> For the complete documentation index, see [llms.txt](https://davidjosearaujo.gitbook.io/online-courses/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://davidjosearaujo.gitbook.io/online-courses/blockchain-security/beyond-the-basics/alternative-distributed-ledger-architectures/introduction-to-sidechains.md).

# Introduction to sidechains

**Sidechains are blockchains that are "pegged" to another blockchain.** This allows users of the main chain **to transfer their tokens to the sidechain and back again**

To send tokens to a sidechain, a user sends them to an output address where they are locked. After a suitable delay,  the corresponding amount of tokens are released on the sidechain

The user can perform transactions on the sidechain and then transfer back to the main chain when they wish