Deno standard library
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A collection of APIs to provide help with asynchronous tasks like delays, debouncing, deferreds or pooling.


Provides helper functions to manipulate Uint8Array byte slices that are not included on the Uint8Array prototype.


This module includes pure functions for specific common tasks around collection types like Array and Record.


Utilities for dealing with Date objects.


Configure environmental variables using .env files.


CLI flag parser.


fs module is made to provide helpers to manipulate the filesystem.


This module is browser compatible.


HTTP server implementation and other utilities for working with cookies and status codes.


Buffering and various utilities for working with Deno's Reader and Writer interfaces.


Logging library with the support for terminal and file outputs. Provides interfaces for building custom loggers.


Provides utility functions for media types.


Utilities for working with OS-specific file paths.


Helpers for interacting with Deno's permissions system.


High level API for dealing with OS signals.


Utilities for working with the Streams API. Includes buffering and conversion.


A reader for dealing with text based protocols like HTTP.


Generators and validators for UUIDs for versions 1, 4 and 5.


Deno Standard Modules


These modules do not have external dependencies and they are reviewed by the Deno core team. The intention is to have a standard set of high quality code that all Deno projects can use fearlessly.

Contributions are welcome!


Standard library is currently tagged independently of Deno version. This will change once the library is stabilized.

To check compatibility of different version of standard library with Deno CLI see this list.

How to use

These modules will eventually be tagged in accordance with Deno releases but as of today we do not yet consider them stable and so we version the standard modules differently from the Deno runtime to reflect this.

It is strongly recommended that you link to tagged releases to avoid unintended updates and breaking changes.

Don't link to / import any module whose path:

  • Has a name or parent with an underscore prefix: _foo.ts, _util/bar.ts.
  • Is that of a test module or test data: test.ts, foo_test.ts, testdata/bar.txt.

Don't import any symbol with an underscore prefix: export function _baz() {}.

These elements are not considered part of the public API, thus no stability is guaranteed for them.


To browse documentation for modules:


NOTE: This repository was unarchived and synced on Feb, 1st, 2021. If you already had it cloned, we suggest to do a fresh clone to avoid git conflicts.

deno_std is a loose port of Go's standard library. When in doubt, simply port Go's source code, documentation, and tests. There are many times when the nature of JavaScript, TypeScript, or Deno itself justifies diverging from Go, but if possible we want to leverage the energy that went into building Go. We generally welcome direct ports of Go's code.

Please ensure the copyright headers cite the code's origin.

Follow the style guide.

Opening a pull request

After cloning don't forget to git submodule update --init.

Before opening a PR make sure to:

  • have the latest Deno version installed locally
  • add tests that cover your changes.
  • deno task test passes.
  • deno fmt --check passes.
  • deno lint passes.

Give the PR a descriptive title.

Examples of good titles:

  • fix(http): Fix race condition in server
  • docs(fmt): Update docstrings
  • feat(log): Handle nested messages

Examples of bad titles:

  • fix #7123
  • update docs
  • fix bugs

Ensure there is a related issue and it is referenced in the PR text.

For contributions to the Node compatibility library please check the std/node contributing guide

About CI checks:

We currently have 9 checks on CI. Each PR should pass all of these checks to be accepted.

  • test with Deno canary on Windows
  • test with Deno canary on Linux
  • test with Deno canary on macOS
  • test Node polyfill with Deno canary on Windows
  • test Node polyfill with Deno canary on Linux
  • test Node polyfill with Deno canary on macOS
  • lint
  • wasm crypto check
  • CLA

Typechecking code in Markdown files:

If you want to run deno test --doc you will need to specify the flag --import-map=test_import_map.json, this import map is in the root of deno_std.

For maintainers:

To release a new version a tag in the form of x.y.z should be added.