# Frequently Asked Questions

## What is the Deno Standard Library?

The Deno Standard Library is a library of packages that aim to provide a robust,
secure, and modern foundation for building JavaScript and TypeScript
applications.

## Which APIs does the Standard Library support?

The Standard Library aims to compliment the
[JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference),
[Web](https://developer.mozilla.org/en-US/docs/Web/API) and
[Deno runtime](https://deno.land/api) APIs.

## Which runtimes are compatible with the Standard Library?

By virtue of the APIs it supports, the Standard Library primarily aims to work
with:

1. [Deno](https://deno.com/) (latest stable version and canary)
1. [Deno Deploy](https://deno.com/deploy)
1. Web browsers (i.e. [Google Chrome](https://www.google.com.au/chrome/),
   [Mozilla Firefox](https://www.mozilla.org/firefox/),
   [Apple Safari](https://www.apple.com/safari/), etc.)

Other runtimes are supported to varying degrees, depending on how much they
support the same APIs that the Standard Library targets. These runtimes include:

1. [Node.js](https://nodejs.org/)
1. [Cloudflare Workers](https://workers.cloudflare.com/)
1. [Bun](https://bun.sh/)

## Why is the Standard Library versioned differently to the Deno runtime?

Deno is not the only runtime that the Standard Library is designed to work with
(see above section). Hence, there's no reason to have Deno and the Standard
Library to be versioned the same. Also, having both projects versioned
independently allows them to progress asynchronously.

## Which versions of Deno is the Standard Library guaranteed to work with?

The Standard Library is designed to work with the latest stable and canary
versions of Deno. This is checked-for with all PRs in CI.

## How is the Standard Library distributed?

The Standard Library is distributed as a library of packages on
[JSR](https://jsr.io/), a modern package registry for JavaScript and TypeScript.

To learn more about JSR, see the [documentation](https://jsr.io/docs).

## Which version of a given package should I use?

We recommend using the latest version of a given package.

Thanks to JSR, you can constrain dependency versions by defining the SemVer
range in the import specifier.

E.g. If the latest major version of a package is 1, it should be imported as
follows:

```ts, ignore
import { bar } from "jsr:@std/foo@^1";
```

The same goes if the latest major version of a package is 0:

```ts, ignore
import { bar } from "jsr:@std/foo@^0";
```

This approach allows for bug fixes and new features, while avoiding breaking
changes.

For more information, see JSR's
[SemVer resolution](https://jsr.io/docs/using-packages#semver-resolution)
documentation.

## Why would an API be deprecated?

An API is deprecated due to one of the following reasons:

1. It's been covered by a new JavaScript language or Web Standard API.
1. It's been moved to a more appropriate location. E.g. To another package.
1. It's been renamed more appropriate. E.g. To a name that more clearly
   describes its behavior.
1. It's been deemed no longer fitting to the Standard Library.

## When is a deprecated API removed?

In almost all cases, a deprecated API is removed in the next major version after
deprecation. This is to minimize breaking changes for users.

## Can I still use a deprecated API?

Yes. You can use a package version that contains the deprecated API in question
by pinning the package version.

E.g. Say `bar()` is deprecated in `@std/foo@0` and removed in `@std/foo@1`. Pin
the import specifier to `@std/foo@0` to continued use:

```ts, ignore
import { bar } from "jsr:@std/foo@^0/bar";
```

This is possible thanks to JSR being immutable. For more information, see JSR's
[Immutability](https://jsr.io/docs/immutability) documentation.

## An API I was using is no longer available in the Standard Library. What happened to it?

It's most likely API has been moved, removed or renamed. These changes are
always noted in, and most easily found in the
[release notes](https://github.com/denoland/std/releases). To find how an API's
been modified, search for your API in the **Find a release** search bar.

If you still cannot find the API you're looking for, please
[open an issue](https://github.com/denoland/std/issues/new?assignees=&labels=bug%2C+needs+triage&projects=&template=bug_report.md&title=).

## How can I contribute to the Standard Library?

Check out the contributing guidelines [here](CONTRIBUTING.md).

## How is the Standard Library codebase structured?

Check out the architecture guide [here](ARCHITECTURE.md).
