diff --git a/.cspell.json b/.cspell.json
index 17708557..5f1a69a3 100644
--- a/.cspell.json
+++ b/.cspell.json
@@ -30,7 +30,7 @@
     "patches/",
     "yarn.lock"
   ],
-  "ignoreRegExpList": [],
+  "ignoreRegExpList": ["/data:.+;base64,.+/"],
   "ignoreWords": [],
   "language": "en-US",
   "patterns": [],
diff --git a/README.md b/README.md
index 5a00210a..6d59ad29 100644
--- a/README.md
+++ b/README.md
@@ -68,6 +68,7 @@ import {
   defaultMainFields,
   extensionFormatMap,
   formats,
+  getSource,
   isAbsoluteSpecifier,
   isArrayIndex,
   isBareSpecifier,
@@ -106,6 +107,7 @@ This package exports the following identifiers:
 - [`defaultMainFields`](./src/lib/default-main-fields.mts)
 - [`extensionFormatMap`](./src/lib/extension-format-map.mts)
 - [`formats`](./src/lib/formats.mts)
+- [`getSource`](./src/lib/get-source.mts)
 - [`isAbsoluteSpecifier`](./src/lib/is-absolute-specifier.mts)
 - [`isArrayIndex`](./src/lib/is-array-index.mts)
 - [`isBareSpecifier`](./src/lib/is-bare-specifier.mts)
diff --git a/eslint.base.config.mjs b/eslint.base.config.mjs
index 1033df69..0a05b4af 100644
--- a/eslint.base.config.mjs
+++ b/eslint.base.config.mjs
@@ -171,10 +171,12 @@ export default [
       globals: {
         ...globals.es2024,
         ...globals.node,
+        BufferEncoding: 'readonly',
         Chai: 'readonly',
         Console: 'readonly',
         NodeJS: 'readonly',
-        React: fs.existsSync('node_modules/react') ? 'readonly' : false
+        React: fs.existsSync('node_modules/react') ? 'readonly' : false,
+        RequestInit: 'readonly'
       },
       parser: /** @type {Parser} */ (ts.parser),
       parserOptions: {
diff --git a/package.json b/package.json
index 3716764c..fda63702 100644
--- a/package.json
+++ b/package.json
@@ -63,6 +63,18 @@
       "node": "fs",
       "default": "fs"
     },
+    "#internal/process": {
+      "types": {
+        "mlly": "./src/internal/process.d.mts",
+        "default": "./dist/internal/process.d.mts"
+      },
+      "browser": {
+        "mlly": "./src/internal/process.browser.mts",
+        "default": "./dist/internal/process.browser.mjs"
+      },
+      "node": "process",
+      "default": "process"
+    },
     "#internal/*": {
       "mlly": "./src/internal/*.mts",
       "default": "./dist/internal/*.mjs"
diff --git a/src/__snapshots__/index.e2e.snap b/src/__snapshots__/index.e2e.snap
index 6a50ad39..8294d058 100644
--- a/src/__snapshots__/index.e2e.snap
+++ b/src/__snapshots__/index.e2e.snap
@@ -9,6 +9,7 @@ exports[`e2e:mlly > should expose public api 1`] = `
   "defaultMainFields",
   "extensionFormatMap",
   "formats",
+  "getSource",
   "isAbsoluteSpecifier",
   "isArrayIndex",
   "isBareSpecifier",
diff --git a/src/interfaces/__tests__/context-get-source.spec-d.mts b/src/interfaces/__tests__/context-get-source.spec-d.mts
new file mode 100644
index 00000000..466524d8
--- /dev/null
+++ b/src/interfaces/__tests__/context-get-source.spec-d.mts
@@ -0,0 +1,43 @@
+/**
+ * @file Type Tests - GetSourceContext
+ * @module mlly/interfaces/tests/unit-d/GetSourceContext
+ */
+
+import type TestSubject from '#interfaces/context-get-source'
+import type {
+  FileSystem,
+  GetSourceHandlers,
+  GetSourceOptions
+} from '@flex-development/mlly'
+
+describe('unit-d:interfaces/GetSourceContext', () => {
+  it('should extend GetSourceOptions', () => {
+    expectTypeOf<TestSubject>().toMatchTypeOf<GetSourceOptions>()
+  })
+
+  it('should match [error: boolean]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('error').toEqualTypeOf<boolean>()
+  })
+
+  it('should match [fs: FileSystem]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('fs').toEqualTypeOf<FileSystem>()
+  })
+
+  it('should match [handlers: GetSourceHandlers]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('handlers')
+      .toEqualTypeOf<GetSourceHandlers>()
+  })
+
+  it('should match [req: RequestInit]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('req')
+      .toEqualTypeOf<RequestInit>()
+  })
+
+  it('should match [schemes: Set<string>', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('schemes')
+      .toEqualTypeOf<Set<string>>()
+  })
+})
diff --git a/src/interfaces/__tests__/options-get-source.spec-d.mts b/src/interfaces/__tests__/options-get-source.spec-d.mts
new file mode 100644
index 00000000..d9c43a25
--- /dev/null
+++ b/src/interfaces/__tests__/options-get-source.spec-d.mts
@@ -0,0 +1,54 @@
+/**
+ * @file Type Tests - GetSourceOptions
+ * @module mlly/interfaces/tests/unit-d/GetSourceOptions
+ */
+
+import type TestSubject from '#interfaces/options-get-source'
+import type {
+  FileSystem,
+  GetSourceHandlers,
+  ModuleFormat
+} from '@flex-development/mlly'
+import type { Nilable } from '@flex-development/tutils'
+
+describe('unit-d:interfaces/GetSourceOptions', () => {
+  it('should allow empty object', () => {
+    assertType<TestSubject>({})
+  })
+
+  it('should match [format?: ModuleFormat | null | undefined]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('format')
+      .toEqualTypeOf<Nilable<ModuleFormat>>()
+  })
+
+  it('should match [fs?: FileSystem | null | undefined]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('fs')
+      .toEqualTypeOf<Nilable<FileSystem>>()
+  })
+
+  it('should match [handlers?: GetSourceHandlers | null | undefined]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('handlers')
+      .toEqualTypeOf<Nilable<GetSourceHandlers>>()
+  })
+
+  it('should match [ignoreErrors?: boolean | null | undefined]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('ignoreErrors')
+      .toEqualTypeOf<Nilable<boolean>>()
+  })
+
+  it('should match [req?: RequestInit | null | undefined]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('req')
+      .toEqualTypeOf<Nilable<RequestInit>>()
+  })
+
+  it('should match [schemes?: Set<string> | readonly string[] | null | undefined]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('schemes')
+      .toEqualTypeOf<Nilable<Set<string> | readonly string[]>>()
+  })
+})
diff --git a/src/interfaces/__tests__/protocol-map.spec-d.mts b/src/interfaces/__tests__/protocol-map.spec-d.mts
index ea6d37c6..5eb8c92f 100644
--- a/src/interfaces/__tests__/protocol-map.spec-d.mts
+++ b/src/interfaces/__tests__/protocol-map.spec-d.mts
@@ -6,79 +6,91 @@
 import type TestSubject from '#interfaces/protocol-map'
 
 describe('unit-d:interfaces/ProtocolMap', () => {
-  it('should have property "blob:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('blob:')
+  it('should match [blob: "blob:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('blob').toEqualTypeOf<'blob:'>()
   })
 
-  it('should have property "content:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('content:')
+  it('should match [content: "content:"]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('content')
+      .toEqualTypeOf<'content:'>()
   })
 
-  it('should have property "cvs:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('cvs:')
+  it('should match [cvs: "cvs:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('cvs').toEqualTypeOf<'cvs:'>()
   })
 
-  it('should have property "data:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('data:')
+  it('should match [data: "data:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('data').toEqualTypeOf<'data:'>()
   })
 
-  it('should have property "dns:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('dns:')
+  it('should match [dns: "dns:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('dns').toEqualTypeOf<'dns:'>()
   })
 
-  it('should have property "file:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('file:')
+  it('should match [file: "file:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('file').toEqualTypeOf<'file:'>()
   })
 
-  it('should have property "fish:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('fish:')
+  it('should match [fish: "fish:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('fish').toEqualTypeOf<'fish:'>()
   })
 
-  it('should have property "ftp:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('ftp:')
+  it('should match [ftp: "ftp:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('ftp').toEqualTypeOf<'ftp:'>()
   })
 
-  it('should have property "git:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('git:')
+  it('should match [git: "git:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('git').toEqualTypeOf<'git:'>()
   })
 
-  it('should have property "http:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('http:')
+  it('should match [http: "http:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('http').toEqualTypeOf<'http:'>()
   })
 
-  it('should have property "https:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('https:')
+  it('should match [https: "https:"]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('https')
+      .toEqualTypeOf<'https:'>()
   })
 
-  it('should have property "mvn:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('mvn:')
+  it('should match [mvn: "mvn:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('mvn').toEqualTypeOf<'mvn:'>()
   })
 
-  it('should have property "redis:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('redis:')
+  it('should match [node: "node:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('node').toEqualTypeOf<'node:'>()
   })
 
-  it('should have property "sftp:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('sftp:')
+  it('should match [redis: "redis:"]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('redis')
+      .toEqualTypeOf<'redis:'>()
   })
 
-  it('should have property "ssh:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('ssh:')
+  it('should match [sftp: "sftp:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('sftp').toEqualTypeOf<'sftp:'>()
   })
 
-  it('should have property "svn:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('svn:')
+  it('should match [ssh: "ssh:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('ssh').toEqualTypeOf<'ssh:'>()
   })
 
-  it('should have property "view-source:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('view-source:')
+  it('should match [svn: "svn:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('svn').toEqualTypeOf<'svn:'>()
   })
 
-  it('should have property "ws:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('ws:')
+  it('should match [viewSource: "view-source:"]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty('viewSource')
+      .toEqualTypeOf<'view-source:'>()
   })
 
-  it('should have property "wss:"', () => {
-    expectTypeOf<TestSubject>().toHaveProperty('wss:')
+  it('should match [ws: "ws:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('ws').toEqualTypeOf<'ws:'>()
+  })
+
+  it('should match [wss: "wss:"]', () => {
+    expectTypeOf<TestSubject>().toHaveProperty('wss').toEqualTypeOf<'wss:'>()
   })
 })
diff --git a/src/interfaces/context-get-source.mts b/src/interfaces/context-get-source.mts
new file mode 100644
index 00000000..7b767d54
--- /dev/null
+++ b/src/interfaces/context-get-source.mts
@@ -0,0 +1,63 @@
+/**
+ * @file Interfaces - GetSourceContext
+ * @module mlly/interfaces/GetSourceContext
+ */
+
+import type {
+  FileSystem,
+  GetSourceHandlers,
+  GetSourceOptions
+} from '@flex-development/mlly'
+
+/**
+ * Source code retrieval context.
+ *
+ * @see {@linkcode GetSourceOptions}
+ *
+ * @extends {GetSourceOptions}
+ */
+interface GetSourceContext extends GetSourceOptions {
+  /**
+   * Throw [`ERR_UNSUPPORTED_ESM_URL_SCHEME`][err]?
+   *
+   * [err]: https://nodejs.org/api/errors.html#err_unsupported_esm_url_scheme
+   */
+  error: boolean
+
+  /**
+   * File system API.
+   *
+   * @see {@linkcode FileSystem}
+   *
+   * @override
+   */
+  fs: FileSystem
+
+  /**
+   * URL handler map.
+   *
+   * @see {@linkcode GetSourceHandlers}
+   *
+   * @override
+   */
+  handlers: GetSourceHandlers
+
+  /**
+   * Request options for network based modules.
+   *
+   * > 👉 **Note**: Only applicable if {@linkcode network} is
+   * > enabled.
+   *
+   * @override
+   */
+  req: RequestInit
+
+  /**
+   * List of supported URL schemes.
+   *
+   * @override
+   */
+  schemes: Set<string>
+}
+
+export type { GetSourceContext as default }
diff --git a/src/interfaces/index.mts b/src/interfaces/index.mts
index 3a5ab6ee..5d7084db 100644
--- a/src/interfaces/index.mts
+++ b/src/interfaces/index.mts
@@ -4,9 +4,15 @@
  */
 
 export type { default as Aliases } from '#interfaces/aliases'
+export type {
+  default as GetSourceContext
+} from '#interfaces/context-get-source'
 export type { default as FileSystem } from '#interfaces/file-system'
 export type { default as MainFieldMap } from '#interfaces/main-field-map'
 export type { default as ModuleFormatMap } from '#interfaces/module-format-map'
+export type {
+  default as GetSourceOptions
+} from '#interfaces/options-get-source'
 export type {
   default as ResolveAliasOptions
 } from '#interfaces/options-resolve-alias'
diff --git a/src/interfaces/options-get-source.mts b/src/interfaces/options-get-source.mts
new file mode 100644
index 00000000..24d27725
--- /dev/null
+++ b/src/interfaces/options-get-source.mts
@@ -0,0 +1,59 @@
+/**
+ * @file Interfaces - GetSourceOptions
+ * @module mlly/interfaces/GetSourceOptions
+ */
+
+import type {
+  FileSystem,
+  GetSourceHandlers,
+  ModuleFormat
+} from '@flex-development/mlly'
+
+/**
+ * Source code retrieval options.
+ */
+interface GetSourceOptions {
+  /**
+   * Module format hint.
+   *
+   * @see {@linkcode ModuleFormat}
+   */
+  format?: ModuleFormat | null | undefined
+
+  /**
+   * File system API.
+   *
+   * @see {@linkcode FileSystem}
+   */
+  fs?: FileSystem | null | undefined
+
+  /**
+   * URL handler map.
+   *
+   * @see {@linkcode GetSourceHandlers}
+   */
+  handlers?: GetSourceHandlers | null | undefined
+
+  /**
+   * Ignore [`ERR_UNSUPPORTED_ESM_URL_SCHEME`][err] if thrown.
+   *
+   * [err]: https://nodejs.org/api/errors.html#err_unsupported_esm_url_scheme
+   */
+  ignoreErrors?: boolean | null | undefined
+
+  /**
+   * Request options for network based modules.
+   *
+   * > 👉 **Note**: Only applicable if {@linkcode network} is enabled.
+   */
+  req?: RequestInit | null | undefined
+
+  /**
+   * List of supported URL schemes.
+   *
+   * @default ['data','file','http','https','node']
+   */
+  schemes?: Set<string> | readonly string[] | null | undefined
+}
+
+export type { GetSourceOptions as default }
diff --git a/src/interfaces/protocol-map.mts b/src/interfaces/protocol-map.mts
index 9b83a706..389f97b8 100644
--- a/src/interfaces/protocol-map.mts
+++ b/src/interfaces/protocol-map.mts
@@ -11,26 +11,27 @@
  * @see https://url.spec.whatwg.org/#special-scheme
  */
 interface ProtocolMap {
-  'blob:': true
-  'content:': true
-  'cvs:': true
-  'data:': true
-  'dns:': true
-  'file:': true
-  'fish:': true
-  'ftp:': true
-  'git:': true
-  'http:': true
-  'https:': true
-  'mvn:': true
-  'redis:': true
-  'sftp:': true
-  'ssh:': true
-  'svn:': true
-  'urn:': true
-  'view-source:': true
-  'ws:': true
-  'wss:': true
+  blob: 'blob:'
+  content: 'content:'
+  cvs: 'cvs:'
+  data: 'data:'
+  dns: 'dns:'
+  file: 'file:'
+  fish: 'fish:'
+  ftp: 'ftp:'
+  git: 'git:'
+  http: 'http:'
+  https: 'https:'
+  mvn: 'mvn:'
+  node: 'node:'
+  redis: 'redis:'
+  sftp: 'sftp:'
+  ssh: 'ssh:'
+  svn: 'svn:'
+  urn: 'urn:'
+  viewSource: 'view-source:'
+  ws: 'ws:'
+  wss: 'wss:'
 }
 
 export type { ProtocolMap as default }
diff --git a/src/internal/fs.browser.mts b/src/internal/fs.browser.mts
index bf6e1fc2..cd13f789 100644
--- a/src/internal/fs.browser.mts
+++ b/src/internal/fs.browser.mts
@@ -1,6 +1,6 @@
 /**
  * @file Internal - fs/browser
- * @module mlly/lib/fs/browser
+ * @module mlly/internal/fs/browser
  */
 
 import type { FileSystem } from '@flex-development/mlly'
diff --git a/src/internal/process.browser.mts b/src/internal/process.browser.mts
new file mode 100644
index 00000000..b55915ca
--- /dev/null
+++ b/src/internal/process.browser.mts
@@ -0,0 +1,9 @@
+/**
+ * @file Internal - process/browser
+ * @module mlly/internal/process/browser
+ */
+
+export default {
+  browser: true,
+  platform: 'browser'
+}
diff --git a/src/internal/process.d.mts b/src/internal/process.d.mts
new file mode 100644
index 00000000..138acea8
--- /dev/null
+++ b/src/internal/process.d.mts
@@ -0,0 +1,4 @@
+declare module '#internal/process' {
+  const process: NodeJS.Process
+  export default process
+}
diff --git a/src/lib/__snapshots__/get-source.snap b/src/lib/__snapshots__/get-source.snap
new file mode 100644
index 00000000..203b2745
--- /dev/null
+++ b/src/lib/__snapshots__/get-source.snap
@@ -0,0 +1,3 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`unit:lib/getSource > should throw on unsupported url scheme (%#) 1`] = `[Error: Only URLs with a scheme in: file are supported by the default ESM loader. Received protocol 'git:']`;
diff --git a/src/lib/__tests__/get-source.spec.mts b/src/lib/__tests__/get-source.spec.mts
new file mode 100644
index 00000000..29abf6c2
--- /dev/null
+++ b/src/lib/__tests__/get-source.spec.mts
@@ -0,0 +1,50 @@
+/**
+ * @file Unit Tests - getSource
+ * @module mlly/lib/tests/unit/getSource
+ */
+
+import testSubject from '#lib/get-source'
+import {
+  codes,
+  isNodeError,
+  type NodeError
+} from '@flex-development/errnode'
+import pathe from '@flex-development/pathe'
+
+describe('unit:lib/getSource', () => {
+  it.each<Parameters<typeof testSubject>>([
+    ['os'],
+    [new URL('node:test')]
+  ])('should return `undefined` if `id` is builtin module (%j)', async id => {
+    expect(await testSubject(id)).to.be.undefined
+  })
+
+  it.each<Parameters<typeof testSubject>>([
+    ['data:application/javascript;base64,SGVsbG8sIFdvcmxkIQ=='],
+    ['data:text/javascript,console.log("hello!");'],
+    ['https://esm.sh/@flex-development/mlly'],
+    [pathe.fileURLToPath(import.meta.url)],
+    [pathe.pathToFileURL('build.config.mts')]
+  ])('should return source code for `id` (%#)', async (id, options) => {
+    expect(await testSubject(id, options)).to.be.a('string')
+  })
+
+  it('should throw on unsupported url scheme (%#)', async () => {
+    // Arrange
+    let error!: NodeError
+
+    // Act
+    try {
+      await testSubject('git://github.com/flex-development/mlly.git', {
+        schemes: ['file']
+      })
+    } catch (e: unknown) {
+      error = e as typeof error
+    }
+
+    // Expect
+    expect(error).to.satisfy(isNodeError)
+    expect(error).to.have.property('code', codes.ERR_UNSUPPORTED_ESM_URL_SCHEME)
+    expect(error).toMatchSnapshot()
+  })
+})
diff --git a/src/lib/can-parse-url.mts b/src/lib/can-parse-url.mts
index 13b00709..6d2caf48 100644
--- a/src/lib/can-parse-url.mts
+++ b/src/lib/can-parse-url.mts
@@ -13,19 +13,16 @@ import type { ModuleId } from '@flex-development/mlly'
  *
  * @see {@linkcode ModuleId}
  *
- * @param {ModuleId} input
+ * @param {unknown} input
  *  The absolute or relative input URL to parse
- * @param {ModuleId | null | undefined} [base]
+ * @param {unknown} [base]
  *  Base URL to resolve against if `input` is not absolute
  * @return {boolean}
  *  `true` if `input` can be parsed to a `URL`
  */
-function canParseUrl(
-  input: ModuleId,
-  base?: ModuleId | null | undefined
-): boolean {
+function canParseUrl(input: unknown, base?: unknown): boolean {
   try {
-    new URL(input, base ?? undefined)
+    new URL(input as ModuleId, (base ?? undefined) as ModuleId | undefined)
     return true
   } catch {
     return false
diff --git a/src/lib/get-source.mts b/src/lib/get-source.mts
new file mode 100644
index 00000000..ec049f81
--- /dev/null
+++ b/src/lib/get-source.mts
@@ -0,0 +1,193 @@
+/**
+ * @file getSource
+ * @module mlly/lib/getSource
+ */
+
+import fs from '#internal/fs'
+import process from '#internal/process'
+import canParseUrl from '#lib/can-parse-url'
+import isFile from '#lib/is-file'
+import {
+  ERR_UNSUPPORTED_ESM_URL_SCHEME,
+  type ErrUnsupportedEsmUrlScheme
+} from '@flex-development/errnode'
+import { isBuiltin } from '@flex-development/is-builtin'
+import type {
+  GetSourceContext,
+  GetSourceHandler,
+  GetSourceOptions,
+  ModuleId,
+  Protocol
+} from '@flex-development/mlly'
+import pathe from '@flex-development/pathe'
+import { ok } from 'devlop'
+
+export default getSource
+
+/**
+ * Get the source code for `id`.
+ *
+ * > 👉 **Note**: If `id` is not a [builtin module][builtin-module] and also
+ * > cannot be parsed as an {@linkcode URL}, it will be assumed to be a path and
+ * > converted to a [`file:` URL][file-url].
+ *
+ * [builtin-module]: https://nodejs.org/api/esm.html#builtin-modules
+ * [file-url]: https://nodejs.org/api/esm.html#file-urls
+ *
+ * @see {@linkcode ErrUnsupportedEsmUrlScheme}
+ * @see {@linkcode GetSourceOptions}
+ * @see {@linkcode ModuleId}
+ *
+ * @async
+ *
+ * @this {void}
+ *
+ * @param {ModuleId} id
+ *  Module id to handle
+ * @param {GetSourceOptions | null | undefined} [options]
+ *  Source code retrieval options
+ * @return {Promise<string | null | undefined>}
+ *  Source code for `id`
+ * @throws {ErrUnsupportedEsmUrlScheme}
+ */
+async function getSource(
+  this: void,
+  id: ModuleId,
+  options?: GetSourceOptions | null | undefined
+): Promise<string | null | undefined> {
+  /**
+   * Source code retrieval context.
+   *
+   * @const {GetSourceContext} context
+   */
+  const context: GetSourceContext = {
+    ...options,
+    error: false,
+    fs: options?.fs ?? fs,
+    handlers: {
+      'data:': data,
+      'file:': file,
+      'http:': https,
+      'https:': https,
+      'node:': node,
+      ...options?.handlers
+    },
+    req: { ...options?.req },
+    schemes: new Set(
+      options?.schemes
+        ? [...options.schemes]
+        : ['data', 'file', 'http', 'https', 'node']
+    )
+  }
+
+  /**
+   * Module url.
+   *
+   * @const {URL} url
+   */
+  const url: URL = isBuiltin(id)
+    ? new URL('node:' + String(id).replace(/^node:/, ''))
+    : canParseUrl(id)
+    ? new URL(id)
+    : (ok(typeof id === 'string', 'expected string'), pathe.pathToFileURL(id))
+
+  /**
+   * Source code handler for {@linkcode url}.
+   *
+   * @const {GetSourceHandler} handle
+   */
+  const handle: GetSourceHandler | null | undefined =
+    context.handlers[url.protocol as Protocol]
+
+  /**
+   * Source code.
+   *
+   * @var {Uint8Array | string | null | undefined} code
+   */
+  let code: Uint8Array | string | null | undefined
+
+  // get source code
+  if (handle) {
+    code = await handle.call(context, url)
+  } else {
+    context.error = true
+  }
+
+  // throw on unsupported url scheme
+  if (context.error && !context.ignoreErrors) {
+    throw new ERR_UNSUPPORTED_ESM_URL_SCHEME(
+      url,
+      [...context.schemes],
+      process.platform === 'win32'
+    )
+  }
+
+  if (code !== null && code !== undefined) code = String(code)
+  return code
+}
+
+/**
+ * @this {GetSourceContext}
+ *
+ * @param {URL} url
+ *  Module URL
+ * @return {Buffer}
+ *  Source code buffer
+ */
+function data(this: GetSourceContext, url: URL): Buffer {
+  const [mime, data = ''] = url.pathname.split(',')
+
+  ok(url.protocol === 'data:', 'expected `data:` URL')
+  ok(mime !== undefined, 'expected `mime` to be a string')
+
+  return Buffer.from(
+    decodeURIComponent(data),
+    mime.endsWith('base64') ? 'base64' : 'utf8'
+  )
+}
+
+/**
+ * @this {GetSourceContext}
+ *
+ * @param {URL} url
+ *  Module URL
+ * @return {Buffer | string | null}
+ *  Source code or `null` if module is not found
+ */
+function file(this: GetSourceContext, url: URL): Buffer | string | null {
+  ok(url.protocol === 'file:', 'expected `file:` URL')
+
+  /**
+   * Source code.
+   *
+   * @var {Buffer | string | null} code
+   */
+  let code: Buffer | string | null = null
+
+  if (isFile(url, this.fs)) code = this.fs.readFileSync(url)
+  return code
+}
+
+/**
+ * @this {GetSourceContext}
+ *
+ * @param {URL} url
+ *  Module URL
+ * @return {Promise<string>}
+ *  Source code
+ */
+async function https(this: GetSourceContext, url: URL): Promise<string> {
+  ok(/^https?:$/.test(url.protocol), 'expected `http:` or `https:` URL')
+  return (await fetch(url.href, this.req)).text()
+}
+
+/**
+ * @this {GetSourceContext}
+ *
+ * @param {URL} url
+ *  Module URL
+ * @return {undefined}
+ */
+function node(this: GetSourceContext, url: URL): undefined {
+  return void ok(url.protocol === 'node:', 'expected `node:` URL')
+}
diff --git a/src/lib/index.mts b/src/lib/index.mts
index 3d4493a4..9651d6c8 100644
--- a/src/lib/index.mts
+++ b/src/lib/index.mts
@@ -20,6 +20,7 @@ export { default as defaultExtensions } from '#lib/default-extensions'
 export { default as defaultMainFields } from '#lib/default-main-fields'
 export { default as extensionFormatMap } from '#lib/extension-format-map'
 export { default as formats } from '#lib/formats'
+export { default as getSource } from '#lib/get-source'
 export { default as isAbsoluteSpecifier } from '#lib/is-absolute-specifier'
 export { default as isArrayIndex } from '#lib/is-array-index'
 export { default as isBareSpecifier } from '#lib/is-bare-specifier'
diff --git a/src/types/__tests__/awaitable.spec-d.mts b/src/types/__tests__/awaitable.spec-d.mts
new file mode 100644
index 00000000..c4307b48
--- /dev/null
+++ b/src/types/__tests__/awaitable.spec-d.mts
@@ -0,0 +1,18 @@
+/**
+ * @file Type Tests - Awaitable
+ * @module mlly/types/tests/unit-d/Awaitable
+ */
+
+import type TestSubject from '#types/awaitable'
+
+describe('unit-d:types/Awaitable', () => {
+  type T = Uint8Array | string | null | undefined
+
+  it('should extract PromiseLike<T>', () => {
+    expectTypeOf<TestSubject<T>>().extract<PromiseLike<T>>().not.toBeNever()
+  })
+
+  it('should extract T', () => {
+    expectTypeOf<TestSubject<T>>().extract<T>().not.toBeNever()
+  })
+})
diff --git a/src/types/__tests__/get-source-handler.spec-d.mts b/src/types/__tests__/get-source-handler.spec-d.mts
new file mode 100644
index 00000000..464a761e
--- /dev/null
+++ b/src/types/__tests__/get-source-handler.spec-d.mts
@@ -0,0 +1,27 @@
+/**
+ * @file Type Tests - GetSourceHandler
+ * @module mlly/types/tests/unit-d/GetSourceHandler
+ */
+
+import type TestSubject from '#types/get-source-handler'
+import type { Awaitable, GetSourceContext } from '@flex-development/mlly'
+
+describe('unit-d:types/GetSourceHandler', () => {
+  it('should match [this: GetSourceContext]', () => {
+    expectTypeOf<TestSubject>().thisParameter.toEqualTypeOf<GetSourceContext>()
+  })
+
+  describe('parameters', () => {
+    it('should be callable with [URL]', () => {
+      expectTypeOf<TestSubject>().parameters.toEqualTypeOf<[URL]>()
+    })
+  })
+
+  describe('returns', () => {
+    it('should return Awaitable<Uint8Array | string | null | undefined>', () => {
+      expectTypeOf<TestSubject>()
+        .returns
+        .toEqualTypeOf<Awaitable<Uint8Array | string | null | undefined>>()
+    })
+  })
+})
diff --git a/src/types/__tests__/get-source-handlers.spec-d.mts b/src/types/__tests__/get-source-handlers.spec-d.mts
new file mode 100644
index 00000000..2032b46f
--- /dev/null
+++ b/src/types/__tests__/get-source-handlers.spec-d.mts
@@ -0,0 +1,16 @@
+/**
+ * @file Type Tests - GetSourceHandlers
+ * @module mlly/types/tests/unit-d/GetSourceHandlers
+ */
+
+import type TestSubject from '#types/get-source-handlers'
+import type { GetSourceHandler, Protocol } from '@flex-development/mlly'
+import type { Nilable } from '@flex-development/tutils'
+
+describe('unit-d:types/GetSourceHandlers', () => {
+  it('should match [[key: Protocol]: GetSourceHandler | null | undefined]', () => {
+    expectTypeOf<TestSubject>()
+      .toHaveProperty<Protocol>('' as Protocol)
+      .toEqualTypeOf<Nilable<GetSourceHandler>>()
+  })
+})
diff --git a/src/types/__tests__/protocol.spec-d.mts b/src/types/__tests__/protocol.spec-d.mts
index 4c424b91..7f20c6b0 100644
--- a/src/types/__tests__/protocol.spec-d.mts
+++ b/src/types/__tests__/protocol.spec-d.mts
@@ -7,8 +7,7 @@ import type TestSubject from '#types/protocol'
 import type { ProtocolMap } from '@flex-development/mlly'
 
 describe('unit-d:types/Protocol', () => {
-  it('should equal Extract<keyof ProtocolMap, string>', () => {
-    expectTypeOf<TestSubject>()
-      .toEqualTypeOf<Extract<keyof ProtocolMap, string>>()
+  it('should equal ProtocolMap[keyof ProtocolMap]', () => {
+    expectTypeOf<TestSubject>().toEqualTypeOf<ProtocolMap[keyof ProtocolMap]>()
   })
 })
diff --git a/src/types/awaitable.mts b/src/types/awaitable.mts
new file mode 100644
index 00000000..5babe042
--- /dev/null
+++ b/src/types/awaitable.mts
@@ -0,0 +1,16 @@
+/**
+ * @file Type Aliases - Awaitable
+ * @module mlly/types/Awaitable
+ */
+
+/**
+ * Create a union of `T` and a `T` as a promise-like value.
+ *
+ * @see {@linkcode PromiseLike}
+ *
+ * @template {any} T
+ *  Value
+ */
+type Awaitable<T> = PromiseLike<T> | T
+
+export type { Awaitable as default }
diff --git a/src/types/get-source-handler.mts b/src/types/get-source-handler.mts
new file mode 100644
index 00000000..539d7624
--- /dev/null
+++ b/src/types/get-source-handler.mts
@@ -0,0 +1,27 @@
+/**
+ * @file Type Aliases - GetSourceHandler
+ * @module mlly/types/GetSourceHandler
+ */
+
+import type { Awaitable, GetSourceContext } from '@flex-development/mlly'
+
+/**
+ * Get the source code for `url`.
+ *
+ * @see {@linkcode Awaitable}
+ * @see {@linkcode GetSourceContext}
+ * @see {@linkcode URL}
+ *
+ * @this {GetSourceContext}
+ *
+ * @param {URL} url
+ *  Module URL
+ * @return {Awaitable<Uint8Array | string | null | undefined>}
+ *  Source code
+ */
+type GetSourceHandler = (
+  this: GetSourceContext,
+  url: URL
+) => Awaitable<Uint8Array | string | null | undefined>
+
+export type { GetSourceHandler as default }
diff --git a/src/types/get-source-handlers.mts b/src/types/get-source-handlers.mts
new file mode 100644
index 00000000..b0ccd722
--- /dev/null
+++ b/src/types/get-source-handlers.mts
@@ -0,0 +1,20 @@
+/**
+ * @file Type Aliases - GetSourceHandlers
+ * @module mlly/types/GetSourceHandlers
+ */
+
+import type { GetSourceHandler, Protocol } from '@flex-development/mlly'
+
+/**
+ * Map where key is a URL protocol, and each value is `null`, `undefined`, or a
+ * source code handler.
+ *
+ * @see {@linkcode GetSourceHandler}
+ * @see {@linkcode Protocol}
+ */
+type GetSourceHandlers = Partial<Record<
+  Protocol,
+  GetSourceHandler | null | undefined
+>>
+
+export type { GetSourceHandlers as default }
diff --git a/src/types/index.mts b/src/types/index.mts
index 2d3049dd..05959f1e 100644
--- a/src/types/index.mts
+++ b/src/types/index.mts
@@ -3,7 +3,10 @@
  * @module mlly/types
  */
 
+export type { default as Awaitable } from '#types/awaitable'
 export type { default as ChangeExtFn } from '#types/change-ext-fn'
+export type { default as GetSourceHandler } from '#types/get-source-handler'
+export type { default as GetSourceHandlers } from '#types/get-source-handlers'
 export type { default as MainField } from '#types/main-field'
 export type { default as ModuleFormat } from '#types/module-format'
 export type { default as ModuleId } from '#types/module-id'
diff --git a/src/types/protocol.mts b/src/types/protocol.mts
index 6a57aa1b..b85b6971 100644
--- a/src/types/protocol.mts
+++ b/src/types/protocol.mts
@@ -11,6 +11,6 @@ import type { ProtocolMap } from '@flex-development/mlly'
  * To register new protocols, augment {@linkcode ProtocolMap}. They will be
  * added to this union automatically.
  */
-type Protocol = Extract<keyof ProtocolMap, string>
+type Protocol = ProtocolMap[keyof ProtocolMap]
 
 export type { Protocol as default }
diff --git a/tsconfig.build.json b/tsconfig.build.json
index 848147bb..82c00b07 100644
--- a/tsconfig.build.json
+++ b/tsconfig.build.json
@@ -4,19 +4,21 @@
     "allowJs": false,
     "checkJs": false,
     "customConditions": ["mlly"],
-    "declaration": true,
+    "declarationMap": false,
     "noEmitOnError": true,
     "outDir": "./dist",
     "paths": {},
     "rootDir": "./src",
     "skipLibCheck": true,
+    "sourceMap": false,
     "target": "es2023"
   },
   "exclude": ["**/__tests__/**"],
   "extends": "./tsconfig.json",
   "files": [
-    "typings/@flex-development/pkg-types/index.d.mts",
-    "typings/typescript/lib.es5.d.ts"
+    "./typings/@flex-development/pkg-types/index.d.mts",
+    "./typings/node/process.d.ts",
+    "./typings/typescript/lib.es5.d.ts"
   ],
-  "include": ["./dist/**/*", "./src/**/*"]
+  "include": ["./dist/**/*", "./src/**/**.mts"]
 }
diff --git a/tsconfig.json b/tsconfig.json
index 54d5932d..99a5262d 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -7,8 +7,8 @@
     "alwaysStrict": true,
     "checkJs": true,
     "customConditions": ["mlly", "development"],
-    "declaration": false,
-    "declarationMap": false,
+    "declaration": true,
+    "declarationMap": true,
     "emitDecoratorMetadata": false,
     "esModuleInterop": true,
     "exactOptionalPropertyTypes": true,
diff --git a/tsconfig.typecheck.json b/tsconfig.typecheck.json
index ee6ae2bd..c8cf85e2 100644
--- a/tsconfig.typecheck.json
+++ b/tsconfig.typecheck.json
@@ -9,6 +9,7 @@
   "files": [
     "./typings/@faker-js/faker/global.d.ts",
     "./typings/@flex-development/pkg-types/index.d.mts",
+    "./typings/node/process.d.ts",
     "./typings/typescript/lib.es5.d.ts",
     "./vitest-env.d.mts"
   ],
diff --git a/typings/node/process.d.ts b/typings/node/process.d.ts
new file mode 100644
index 00000000..99eb55e6
--- /dev/null
+++ b/typings/node/process.d.ts
@@ -0,0 +1,5 @@
+declare namespace NodeJS {
+  interface Process {
+    browser?: boolean | null | undefined
+  }
+}