Headless CMS: What is a headless CMS?

What is a headless CMS?

A headless CMS is a content management system that radically separates the editorial back-end (where content is created, organised and stored) from the display front-end (where content is made visible to users). Communication between the two occurs exclusively via an API, typically REST or GraphQL. The term "headless" refers to the absence of an integrated presentation layer: the CMS provides raw content, and it is up to the front-end developer to choose how and where to display it.

This architecture contrasts with the traditional (or "monolithic") CMS, such as WordPress in its standard configuration, where the editorial back-end and display front-end are tightly coupled within the same system. In a monolithic CMS, display templates are managed by the CMS itself.

At Kern-IT, we work with Wagtail CMS, a Django-based CMS that offers the best of both worlds: it can operate in traditional mode with Django templates served on the server side, but it also has a complete REST API that enables headless operation. This flexibility allows Kern-IT to choose the architecture best suited to each project.

Why headless CMS matters

The headless approach responds to the evolution of the digital landscape, where content must be distributed across a multitude of channels and devices.

• Multichannel distribution: the same content can feed a website, a mobile application, an interactive kiosk, a voice assistant or a connected display. Content is created once and distributed everywhere via the API.
• Front-end technology freedom: front-end developers can choose the most suitable technology (React, Vue.js, Next.js, Nuxt, or even Django templates with Tailwind CSS) without being constrained by the CMS.
• Performance: by decoupling front-end from back-end, modern techniques (static generation, edge CDN, server-side rendering) can be used to significantly improve load times.
• Security: the CMS is not directly exposed to site visitors. Only the API is accessible, reducing the attack surface.
• Independent scalability: the editorial back-end and front-end can be scaled independently according to each one's needs.

Traditional, headless and hybrid CMS

It is important to understand the three available architectures to make an informed choice.

The traditional CMS (monolithic) manages content and its display within a single system. It is the simplest approach to implement and the most suitable for projects where only one web channel is needed. Content is created in the admin and displayed via templates integrated into the CMS.

A pure headless CMS provides only the editorial back-end and an API. It offers no rendering capability. The front-end is entirely external. CMSs like Contentful, Strapi or Sanity follow this approach. The advantage is total flexibility; the drawback is increased architectural complexity and the inability for content editors to preview their work.

A hybrid CMS (or "decoupled-capable") offers both traditional rendering capabilities and an API for headless mode. Wagtail CMS is an excellent example of a hybrid CMS: it provides a powerful Django template system for server-side rendering, an admin interface with real-time preview and a complete REST API for distributing content to other channels. At Kern-IT, this flexibility allows us to deploy Wagtail in traditional mode for showcase sites and in headless mode when the project demands it.

Concrete example

Kern-IT is designing the digital platform for a Brussels museum chain. Content (artwork descriptions, opening hours, events, tickets) must be distributed across four channels: the website, a visitor mobile app, interactive kiosks in exhibition halls and information screens in entrance halls.

The chosen solution is Wagtail CMS in hybrid mode. The main website uses Django templates with Tailwind CSS, benefiting from performant server-side rendering and real-time preview for content editors. The mobile app and interactive kiosks consume content via Wagtail's REST API. The information screens use a lightweight front-end querying the same API.

The museum's editorial team manages all content in a single Wagtail admin interface. When they update an exhibition's opening hours, the change is instantly reflected across all four channels. This approach eliminates content duplication and inconsistency risks.

Implementation steps

1. Assess distribution channels: inventory current and future channels that will need to consume content (website, mobile app, kiosks, partner APIs).
2. Choose the architecture: if only one web channel is needed, the traditional approach is often sufficient and simpler. If multiple channels are planned, a headless or hybrid approach is warranted.
3. Select the CMS: favour a hybrid CMS like Wagtail that offers the flexibility to switch between modes without changing platforms.
4. Structure the content: define content models and relationships between content types in a channel-agnostic manner.
5. Design the API: configure the REST or GraphQL API with the necessary endpoints, authentication and appropriate permissions.
6. Develop the front-ends: create the interfaces for each channel by consuming the CMS API.
7. Preview: set up a preview system so editors can see how their content will render before publishing.

Related technologies and tools

• Wagtail CMS: the Django-based hybrid CMS used by Kern-IT, offering a native REST API, an admin interface with preview and traditional rendering capabilities via Django templates.
• Django REST Framework: the framework powering Wagtail's REST API, providing advanced serialisation, authentication and filtering capabilities.
• Tailwind CSS: the CSS framework used for the main website front-end, whether in traditional mode (Django templates) or headless mode (separate front-end application).
• GraphQL (Wagtail-grapple): a Wagtail extension adding GraphQL support for front-end clients that prefer this approach over REST.

Conclusion

A headless CMS is a powerful architecture for multichannel projects, but it is not a universal solution. A hybrid CMS like Wagtail offers the best balance: the simplicity and performance of traditional server-side rendering when a single web channel suffices, and the flexibility of a complete API when content must be distributed across multiple channels. At Kern-IT, the KERNWEB division leverages this duality of Wagtail to deliver solutions tailored to each client's exact needs, without over-engineering simple projects or underestimating complex ones.