diff --git a/src/auth.spec.ts b/src/auth.spec.ts
deleted file mode 100644
index f5ee907..0000000
--- a/src/auth.spec.ts
+++ /dev/null
@@ -1,139 +0,0 @@
-import { describe, it, assert } from 'vitest';
-import auth from './index';
-
-function request(authorization?: string) {
-  return {
-    headers: {
-      authorization: authorization,
-    },
-  };
-}
-
-describe('auth(req)', function () {
-  describe('arguments', function () {
-    describe('req', function () {
-      it('should be required', function () {
-        assert.throws(auth as any, /argument req is required/);
-      });
-
-      it('should accept a request', function () {
-        var req = request('basic Zm9vOmJhcg==');
-        var creds = auth(req);
-        assert.strictEqual(creds?.name, 'foo');
-        assert.strictEqual(creds?.pass, 'bar');
-      });
-
-      it('should reject null', function () {
-        assert.throws(auth.bind(null, null as any), /argument req is required/);
-      });
-
-      it('should reject a number', function () {
-        assert.throws(auth.bind(null, 42 as any), /argument req is required/);
-      });
-
-      it('should reject an object without headers', function () {
-        assert.throws(auth.bind(null, {}), /argument req is required/);
-      });
-    });
-  });
-
-  describe('with no Authorization field', function () {
-    it('should return undefined', function () {
-      var req = request();
-      assert.strictEqual(auth(req), undefined);
-    });
-  });
-
-  describe('with malformed Authorization field', function () {
-    it('should return undefined', function () {
-      var req = request('Something');
-      assert.strictEqual(auth(req), undefined);
-    });
-  });
-
-  describe('with malformed Authorization scheme', function () {
-    it('should return undefined', function () {
-      var req = request('basic_Zm9vOmJhcg==');
-      assert.strictEqual(auth(req), undefined);
-    });
-  });
-
-  describe('with malformed credentials', function () {
-    it('should return undefined', function () {
-      var req = request('basic Zm9vcgo=');
-      assert.strictEqual(auth(req), undefined);
-    });
-  });
-
-  describe('with valid credentials', function () {
-    it('should return .name and .pass', function () {
-      var req = request('basic Zm9vOmJhcg==');
-      var creds = auth(req);
-      assert.strictEqual(creds?.name, 'foo');
-      assert.strictEqual(creds?.pass, 'bar');
-    });
-  });
-
-  describe('with empty password', function () {
-    it('should return .name and .pass', function () {
-      var req = request('basic Zm9vOg==');
-      var creds = auth(req);
-      assert.strictEqual(creds?.name, 'foo');
-      assert.strictEqual(creds?.pass, '');
-    });
-  });
-
-  describe('with empty userid', function () {
-    it('should return .name and .pass', function () {
-      var req = request('basic OnBhc3M=');
-      var creds = auth(req);
-      assert.strictEqual(creds?.name, '');
-      assert.strictEqual(creds?.pass, 'pass');
-    });
-  });
-
-  describe('with empty userid and pass', function () {
-    it('should return .name and .pass', function () {
-      var req = request('basic Og==');
-      var creds = auth(req);
-      assert.strictEqual(creds?.name, '');
-      assert.strictEqual(creds?.pass, '');
-    });
-  });
-
-  describe('with colon in pass', function () {
-    it('should return .name and .pass', function () {
-      var req = request('basic Zm9vOnBhc3M6d29yZA==');
-      var creds = auth(req);
-      assert.strictEqual(creds?.name, 'foo');
-      assert.strictEqual(creds?.pass, 'pass:word');
-    });
-  });
-
-  describe('with scheme "Basic"', function () {
-    it('should return .name and .pass', function () {
-      var req = request('Basic Zm9vOmJhcg==');
-      var creds = auth(req);
-      assert.strictEqual(creds?.name, 'foo');
-      assert.strictEqual(creds?.pass, 'bar');
-    });
-  });
-
-  describe('with scheme "BASIC"', function () {
-    it('should return .name and .pass', function () {
-      var req = request('BASIC Zm9vOmJhcg==');
-      var creds = auth(req);
-      assert.strictEqual(creds?.name, 'foo');
-      assert.strictEqual(creds?.pass, 'bar');
-    });
-  });
-
-  describe('with scheme "BaSiC"', function () {
-    it('should return .name and .pass', function () {
-      var req = request('BaSiC Zm9vOmJhcg==');
-      var creds = auth(req);
-      assert.strictEqual(creds?.name, 'foo');
-      assert.strictEqual(creds?.pass, 'bar');
-    });
-  });
-});
diff --git a/src/index.ts b/src/index.ts
index 98bc6c4..6576a46 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -8,74 +8,43 @@
 
 import { Buffer } from 'node:buffer';
 
-export = auth;
+/**
+ * Object to represent user credentials.
+ */
+export interface Credentials {
+  name: string;
+  pass: string;
+}
 
 /**
- * Parse the Authorization header field of a request
+ * Parse basic auth to object.
+ *
+ * @param {string} string
+ * @return {object}
  * @public
  */
 
-function auth(req: auth.IncomingMessageLike): auth.Credentials | undefined {
-  if (!req) {
-    throw new TypeError('argument req is required');
+export function parse(string: string): Credentials | undefined {
+  if (typeof string !== 'string') {
+    return undefined;
   }
 
-  if (typeof req !== 'object') {
-    throw new TypeError('argument req is required to be an object');
-  }
-
-  // get header
-  const header = getAuthorization(req);
-
   // parse header
-  return auth.parse(header ?? '');
-}
+  const match = CREDENTIALS_REGEXP.exec(string);
 
-namespace auth {
-  /**
-   * Object to represent user credentials.
-   */
-  export interface Credentials {
-    name: string;
-    pass: string;
+  if (!match) {
+    return undefined;
   }
 
-  export interface IncomingMessageLike {
-    headers?: {
-      authorization?: string;
-    };
-  }
-
-  /**
-   * Parse basic auth to object.
-   *
-   * @param {string} string
-   * @return {object}
-   * @public
-   */
-
-  export function parse(string: string): auth.Credentials | undefined {
-    if (typeof string !== 'string') {
-      return undefined;
-    }
+  // decode user pass
+  const userPass = USER_PASS_REGEXP.exec(decodeBase64(match[1]));
 
-    // parse header
-    const match = CREDENTIALS_REGEXP.exec(string);
-
-    if (!match) {
-      return undefined;
-    }
-
-    // decode user pass
-    const userPass = USER_PASS_REGEXP.exec(decodeBase64(match[1]));
-
-    if (!userPass) {
-      return undefined;
-    }
-
-    // return credentials object
-    return new CredentialsImpl(userPass[1], userPass[2]);
+  if (!userPass) {
+    return undefined;
   }
+
+  // return credentials object
+  return new CredentialsImpl(userPass[1], userPass[2]);
 }
 
 /**
@@ -110,20 +79,7 @@ function decodeBase64(str: string): string {
   return Buffer.from(str, 'base64').toString();
 }
 
-/**
- * Get the Authorization header from request object.
- * @private
- */
-
-function getAuthorization(req: auth.IncomingMessageLike) {
-  if (!req.headers || typeof req.headers !== 'object') {
-    throw new TypeError('argument req is required to have headers property');
-  }
-
-  return req.headers.authorization;
-}
-
-class CredentialsImpl implements auth.Credentials {
+class CredentialsImpl implements Credentials {
   name: string;
   pass: string;
 
diff --git a/src/parse.spec.ts b/src/parse.spec.ts
index 06edfbf..4f3f692 100644
--- a/src/parse.spec.ts
+++ b/src/parse.spec.ts
@@ -1,42 +1,34 @@
 import { describe, it, assert } from 'vitest';
-import auth from './index';
+import { parse } from './index';
 
-function request(authorization: string) {
-  return {
-    headers: {
-      authorization: authorization,
-    },
-  };
-}
-
-describe('auth.parse(string)', function () {
+describe('parse(string)', function () {
   describe('with undefined string', function () {
     it('should return undefined', function () {
-      assert.strictEqual((auth as any).parse(), undefined);
+      assert.strictEqual((parse as any)(), undefined);
     });
   });
 
   describe('with malformed string', function () {
     it('should return undefined', function () {
-      assert.strictEqual(auth.parse('Something'), undefined);
+      assert.strictEqual(parse('Something'), undefined);
     });
   });
 
   describe('with malformed scheme', function () {
     it('should return undefined', function () {
-      assert.strictEqual(auth.parse('basic_Zm9vOmJhcg=='), undefined);
+      assert.strictEqual(parse('basic_Zm9vOmJhcg=='), undefined);
     });
   });
 
   describe('with malformed credentials', function () {
     it('should return undefined', function () {
-      assert.strictEqual(auth.parse('basic Zm9vcgo='), undefined);
+      assert.strictEqual(parse('basic Zm9vcgo='), undefined);
     });
   });
 
   describe('with valid credentials', function () {
     it('should return .name and .pass', function () {
-      var creds = auth.parse('basic Zm9vOmJhcg==');
+      var creds = parse('basic Zm9vOmJhcg==');
       assert.strictEqual(creds?.name, 'foo');
       assert.strictEqual(creds?.pass, 'bar');
     });
@@ -44,7 +36,7 @@ describe('auth.parse(string)', function () {
 
   describe('with empty password', function () {
     it('should return .name and .pass', function () {
-      var creds = auth.parse('basic Zm9vOg==');
+      var creds = parse('basic Zm9vOg==');
       assert.strictEqual(creds?.name, 'foo');
       assert.strictEqual(creds?.pass, '');
     });
@@ -52,7 +44,7 @@ describe('auth.parse(string)', function () {
 
   describe('with empty userid', function () {
     it('should return .name and .pass', function () {
-      var creds = auth.parse('basic OnBhc3M=');
+      var creds = parse('basic OnBhc3M=');
       assert.strictEqual(creds?.name, '');
       assert.strictEqual(creds?.pass, 'pass');
     });
@@ -60,7 +52,7 @@ describe('auth.parse(string)', function () {
 
   describe('with empty userid and pass', function () {
     it('should return .name and .pass', function () {
-      var creds = auth.parse('basic Og==');
+      var creds = parse('basic Og==');
       assert.strictEqual(creds?.name, '');
       assert.strictEqual(creds?.pass, '');
     });
@@ -68,7 +60,7 @@ describe('auth.parse(string)', function () {
 
   describe('with colon in pass', function () {
     it('should return .name and .pass', function () {
-      var creds = auth.parse('basic Zm9vOnBhc3M6d29yZA==');
+      var creds = parse('basic Zm9vOnBhc3M6d29yZA==');
       assert.strictEqual(creds?.name, 'foo');
       assert.strictEqual(creds?.pass, 'pass:word');
     });
@@ -76,8 +68,7 @@ describe('auth.parse(string)', function () {
 
   describe('with scheme "Basic"', function () {
     it('should return .name and .pass', function () {
-      var req = request('Basic Zm9vOmJhcg==');
-      var creds = auth(req);
+      var creds = parse('Basic Zm9vOmJhcg==');
       assert.strictEqual(creds?.name, 'foo');
       assert.strictEqual(creds?.pass, 'bar');
     });
@@ -85,8 +76,7 @@ describe('auth.parse(string)', function () {
 
   describe('with scheme "BASIC"', function () {
     it('should return .name and .pass', function () {
-      var req = request('BASIC Zm9vOmJhcg==');
-      var creds = auth(req);
+      var creds = parse('BASIC Zm9vOmJhcg==');
       assert.strictEqual(creds?.name, 'foo');
       assert.strictEqual(creds?.pass, 'bar');
     });
@@ -94,8 +84,7 @@ describe('auth.parse(string)', function () {
 
   describe('with scheme "BaSiC"', function () {
     it('should return .name and .pass', function () {
-      var req = request('BaSiC Zm9vOmJhcg==');
-      var creds = auth(req);
+      var creds = parse('BaSiC Zm9vOmJhcg==');
       assert.strictEqual(creds?.name, 'foo');
       assert.strictEqual(creds?.pass, 'bar');
     });