# What changed in fastify-plugin

> 7 changes in fastify-plugin 5 to 6 from its official release notes, upgrade guides and advisories: 3 breaking. Each one cited. Sources checked 2026-10-27. HTML: https://unstale.sh/npm/fastify-plugin/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## fastify-plugin 6

### Breaking changes

- The options object is no longer mutated. (6.0.1) — [release notes](https://github.com/fastify/fastify-plugin/releases/tag/v6.0.1)
- A deprecated interface was removed; TypeScript consumers relying on it may need to update their code. (6.0.0) — [release notes](https://github.com/fastify/fastify-plugin/releases/tag/v6.0.0)

### Behavior and default changes

- The options.name value is now type-checked. (6.0.1) — [release notes](https://github.com/fastify/fastify-plugin/releases/tag/v6.0.1)

### Fixes and other changes

- Hyphenated anonymous plugin names are now preserved. (6.0.1) — [release notes](https://github.com/fastify/fastify-plugin/releases/tag/v6.0.1)
- Passing a nullish plugin now throws the intended TypeError. (6.0.1) — [release notes](https://github.com/fastify/fastify-plugin/releases/tag/v6.0.1)

## fastify-plugin 5

### Breaking changes

- The minimum supported Fastify version was updated. (5.0.0) — [release notes](https://github.com/fastify/fastify-plugin/releases/tag/v5.0.0)

### Behavior and default changes

- The package explicitly declares its JavaScript module type, which affects how Node.js interprets its files. (5.0.0) — [release notes](https://github.com/fastify/fastify-plugin/releases/tag/v5.0.0)