# Reusable Step Libraries

Reusable Step Libraries let you define steps once and use them across all projects in your organization.

## How they differ from project steps

**Project steps** are defined in each project's `valohai.yaml`:

* Specific to one project
* Tied to your codebase
* Modified by anyone with project access

**Library steps** are defined in separate Git repositories:

* Shared across your entire organization
* Managed centrally by admins
* Reusable without duplication

## When to use libraries

Create library steps for workflows you run repeatedly across projects:

* Database queries (Redshift, BigQuery, Snowflake)
* Image preprocessing
* Model evaluation scripts
* Docker image builds
* Data validation checks
* Report generation

If you find yourself copying the same step definition into multiple projects, it belongs in a library.

## Two types of libraries

### Valohai Ecosystem Libraries

Pre-built steps maintained by Valohai:

* Database connectors (AWS Redshift, GCP BigQuery, Snowflake)
* Common ML workflows
* Infrastructure utilities (Docker Image Builder)

See [Using Valohai Ecosystem Libraries](https://docs.valohai.com/reusable-step-libraries/ecosystem-libraries) to get started.

### Custom Libraries

Your own reusable steps:

* Organization-specific workflows
* Custom integrations
* Internal tooling

See [Build Your Own Library](https://docs.valohai.com/reusable-step-libraries/build-your-own-library) to create one.

## How it works

1. **Admins** connect Git repositories as libraries
2. **Library YAML** defines steps with metadata (category, icon, description)
3. **All users** see library steps when creating executions
4. **Steps run** just like project steps—same parameters, same environments

Library steps appear in the execution creation UI alongside your project steps, organized by category.

## What makes a good library step?

**Good candidates:**

* Generic and reusable across projects
* Well-documented with clear parameters
* Stable and rarely changes
* Solves a common problem

**Poor candidates:**

* Highly project-specific logic
* Frequently changing implementations
* Tightly coupled to one codebase

## Next steps

**Use existing libraries:** Start with [Valohai Ecosystem Libraries](https://docs.valohai.com/reusable-step-libraries/ecosystem-libraries) for database connectors and common utilities.

**Build your own:** Follow [Build Your Own Library](https://docs.valohai.com/reusable-step-libraries/build-your-own-library) to create custom steps for your organization.