Aspects Overview

Bit is built entirely with Bit. This means that even Bit itself is built in a component-driven architecture. It uses Harmony which is a component-driven plugin system. Harmony's most fundamental type is an Aspect. Every Aspect is a full-stack feature, capable of extending UI, backend

and any other defined runtime environment. Every Aspect also acts as a service to all others, and its API can be used from any other aspect.

We use Harmony as a way to scale development of dev experiences. We dogfood our own APIs and make Bit extensible for others.


Harmony is a component-based framework for composing extensible applications. Bit uses Harmony to compose itself from components. Every Aspect is a component in Bit, implementing a "feature" that provides an API, and every Aspect can depend on other Aspects and compose them into a new feature.

API first

API is the most primitive interface for a Feature. Therefore, every feature built into Bit is API first and the most fundamental interface for interacting with a Bit Aspect is the programmatic API. Programmatic APIs can be used to compose CLI commands, UI interfaces, GraphQL APIs and RESTful APIs and more, possibilities are endless. Aspect consumers can use the API to extend existing features and build new ones on top of them.

Here is an example to a simple Logger aspect, exposing an API for logging messages and persisting them in memory.

export class MyLoggerAspect {
  private logs = [];

  public log(log: string) {
    console.log('log something');

  public listLogs() {
    return this.logs;

  static async provider() {
    return MyLoggerAspect();

Other aspects can add this aspect as a dependency and use to log messages.

export class MyOtherAspect {
  static dependencies = [MyLoggerFeature];
  static async provider([logger]: [MyLoggerFeature]) {
    logger.log('my cool log message');
    return new MyOtherAspect();


Aspects are extensible by design. Every aspect can expose an API for other aspects to use in order to extend it using Integration Slots. Slot allow other Aspects to "register" a new object that can be later used by them.

An example is the Bit CLI aspects, which other aspects use to add commands. CLI aspect exposes an API for registering new commands, cli.registerCommand() which allows other Aspects to register a new command to Bit.

import { CLIAspect, CLIMain } from '@teambit/cli';

export class MyOtherAspect {
  static dependencies = [CLIAspect];
  static async provider([cli]: [CLIMain]) {
    cli.registerCommand(new MyCommand());
    return new MyOtherAspect();

This allows every aspect to extend the CLI aspect by registering a new command to it. Learn more about Slots.


As mentioned, Bit is built entirely from Aspects and other has been developed by the Bit community, therefore they can be discovered and used in like any other component.

Aspects can be searched and found across


Dogfooding is a core princple of component-driven design, and dev tools development in general. It leans on the philosophy that in order to achieve dev experiences other can enjoy, you must be able to enjoy this yourself. API and feature dogfooding is the key towards generating great dev experiences. Since every Aspect is using itself first, composing its API to various user interfaces, it is been dogfooded by its maintainer.


Aspects can declare and extend different runtime environments. An example could be a Logger Aspect which provides an API, but also extends the UI runtime, adding a logger UI and providing various CLI commands to interact with logs.

Learn more about Runtimes.


Every Aspect be declare a configuration it accepts, and use it for various needs. This allows Aspects to be configured with different configuration on the composition level.

  "my-org.scope/logger": {
    "verbose": true

Learn more about Aspect configuration.