Nathan Wrigley talks with Seth Rubenstein, head engineer at Pew Research Center, about how block composability is reshaping WordPress and the block editor. Seth leads Pew’s WordPress platform team and contributes to Gutenberg, focusing on open source work that benefits the broader community.
What is composability
Seth defines composability as building modular, reusable pieces that can be assembled into richer web experiences—like React components but inside the block editor. Gutenberg has evolved from static content blocks (paragraphs, images) to blocks that perform actions and communicate with each other. That transformation makes it possible to create interactive features—quizzes, calculators, pivot tables—directly in the editor without separate custom front ends.
Pew’s Quiz Builder example
Pew built a Quiz Builder using a quiz post type and nested blocks: a quiz controller, question blocks, and answer blocks. Answers can include text, images, charts, videos, or other interactive elements. Blocks adapt based on context: adding a scoring block, for instance, can change scoring behavior without overwriting core functionality. The authoring experience stays simple and drag-and-drop for editors.
Three key API developments
1) Block Bindings API
– Lets developers bind block attributes to programmatic sources so core blocks can be reused instead of creating many custom blocks. For example, Pew binds a core paragraph’s content attribute to an answer block, using the paragraph for layout while supplying content programmatically.
– This reduces custom block count, minimizes interface clutter, and makes blocks more extensible and approachable for editors.
– Documentation and tutorials are available and the API is approachable for developers.
2) Block Bits (concept / in development)
– A finer-grained idea to bind or swap small parts inside a block’s content, down to words or characters. Use cases include templating a single line with dynamic pieces like names, ISBNs, currency symbols, or links inserted inside text.
– Block Bits would let a line contain dynamic metadata rather than forcing multiple separate blocks for each piece.
– Still conceptual and dependent on HTML API improvements, but experiments are possible today using rich text custom formats and the HTML Tag Processor to replace class-marked spans with dynamic content.
3) Interactivity API
– A WordPress-native Preact-based framework that lets blocks run JavaScript on the front end and share state. It enables atomic, composable interactions: nested blocks can alter submit handlers, hoist state into a shared model, and connect behaviors declaratively.
– Pew rewrote Quiz Builder to use Interactivity, moving scoring and interactivity client-side and eliminating duplicated React front ends and server-side processing. The result is better performance and less server work.
– Interactivity supports prefetching and caching. Query loop pagination, for example, can prefetch next pages on hover so clicks feel instantaneous.
HTML Tag Processor and performance
The HTML Tag Processor efficiently processes HTML and swaps dynamic pieces at scale, outperforming older PHP DOM approaches. Combined with Interactivity (Preact), these tools often yield better performance than separate React front ends by reducing server load, enabling client-side state, and supporting prefetch/caching strategies for heavy datasets.
Developer and editor tooling
Right now these capabilities are primarily developer APIs. Developers build the tools and UIs that expose them to editors. Panels already exist for some features: Block Bindings surfaces attribute selection, and Pew built an Interactivity panel to visualize allowable connections. There is a clear opportunity for plugin authors to build higher-level UIs—similar to Advanced Custom Fields—that make bindings, bits, and interactions configurable by non-developers. Automattic’s Remote Data Blocks is an early example that maps remote data sources into blocks and bindings with an editor-friendly UI.
Missing pieces and future work
A major gap is responsive or device-contextual attributes. Developers need consistent patterns and tooling so block attributes can change by viewport (desktop, tablet, mobile). Examples include responsive column layouts that reflow differently across breakpoints or buttons that trigger native sharing on mobile but a different action on desktop. The APIs exist in parts, but cohesive guidance and finished tooling for device-aware attributes are still needed.
Broader perspective and call to experiment
WordPress is moving toward a block-native web application platform. Creators can build interactive, data-driven apps inside the editor by composing blocks. For plugin authors and developers there is a big opportunity to build UIs and templates that hide complexity and let editors use these features via simple drag-and-drop tools. Seth encourages experimentation and contributions to refine these APIs and tooling.
Where to find Seth
Seth is at sethrubenstein.info and active on social platforms (Twitter, Bluesky). He invites people to reach out, experiment with the APIs, and contribute.
Conclusion
The promise of Gutenberg is maturing: interactive web apps inside the block editor are becoming practical. Developers should explore Block Bindings, the Block Bits concept, the Interactivity API, and related tools to help shape the next phase of WordPress and make composable, interactive experiences accessible to editors.
