Block Protocol

The Block Protocol is an open standard which standardizes the means by which blocks and applications are able to communicate, so that any block can be embedded in any application, without either one possessing any special knowledge about the other.

The Block Protocol consists of a Core specification, and various optional modules, each with their own additional specifications. You can learn about these in full by reading the Block Protocol documentation and Block Protocol specification.

Blocks built in accordance with the Block Protocol are also made available on the Block Protocol Hub.

A high-level summary of the Block Protocol is provided below.

Target Audience

The Block Protocol was designed to be understood by two different audiences:

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   Potential block developers who wish to build interoperable, cross-application blocks

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   Potential embedding application developers who wish to build block-based ‘embedding applications’ that leverage the Block Protocol.

While end-users of block-embedding applications may interface with Block Protocol blocks, they are not required or expected to understand its technical implementation or even be aware of its existence.

Architectural Overview

Block Protocol Core

The Block Protocol Core specification outlines what constitutes a block publishable to the Block Protocol Hub. At minimum, a publishable block combines:

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  some source code; and

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  a block metadata file (which can be used to identify a block by potential embedding applications).

The combination of these two things is called a block package, and it is these that can be submitted for listing on the Block Protocol Hub, for download and use by others as blocks.

Block Protocol Modules

While the Block Protocol Core specifies how a block is defined, and how it communicates with an embedding application, modules define what kinds of things blocks and applications can communicate about.

Modules provide logical groups of functionality or aim to solve a specific problem related to block-application interaction. Modules are defined in their own specifications that live separate to, but alongside, the Block Protocol Core.

Most blocks will want to use one or more modules defined as part of the Block Protocol specification.

For example:

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  the Graph module defines the protocol by which blocks can create, read, update or delete entities -- as well as any links between those entities -- within an embedding application’s datastore;

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  the Hook module defines a protocol via which embedding applications can take over specific parts of a block to insert a native application experience, if one exists (e.g. a file picker, or photo gallery);

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  the Service module provides a standardized capability for blocks to interact with external APIs, without needing to ship with their own API keys or prompt users to insert their own.

There are many different types of modules under discussion for inclusion in the Block Protocol, which are described alongside the specification.

In their metadata, blocks can declare which modules (and which version of those modules) they support.

Not all embedding applications will support all modules. For example:

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  New modules are likely to be added on a regular basis, and embedding application developers will require time to build in support for them within their applications.

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  Application developers may have limited bandwidth, and elect to support modules in an incremental manner - prioritizing support for some modules before others.

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  Application developers may never intend to support certain modules, disagreeing with their approach to solving a problem, or because the module is related to functionality which is irrelevant to or unwanted by the application.

In any case, embedding applications can filter the blocks on the Block Protocol Hub to ensure only those blocks requiring modules that their application supports are shown. This allows application creators (and sometimes their users, depending on how the Block Protocol has been integrated) to search, embed and use blocks that are guaranteed to work out-the-box, extending the functionality of embedding applications beyond their original purposes.

HASH supports all of the published Block Protocol modules, and lets you access and use any block published on the Block Protocol Hub.