# fastify-disablecache

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> Fastify plugin to disable client-side caching

## Overview

Inspired by [nocache](https://github.com/helmetjs/nocache), the `fastify-disablecache` plugin sets the following response headers and values to disable client-side caching:

```
Cache-Control: no-store, max-age=0, must-revalidate, proxy-revalidate
Expires: 0
Pragma: no-cache
Surrogate-Control: no-store
```

This plugin was created out of a need for an easy way to disable client-side caching for data received from backend APIs. This ensures data is always current when called by applications.

### Why these headers?

- `Cache-Control` - Primary response header for configuring cache controls [since HTTP/1.1](https://httpwg.org/specs/rfc7234.html#header.cache-control); whilst `no-store` is the directive to disable caching, clients such as [Internet Explorer](https://learn.microsoft.com/en-us/troubleshoot/developer/browsers/connectivity-navigation/how-to-prevent-caching#the-cache-control-header) did not use it, thus the addition of `max-age=0, must-revalidate`; `proxy-revalidate` is added to ensure legacy proxies that only partially implemented support for `must-revalidate` also revalidate the response
- `Expires` - Included for backwards compatibility with [HTTP/1.0 caches](https://www.w3.org/Protocols/HTTP/1.0/spec.html#Expires)
- `Pragma` - Included for backwards compatibility with [HTTP/1.0 caches](https://www.w3.org/Protocols/HTTP/1.0/spec.html#Pragma), is [used by Internet Explorer](https://learn.microsoft.com/en-us/previous-versions/troubleshoot/browsers/connectivity-navigation/how-to-prevent-caching#the-pragma-no-cache-header)
- `Surrogate-Control` - Not a standardised response header but is [used by CDNs and reverse proxies](https://www.w3.org/TR/edge-arch/) for cache control

## Installation

Install using `npm`:

```sh
npm i fastify-disablecache
```

### Compatibility

| Plugin version | Fastify version |
| -------------- | --------------- |
| `>=4.x`        | `^5.x`          |
| `>=3.x <4.x`   | `^4.x`          |
| `>=1.x <3.x`   | `^3.x`          |

Please note that if a Fastify version is out of support, then so are the corresponding versions of this plugin
in the table above.
See [Fastify's LTS policy](https://github.com/fastify/fastify/blob/main/docs/Reference/LTS.md) for more details.

## Example usage

```js
"use strict";

const Fastify = require("fastify");
const disableCache = require("fastify-disablecache");

const server = Fastify();
server.register(disableCache);

server.get("/", (_req, res) => {
	res.send("ok");
});

server.listen(3000, (err) => {
	if (err) throw err;
	console.log("Server listening on 3000");
});
```

## Contributing

Contributions are welcome, and any help is greatly appreciated!

See [the contributing guide](https://github.com/Fdawgs/.github/blob/main/CONTRIBUTING.md) for details on how to get started.
Please adhere to this project's [Code of Conduct](https://github.com/Fdawgs/.github/blob/main/CODE_OF_CONDUCT.md) when contributing.

## Acknowledgements

- [**Aras Abbasi**](https://github.com/uzlopak) - TypeScript support
- [**Evan Hahn**](https://github.com/EvanHahn) - [nocache](https://github.com/helmetjs/nocache) developer
- [**Matteo Collina**](https://github.com/mcollina) - Optimisation suggestions

## License

`fastify-disablecache` is licensed under the [MIT](./LICENSE) license.