to change or pull newer information. Essentially, it should be part of the process that whenever information changes, the static portions shift via automatic rebuild to trigger push down. Static build push downs can take time or rely on other types of frameworks like Incremental Static Regeneration (ISR) to bring things fast. For SSR, information is fetched per request so everyone gets the latest version. However, this creates stress for the server as constantly fetching for requests eats up CPU resources and RAM. In the world of headless CMS, freshness is whatever freshness needs to be therefore this either needs to be supported by the system at hand or integrated with everything else to ensure there is a happy medium without bogging things down or lagging things up front.
Cost Factors for Scaling SSG and SSR
Cost is always a factor when dealing with Static Site Generation vs. Server-Side Rendering and scaling with either of them means different potential views from the component side. For SSG, it’s easily ten times less expensive due to a static file being ten times less attractive than rendering requests from a server/edge infrastructure. Static files are easily hosted, easily distributed via CDNs with little to no added cost. There are zero computational costs per request since a build only needs to happen once – or maybe twice or three times if errors arise – for unlimited traffic on the front end. However, with SSR, there are computational costs on a continuous basis as the server/edge needs to render on the fly and dynamically bring files together per every single request. While this gets easier with cloud-based, auto-scaling, serverless (edge deployed) options, it forces companies to consider caps on execution and associated costs for every single rendered page with peak traffic through this scaling equation of either definition. Sometimes, scaling something successful is due to avoiding technical debt for financial cost; sometimes scaling something successful allows for idealized technical solutions with future funding out of mind.
Future Trends in Rendering for Headless CMS Architectures
The rendering approach continues to shift as digital experiences become more complicated and expectations rise. The future of headless, presumably, does not stop at SSG, SSR, and edge-first but instead, combines all three into hybrid systems. Tools yet to be fully realized, like distributed serverless rendering, real-time streaming SSR and AI-based prefetching, stretch the limits of rendering possibilities while frameworks increasingly favor mixed approaches – partial hydration, island architecture, edge-native rendering – and efficiency. As this trend grows, companies should leverage a flexible headless CMS to accommodate ever-changing rendering accommodations and their own requirements as there may not be one solution for the future of headless but rather, the best-rendering solution for each digital experience through an effective combination.
