Build your first Block

Create and import a tested JavaScript Block in a few commands.

Prerequisites

Download and extract the SDK 0.1.0. Install Node.js 22 or later. Run commands from the extracted SDK folder. The runtime and its dependencies are bundled; the following example needs no account, API key, npm install, or network request.

Create a Block

node packages/block-cli/cli.js create ./my-block javascript

The scaffold creates these editable files:

my-block/
  stillmade.block.json
  src/run.js
  tests/fixtures.json

Understand the source

The manifest declares the contract. The source is a synchronous function body receiving validated inputs through input:

const text = input.text.trim();
return { text, words: text ? text.split(/\s+/).length : 0 };

The exact input/output names come from the manifest. There is no server to configure and no hidden credential to supply.

Validate and test

node packages/block-cli/cli.js validate ./my-block
node packages/block-cli/cli.js test ./my-block
node packages/block-cli/cli.js preview ./my-block

Validation checks package structure. Tests execute every fixture through the isolated runtime and compare the entire returned output with its expected value. Preview executes the first fixture and prints its outputs. A failed test must be corrected before packaging.

Import the finished folder

Open Create import, choose Choose folder, and select my-block. Its manifest, implementation, fixtures and optional src/view.html, src/view.css, src/view.js interface load unchanged. Review checks and the actual preview, then confirm import after the required source-rights and device review. The SDK contracts are the foundation from the first development step; there is no source adaptation phase.

Package an alternate delivery file

For an original implementation, retain complete license notices and at least two fixtures (normal and edge cases), then run:

node packages/block-cli/cli.js pack ./my-block ./my-block.stillmade-block --original

Select that file with Choose package for the same source and interface. Packaging adds retained source evidence and reruns applicable checks; it does not rewrite the implementation. Output files are never silently overwritten. Use repository evidence instead of --original when reusing third-party code.

Photo-editor folder example

The extracted SDK contains examples/original-photo-editor/, including its actual custom interface, pixel processing and fixtures. Select that folder directly or try its packaged original. This bounded example adjusts brightness/color and rotates pixels with transparency. See the supported original-authoring contract.

Use and iterate

Add the Block to a Project Type, configure its inputs, and run it. Keep source changes in checkpoints; publish a new release version when the behavior changes. See versioning and remixing.