Configuration File

Deno supports a configuration file that allows you to customize the built-in TypeScript compiler, formatter, and linter.

The configuration file supports .json and .jsonc extensions. Since v1.18, Deno will automatically detect a deno.json or deno.jsonc configuration file if it's in your current working directory or parent directories. The --config flag can be used to specify a different configuration file.

⚠️ Before Deno v1.23 you needed to supply an explicit --config flag.

imports and scopes

Since version 1.30, the deno.json configuration file acts as an import map for resolving bare specifiers.

{
  "imports": {
    "std/": "https://deno.land/std@0.181.0/"
  },
  "tasks": {
    "dev": "deno run --watch main.ts"
  }
}

See the import map section for more information on import maps.

Then your script can use the bare specifier std:

import { assertEquals } from "std/testing/assert.ts";

assertEquals(1, 2);

The top-level deno.json option importMap along with the --importmap flag can be used to specify the import map in other files.

tasks

Similar to package.json's script field. Essentially shortcuts for command line invocations.

{
  "tasks": {
    "start": "deno run -A --watch=static/,routes/,data/ dev.ts"
  }
}

Using deno task start will run the command. See also deno task.

lint

Configuration for deno lint.

{
  "lint": {
    "files": {
      "include": ["src/"],
      "exclude": ["src/testdata/"]
    },
    "rules": {
      "tags": ["recommended"],
      "include": ["ban-untagged-todo"],
      "exclude": ["no-unused-vars"]
    }
  }
}

fmt

Configuration for deno fmt

{
  "fmt": {
    "files": {
      "include": ["src/"],
      "exclude": ["src/testdata/"]
    },
    "options": {
      "useTabs": true,
      "lineWidth": 80,
      "indentWidth": 4,
      "singleQuote": true,
      "proseWrap": "preserve"
    }
  }
}

lock

Used to specify a different file name for the lockfile. By default deno will use deno.lock and place it alongside the configuration file.

compilerOptions

deno.json can also act as a TypeScript configuration file and supports most of the TS compiler options.

Deno encourages users to use the default TypeScript configuration to help sharing code.

See also Configuring TypeScript in Deno.

Full example

{
  "compilerOptions": {
    "allowJs": true,
    "lib": ["deno.window"],
    "strict": true
  },
  "lint": {
    "files": {
      "include": ["src/"],
      "exclude": ["src/testdata/"]
    },
    "rules": {
      "tags": ["recommended"],
      "include": ["ban-untagged-todo"],
      "exclude": ["no-unused-vars"]
    }
  },
  "fmt": {
    "files": {
      "include": ["src/"],
      "exclude": ["src/testdata/"]
    },
    "options": {
      "useTabs": true,
      "lineWidth": 80,
      "indentWidth": 4,
      "semiColons": false,
      "singleQuote": true,
      "proseWrap": "preserve"
    }
  },
  "test": {
    "files": {
      "include": ["src/"],
      "exclude": ["src/testdata/"]
    }
  }
}

JSON schema

A JSON schema file is available for editors to provide autocompletion. The file is versioned and available at: https://deno.land/x/deno/cli/schemas/config-file.v1.json