The open-source protocol for creating interactive, data-driven blocks
This document is a working draft
This specification is currently in progress. We’re drafting it in public to gather feedback and improve the final document. If you have any suggestions or improvements you would like to add, or questions you would like to ask, feel free to submit a PR or open a discussion on our GitHub repo.
The Block Protocol specifies how developers can define web "blocks" – discrete components displayed on a web page or other application – and how such blocks communicate with any application embedding them.
It defines how structured data is passed between blocks and embedding applications, enabling any protocol-compliant application to use any protocol-compliant block to make structured data viewable and editable by users.
What’s a specification?
A specification is a document that outlines how a system should be built. They help make applications and websites interoperable.
The Block Protocol is split into a core specification and service specifications.
The core specification sets out how blocks should be defined, how services are defined, how embedding applications should initialize blocks, and how applications and blocks communicate.
Each service specification defines what applications and blocks communicate. A service is a logical grouping of messages blocks and applications may exchange.
Each specification is versioned separately, allowing them to evolve independently. Any reference to the ‘protocol version’ should be read as the version of the core specification.
Separate core and service specifications were introduced in version 0.2 of the Block Protocol.
A quick note
This section provides narrative and guidance to aid the reader in understanding the context and motivation for the Block Protocol. It does not form part of the specification.
Many modern content creation systems, such as WordPress and Notion, use a concept of ‘blocks’ to build content pages from. Users typically click on a big + button which allows them to insert one of any number of blocks of different types (e.g. paragraph, list, table, video). Pages built in this modular fashion can be as varied and interactive as the repertoire of available blocks. But these block systems are generally closed ecosystems. It is either (a) impossible for users to create new block types, or (b) impossible to use any block types created in one of these applications in another.
Even outside of content creation systems, web developers make use of a wide range of software libraries which implement web blocks: libraries to display, select, or edit particular types of data. These all have their own definition of what data they accept, how to send data into them, and how they send data back out. Making use of these libraries often requires learning a specific data interface and its idiosyncrasies.
This protocol aims to address both problems by defining a contract for data transfer between blocks and the applications which wish to make use of them, and how blocks describe the data they accept. If you adopt this protocol:
The protocol enables this by specifying:
Given a catalog of blocks built in compliance with the protocol, and embedding applications which know how to use them – which we can provide abstractions for – users can more easily find and use blocks to display and edit data structures they are interested in, be that tasks, tweets, or anything else.
A user could take a data structure, and search for blocks which can handle that data structure (or a useful portion of it) – whether they are a developer wanting to bundle a block with an application, or an end user of an embedding application which allows users to find and add new blocks themselves.
Blocks are as customizable as any other current component allows, but with a strong default setup, theme, and a predictable interface governed by this protocol, that provides plug-and-play functionality for data.
Anyone with an existing application who wants to embed semantically-rich, reusable blocks in their product can use the protocol. Improve your app’s utility and tap into a world of structured data with no extra effort, for free.