> For the complete documentation index, see [llms.txt](https://docs.substreams.dev/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.substreams.dev/readme.md).

# Introduction

Substreams is a powerful indexing technology, which allows you to:

* Extract data from several blockchains (Solana, Ethereum, Polygon, BNB...).
* Apply custom transformations to the data.
* Send the data to a place of your choice (for example, a Postgres database or a file).

<figure><img src="/files/iMDcDHQ7ztHaklNn0UCA" alt="" width="100%"><figcaption></figcaption></figure>

**You can use Substreams packages to define which specific data you want to extract from the blockchain**. For example, consider that you want to retrieve data from the Uniswap v3 smart contract. You can simply use the [Uniswap v3 Substreams Package](https://substreams.dev/packages/uniswap-v3/v0.2.10) and send that data wherever you want!

### How Does It Work?

Watch the following video and visit the [Getting Started](/getting-started.md) to learn more about how Substreams works.

{% embed url="<https://www.youtube.com/watch?v=gVqGCqKVM08>" %}
Get an overview of Substreams
{% endembed %}