Developing Blocks

A quick start guide to developing blocks

The quickest start

Any valid HTML is already a block.

Got some HTML? Congratulations, you have a block. Go publish your block so that others can find and use it!

Do you want your block to interact with the application using it? Read on.

Almost-as-quick start

Blocks are web components. We suggest writing them using React, a ready-made framework for writing web components. If you need it, here’s an intro to React.

Blocks can be sent data by the apps using them. Blocks can tell apps what types of data they take. We suggest writing blocks in TypeScript, which helps describe types.

We’ve provided a template to help you get started - here’s how to use it.

We'll be releasing a fully-working, open-source application showing off how to write and use blocks, in January 2022.

If you want to know when the demo application is available, please register your interest.


  1. Run yarn create-block-app yourblockname /path/to/yourblockname
  2. Switch to your new folder: cd /path/to/yourblockname
  3. Run yarn install && yarn dev
  4. Open http://localhost:9090 in your browser. You should see ‘Hello World!’


Edit src/App.tsx to change the behavior of your block.

The AppProps type describes what data your block accepts - the names and types of properties that embedding applications should pass to your block. You can pass in dummy data for testing in webpack-dev-renderer.tsx.

Embedding applications may also pass an updateEntities function, an entityId and an entityTypeId as properties to your block - these are the ids identifying your block data in the app. Call updateEntities with any new data you want the app to set for your block - it should match the data types you have defined in AppProps.

For more about editing data from blocks, read the specification.


Once you’ve finished writing your block, run yarn build.

This will produce a compiled version of your code in the dist folder, along with metadata files describing your block, and the data it accepts (its schema).

You now have a block package that you can provide to apps to use, by publishing it on the Block Hub.

I don’t want to use TypeScript

You can write your block in regular JavaScript using the method described above - just rename your app to App.jsx, remove the types, and get coding - but the block schema will not be automatically generated as part of the build process.

You can write your own block schema manually, giving the type of props your App component accepts in JSON Schema format.

I don’t want to use React

We will be releasing examples of how to write blocks using different frontend libraries in the near future.


Once you've built your block, make sure to publish it on the Block Hub to show it off to the world, and claim your namespace!