By their nature, headless CMSes lack full-fledged editorial experience integrated into the front ends to which they serve content.
Unless they expose a content editing interface tied to each front end, in-context administration and in-place editing are impossible. In other words, to provide an editorial experience on the front end, that front end must be aware of that content editing interface — hence the necessity of coupling.
Display and layout manipulation is another area that is key to making marketers successful. One of Drupal's key features is the ability to control where content appears in a layout structure. Headless CMSes are unopinionated about display and layout settings. But just like in-place editing and in-context administration, editorial tools that enable this need to be integrated into the front end that faces the end user in order to be useful.
In addition, editors and marketers are particularly concerned about how content will look once it's published. Access to an easy end-to-end preview system, especially for unpublished content, is essential to many editors' workflows. In the headless CMS paradigm, developers have to jump through fairly significant hoops to enable seamless preview, including setting up a new API endpoint or staging environment and deploying a separate version of their application that issues requests against new paths. As a result, I believe seamless preview — without having to tap on a developer's shoulder — is still necessary.
Features like in-place editing, in-context administration, layout manipulation, and seamless but faithful preview are essential building blocks for an optimal editorial experience for content creators and marketers. For some use cases, these drawbacks are totally manageable, especially where an application needs little editorial interaction and is more developer-focused. But for content editors, headless CMSes simply don't offer the toolkits they have come to expect; they fall short where Drupal shines.
Drupal empowers both editors and application developers
This diagram illustrates the differences between a coupled — but headless-enabled — Drupal website and a headless CMS with various front ends receiving content.
All of this isn't to say that headless isn't important. Headless is important, but supporting both headless and traditional approaches is one of the biggest advantages of Drupal. After all, content management systems need to serve content beyond editor-focused websites to single-page applications, native applications, and even emerging devices such as wearables, conversational interfaces, and IoT devices.
Fortunately, the ongoing API-first initiative is actively working to advance existing and new web services efforts that make using Drupal as a content service much easier and more optimal for developers. We're working on making developers of these applications more productive, whether through web services that provide a great developer experience like JSON API and GraphQL or through tooling that accelerates headless application development like the Waterwheel ecosystem.
For me, the key takeaway of this discussion is: Drupal is great for both editors and developers. But there are some caveats. For web experiences that need significant focus on the editor or assembler experience, you should use a coupled Drupal front end which gives you the ability to edit and manipulate the front end without involving a developer.
For web experiences where you don't need editors to be involved, Drupal is still ideal. In an API-first approach, Drupal provides for other digital experiences that it can't explicitly support (those that aren't web-based). This keeps both options open to you.
Drupal for your site, headless Drupal for your apps
This diagram illustrates the ideal architecture for Drupal, which should be leveraged as both a front end in and of itself as well as a content service for other front ends.
In this day and age, having all channels served by a single source of truth for content is important. But what architecture is optimal for this approach? While reading this you might have also experienced some déjà-vu from a blog post I wrote last year about how you should decouple Drupal, which is still solid advice nearly a year after I first posted it.
Ultimately, I recommend an architecture where Drupal is simultaneously coupled and decoupled; in short, Drupal shines when it's positioned both for editors and for application developers, because Drupal is great at both roles. In other words, your content repository should also be your public-facing website — a contiguous site with full editorial capabilities. At the same time, it should be the centerpiece for your collection of applications, which don't necessitate editorial tools but do offer your developers the experience they want. Keeping Drupal as a coupled website, while concurrently adding decoupled applications, isn't a limitation; it's an enhancement.
Today's goal isn't to make Drupal API-only, but rather API-first. It doesn't limit you to a coupled approach like CMSes without APIs, and it doesn't limit you to an API-only approach like Contentful and other headless CMSes. To me, that is the most important conclusion to draw from this: Drupal supports an entire spectrum of possibilities. This allows you to make the proper trade-off between optimizing for your editors and marketers, or for your developers, and to shift elsewhere on that spectrum as your needs change.
It's a spectrum that encompasses both extremes of the scenarios that a coupled approach and headless approach represent. You can use Drupal to power a single website as we have for many years. At the same time, you can use Drupal to power a long list of applications beyond a traditional website. In doing so, Drupal can be adjusted up and down along this spectrum according to the requirements of your developers and editors.
In other words, Drupal is API-first, not API-only, and rather than leave editors and marketers behind in favor of developers, it gives everyone what they need in one single package.
Special thanks to Preston So for contributions to this blog post and to Wim Leers, Ted Bowman, Chris Hamper and Matt Grill for their feedback during the writing process.