---
title: "Extensions"
id: external-extensions
pg_version: "20devel"
---

<a id="external-extensions"></a>

## H.4. Extensions

PostgreSQL is designed to be easily extensible. For this reason, extensions loaded into the database can function just like features that are built in. The `contrib/` directory shipped with the source code contains several extensions, which are described in [Appendix F](contrib.md). Other extensions are developed independently, like [PostGIS](https://postgis.net/). Even PostgreSQL replication solutions can be developed externally. For example,  [Slony-I](https://www.slony.info) is a popular primary/standby replication solution that is developed independently from the core project.