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deno serve

Command line usage:
deno serve [OPTIONS] [SCRIPT_ARG]...

Run a server defined in a main module

The serve command uses the default exports of the main module to determine which servers to start.

Start a server defined in server.ts:

deno serve server.ts

Start a server defined in server.ts, watching for changes and running on port 5050:

deno serve --watch --port 5050 server.ts

Type checking options

--check

Enable type-checking. This subcommand does not type-check by default If the value of "all" is supplied, remote modules will be included. Alternatively, the 'deno check' subcommand can be used.

--no-check

Skip type-checking. If the value of "remote" is supplied, diagnostic errors from remote modules will be ignored.

Dependency management options

--cached-only

Require that remote dependencies are already cached.

--frozen

Error out if lockfile is out of date.

--import-map

Load import map file from local file or remote URL.

--lock

Check the specified lock file. (If value is not provided, defaults to "./deno.lock").

--no-lock

Disable auto discovery of the lock file.

--no-npm

Do not resolve npm modules.

--no-remote

Do not resolve remote modules.

--node-modules-dir

Sets the node modules management mode for npm packages.

--reload

Short flag: -r

Reload source code cache (recompile TypeScript) no value Reload everything jsr:@std/http/file-server,jsr:@std/assert/assert-equals Reloads specific modules npm: Reload all npm modules npm:chalk Reload specific npm module.

--vendor

Toggles local vendor folder usage for remote modules and a node_modules folder for npm packages.

Options

--allow-scripts

Allow running npm lifecycle scripts for the given packages Note: Scripts will only be executed when using a node_modules directory (--node-modules-dir).

--cert

Load certificate authority from PEM encoded file.

--conditions

Use this argument to specify custom conditions for npm package exports. You can also use DENO_CONDITIONS env var. .

--config

Short flag: -c

Configure different aspects of deno including TypeScript, linting, and code formatting. Typically the configuration file will be called deno.json or deno.jsonc and automatically detected; in that case this flag is not necessary.

--env-file

Load environment variables from local file Only the first environment variable with a given key is used. Existing process environment variables are not overwritten, so if variables with the same names already exist in the environment, their values will be preserved. Where multiple declarations for the same environment variable exist in your .env file, the first one encountered is applied. This is determined by the order of the files you pass as arguments.

--ext

Set content type of the supplied file.

--host

The TCP address to serve on, defaulting to 0.0.0.0 (all interfaces).

--location

Value of globalThis.location used by some web APIs.

--no-code-cache

Disable V8 code cache feature.

--no-config

Disable automatic loading of the configuration file.

--open

Open the browser on the address that the server is running on.

--parallel

Run multiple server workers in parallel. Parallelism defaults to the number of available CPUs or the value of the DENO_JOBS environment variable.

--port

The TCP port to serve on. Pass 0 to pick a random free port [default: 8000]

--preload

A list of files that will be executed before the main module.

--seed

Set the random number generator seed.

--v8-flags

To see a list of all available flags use --v8-flags=--help Flags can also be set via the DENO_V8_FLAGS environment variable. Any flags set with this flag are appended after the DENO_V8_FLAGS environment variable.

Debugging options

--inspect

Activate inspector on host:port [default: 127.0.0.1:9229]

--inspect-brk

Activate inspector on host:port, wait for debugger to connect and break at the start of user script.

--inspect-wait

Activate inspector on host:port and wait for debugger to connect before running user code.

File watching options

--no-clear-screen

Do not clear terminal screen when under watch mode.

--watch

Watch for file changes and restart process automatically. Local files from entry point module graph are watched by default. Additional paths might be watched by passing them as arguments to this flag.

--watch-exclude

Exclude provided files/patterns from watch mode.

--watch-hmr

Watch for file changes and restart process automatically. Local files from entry point module graph are watched by default. Additional paths might be watched by passing them as arguments to this flag.

Example

Here's an example of how you can create a simple HTTP server with declarative fetch:

server.ts
export default {
  async fetch(_req) {
    return new Response("Hello world!");
  },
} satisfies Deno.ServeDefaultExport;

The satisfies Deno.ServeDefaultExport type assertion ensures that your exported object conforms to the expected interface for Deno's HTTP server. This provides type safety and better editor autocomplete while allowing you to maintain the inferred types of your implementation.

You can then run the server using the deno serve command:

deno serve server.ts

The logic inside the fetch function can be customized to handle different types of requests and serve content accordingly:

server.ts
export default {
  async fetch(request) {
    if (request.url.endsWith("/json")) {
      return Response.json({ hello: "world" });
    }

    return new Response("Hello world!");
  },
} satisfies Deno.ServeDefaultExport;

© 2018–2025 the Deno authors
Licensed under the MIT License.
https://docs.deno.com/runtime/reference/cli/serve