> For the complete documentation index, see [llms.txt](https://docs-29.gitbook.io/usdd-v2/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-29.gitbook.io/usdd-v2/introduction.md).

# INTRODUCTION

- [What is the new version of USDD?](https://docs-29.gitbook.io/usdd-v2/introduction/what-is-the-new-version-of-usdd.md)
- [What is USDDOLD?](https://docs-29.gitbook.io/usdd-v2/introduction/what-is-usddold.md)
- [Why upgrade USDD?](https://docs-29.gitbook.io/usdd-v2/introduction/why-upgrade-usdd.md)
- [Core Features](https://docs-29.gitbook.io/usdd-v2/introduction/core-features.md)
- [Collateral Asset Contract Addresses](https://docs-29.gitbook.io/usdd-v2/introduction/collateral-asset-contract-addresses.md)