diff --git a/__tests__/registries/npm-registry.js b/__tests__/registries/npm-registry.js
index 6fa85aac66..ce0f97e464 100644
--- a/__tests__/registries/npm-registry.js
+++ b/__tests__/registries/npm-registry.js
@@ -72,138 +72,504 @@ function createMocks(): Object {
 }
 
 describe('request', () => {
-  test('should call requestManager.request with url', () => {
+  // a helper function for creating an instance of npm registry,
+  // making requests and inspecting request parameters
+  function createRegistry(config: Object): Object {
     const testCwd = '.';
     const {mockRequestManager, mockRegistries, mockReporter} = createMocks();
     const npmRegistry = new NpmRegistry(testCwd, mockRegistries, mockRequestManager, mockReporter);
+    npmRegistry.config = config;
+    return {
+      request(url: string, options: Object, packageName: string): Object {
+        npmRegistry.request(url, options, packageName);
+        const lastIndex = mockRequestManager.request.mock.calls.length - 1;
+        const requestParams = mockRequestManager.request.mock.calls[lastIndex][0];
+        return requestParams;
+      },
+    };
+  }
 
+  test('should call requestManager.request with url', () => {
     const url = 'https://github.com/yarnpkg/yarn.tgz';
-
-    npmRegistry.request(url);
-
-    const requestParams = mockRequestManager.request.mock.calls[0][0];
-
+    const config = {};
+    const requestParams = createRegistry(config).request(url);
     expect(requestParams.url).toBe(url);
   });
 
-  test('should not add authorization header if pathname not to registry', () => {
-    const testCwd = '.';
-    const {mockRequestManager, mockRegistries, mockReporter} = createMocks();
-    const npmRegistry = new NpmRegistry(testCwd, mockRegistries, mockRequestManager, mockReporter);
-
-    const url = 'https://github.com/yarnpkg/yarn.tgz';
-
-    npmRegistry.request(url);
-
-    const requestParams = mockRequestManager.request.mock.calls[0][0];
-
-    expect(requestParams.headers.authorization).toBeUndefined();
-  });
-
-  test('should not add authorization header if pathname not to registry and always-auth is true', () => {
-    const testCwd = '.';
-    const {mockRequestManager, mockRegistries, mockReporter} = createMocks();
-    const npmRegistry = new NpmRegistry(testCwd, mockRegistries, mockRequestManager, mockReporter);
-
-    const url = 'https://github.com/yarnpkg/yarn.tgz';
-
-    npmRegistry.config = {
-      'always-auth': true,
-      _authToken: 'testAuthToken',
-    };
-    npmRegistry.request(url);
-
-    const requestParams = mockRequestManager.request.mock.calls[0][0];
-
-    expect(requestParams.headers.authorization).toBeUndefined();
-  });
-
-  test('should not add authorization header if pathname is to registry and always-auth is false', () => {
-    const testCwd = '.';
-    const {mockRequestManager, mockRegistries, mockReporter} = createMocks();
-    const npmRegistry = new NpmRegistry(testCwd, mockRegistries, mockRequestManager, mockReporter);
-
-    const url = 'https://registry.npmjs.org/yarnpkg/yarn.tgz';
-
-    npmRegistry.config = {
-      // Default is: 'always-auth': false,
-      _authToken: 'testAuthToken',
-    };
-    npmRegistry.request(url);
-
-    const requestParams = mockRequestManager.request.mock.calls[0][0];
-
-    expect(requestParams.headers.authorization).toBeUndefined();
-  });
-
-  test('should not add authorization header if pathname is to registry and not scopped package', () => {
-    const testCwd = '.';
-    const {mockRequestManager, mockRegistries, mockReporter} = createMocks();
-    const npmRegistry = new NpmRegistry(testCwd, mockRegistries, mockRequestManager, mockReporter);
-
-    const url = 'https://registry.npmjs.org/yarnpkg/yarn.tgz';
-
-    npmRegistry.config = {
-      _authToken: 'testAuthToken',
-    };
-    npmRegistry.request(url);
-
-    const requestParams = mockRequestManager.request.mock.calls[0][0];
-
-    expect(requestParams.headers.authorization).toBeUndefined();
-  });
-
-  test('should add authorization header if pathname is to registry and always-auth is true', () => {
-    const testCwd = '.';
-    const {mockRequestManager, mockRegistries, mockReporter} = createMocks();
-    const npmRegistry = new NpmRegistry(testCwd, mockRegistries, mockRequestManager, mockReporter);
-
-    const url = 'https://registry.npmjs.org/yarnpkg/yarn.tgz';
-
-    npmRegistry.config = {
-      'always-auth': true,
-      _authToken: 'testAuthToken',
-    };
-    npmRegistry.request(url);
-
-    const requestParams = mockRequestManager.request.mock.calls[0][0];
-
-    expect(requestParams.headers.authorization).toBe('Bearer testAuthToken');
-  });
-
-  test('should add authorization header if pathname is to registry and is scopped package', () => {
-    const testCwd = '.';
-    const {mockRequestManager, mockRegistries, mockReporter} = createMocks();
-    const npmRegistry = new NpmRegistry(testCwd, mockRegistries, mockRequestManager, mockReporter);
-
-    const url = 'https://registry.npmjs.org/@testScope%2fyarn.tgz';
-
-    npmRegistry.config = {
-      _authToken: 'testAuthToken',
-    };
-    npmRegistry.request(url);
-
-    const requestParams = mockRequestManager.request.mock.calls[0][0];
-
-    expect(requestParams.headers.authorization).toBe('Bearer testAuthToken');
-  });
-
-  test('should add authorization header with token for custom registries with a scoped package', () => {
-    const testCwd = '.';
-    const {mockRequestManager, mockRegistries, mockReporter} = createMocks();
-    const npmRegistry = new NpmRegistry(testCwd, mockRegistries, mockRequestManager, mockReporter);
-
-    const url = 'https://some.other.registry/@testScope%2fyarn.tgz';
-
-    npmRegistry.config = {
-      '//some.other.registry/:_authToken': 'testScopedAuthToken',
-      '@testScope:registry': '//some.other.registry/',
-    };
-    npmRegistry.request(url);
-
-    const requestParams = mockRequestManager.request.mock.calls[0][0];
-
-    expect(requestParams.headers.authorization).toBe('Bearer testScopedAuthToken');
+  const testCases = [
+    {
+      title: 'using npm as default registry and using private registry for scoped packages',
+      config: {
+        '//registry.myorg.com/:_authToken': 'scopedPrivateAuthToken',
+        '@private:registry': 'https://registry.myorg.com/',
+      },
+      requests: [
+        {
+          url: 'yarn',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: '@yarn%2fcore',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: '-/package/yarn/dist-tags',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: '-/package/@yarn%2fcore/dist-tags',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: '-/user/token/abcdef',
+          pkg: null,
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: 'https://registry.npmjs.org/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.yarnpkg.com', auth: false},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: null,
+          expect: {root: 'https://registry.yarnpkg.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: '@private/pkg',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com', auth: 'scopedPrivateAuthToken'},
+        },
+        {
+          url: 'https://some.cdn.com/some-hash/@private-pkg-1.0.0.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@private/pkg',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+      ],
+    },
+    {
+      title: 'using scoped packages in both npm and private registry',
+      config: {
+        '//registry.npmjs.org/:_authToken': 'scopedNpmAuthToken',
+        '@yarn:registry': 'https://registry.npmjs.org/',
+        '//registry.myorg.com/:_authToken': 'scopedPrivateAuthToken',
+        '@private:registry': 'https://registry.myorg.com/',
+      },
+      requests: [
+        {
+          url: 'yarn',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: '@yarn%2fcore',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: '-/package/yarn/dist-tags',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: '-/package/@yarn%2fcore/dist-tags',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: '-/user/token/abcdef',
+          pkg: null,
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: 'https://registry.npmjs.org/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.yarnpkg.com', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: null,
+          expect: {root: 'https://registry.yarnpkg.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: '@private/pkg',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com', auth: 'scopedPrivateAuthToken'},
+        },
+        {
+          url: 'https://some.cdn.com/some-hash/@private-pkg-1.0.0.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@private/pkg',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+      ],
+    },
+    {
+      title: 'using authenticated npm and using private registry for scoped packages',
+      config: {
+        _authToken: 'scopedNpmAuthToken',
+        '//registry.myorg.com/:_authToken': 'scopedPrivateAuthToken',
+        '@private:registry': 'https://registry.myorg.com/',
+      },
+      requests: [
+        {
+          url: 'yarn',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: '@yarn%2fcore',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: '-/package/yarn/dist-tags',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: '-/package/@yarn%2fcore/dist-tags',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: '-/user/token/abcdef',
+          pkg: null,
+          expect: {root: 'https://registry.npmjs.org', auth: false},
+        },
+        {
+          url: 'https://registry.npmjs.org/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.yarnpkg.com', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: null,
+          expect: {root: 'https://registry.yarnpkg.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: '@private/pkg',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com', auth: 'scopedPrivateAuthToken'},
+        },
+        {
+          url: 'https://some.cdn.com/some-hash/@private-pkg-1.0.0.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@private/pkg',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+      ],
+    },
+    {
+      title: 'using npm with always-auth and using private registry for scoped packages',
+      config: {
+        'always-auth': true,
+        '//registry.npmjs.org/:_authToken': 'npmAuthToken',
+        '@private:registry': 'https://registry.myorg.com/',
+        '//registry.myorg.com/:_authToken': 'scopedPrivateAuthToken',
+      },
+      requests: [
+        {
+          url: 'yarn',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.npmjs.org', auth: 'npmAuthToken'},
+        },
+        {
+          url: '@yarn%2fcore',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'npmAuthToken'},
+        },
+        {
+          url: '-/package/yarn/dist-tags',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.npmjs.org', auth: 'npmAuthToken'},
+        },
+        {
+          url: '-/package/@yarn%2fcore/dist-tags',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'npmAuthToken'},
+        },
+        {
+          url: '-/user/token/abcdef',
+          pkg: null,
+          expect: {root: 'https://registry.npmjs.org', auth: 'npmAuthToken'},
+        },
+        {
+          url: 'https://registry.npmjs.org/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'npmAuthToken'},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.yarnpkg.com', auth: 'npmAuthToken'},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: null,
+          expect: {root: 'https://registry.yarnpkg.com', auth: 'npmAuthToken'},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: '@private/pkg',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com', auth: 'scopedPrivateAuthToken'},
+        },
+        {
+          url: 'https://some.cdn.com/some-hash/@private-pkg-1.0.0.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@private/pkg',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+      ],
+    },
+    {
+      title: 'using private registry as default registry and using scoped packages on npm registry',
+      config: {
+        'always-auth': true,
+        registry: 'https://registry.myorg.com/',
+        '//registry.myorg.com/:_authToken': 'privateAuthToken',
+        '//registry.npmjs.org/:_authToken': 'scopedNpmAuthToken',
+        '@yarn:registry': 'https://registry.npmjs.org/',
+      },
+      requests: [
+        {
+          url: 'yarn',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.myorg.com', auth: 'privateAuthToken'},
+        },
+        {
+          url: '@yarn%2fcore',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: '-/package/yarn/dist-tags',
+          pkg: 'yarn',
+          expect: {root: 'https://registry.myorg.com', auth: 'privateAuthToken'},
+        },
+        {
+          url: '-/package/@yarn%2fcore/dist-tags',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: '-/user/token/abcdef',
+          pkg: null,
+          expect: {root: 'https://registry.myorg.com', auth: 'privateAuthToken'},
+        },
+        {
+          url: 'https://registry.npmjs.org/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.npmjs.org', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://registry.yarnpkg.com', auth: 'scopedNpmAuthToken'},
+        },
+        {
+          url: 'https://registry.yarnpkg.com/dist/-/@yarn-core-1.0.0.tgz',
+          pkg: null,
+          expect: {root: 'https://registry.yarnpkg.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: '@yarn/core',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@yarn/core.tgz',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: '@private/pkg',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com', auth: 'privateAuthToken'},
+        },
+        {
+          url: 'https://some.cdn.com/some-hash/@private-pkg-1.0.0.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@private/pkg',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+      ],
+    },
+    {
+      title: 'registry url and request url path sensitivity',
+      config: {
+        '@private:registry': 'https://registry.myorg.com/api/npm/registry/',
+        '//registry.myorg.com/api/npm/registry/:_authToken': 'scopedPrivateAuthToken',
+      },
+      requests: [
+        {
+          url: 'https://registry.myorg.com/api/npm/registry/private---pkg.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com/api/npm/registry/', auth: 'scopedPrivateAuthToken'},
+        },
+        {
+          url: 'https://registry.myorg.com/api/packages/private---pkg.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com/api/packages/', auth: false},
+        },
+      ],
+    },
+    {
+      title: 'using custom-host-suffix for registries where pathnames play a role',
+      config: {
+        '@private:registry': 'https://registry.myorg.com/api/npm/registry/',
+        '//registry.myorg.com/api/npm/registry/:_authToken': 'scopedPrivateAuthToken',
+        'custom-host-suffix': 'registry.myorg.com',
+      },
+      requests: [
+        {
+          url: '@private/pkg',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com/api/npm/registry/', auth: 'scopedPrivateAuthToken'},
+        },
+        {
+          url: 'https://some.cdn.com/some-hash/@private-pkg-1.0.0.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@private/pkg',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://registry.myorg.com/api/packages/private---pkg.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com/api/packages/', auth: 'scopedPrivateAuthToken'},
+        },
+      ],
+    },
+    {
+      title: 'using multiple config entries for registries where pathnames play a role',
+      config: {
+        '@private:registry': 'https://registry.myorg.com/api/npm/registry/',
+        '//registry.myorg.com/api/npm/registry/:_authToken': 'scopedPrivateAuthToken',
+        '//registry.myorg.com/api/packages/:_authToken': 'scopedPrivateAuthToken',
+      },
+      requests: [
+        {
+          url: '@private/pkg',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com/api/npm/registry/', auth: 'scopedPrivateAuthToken'},
+        },
+        {
+          url: 'https://some.cdn.com/some-hash/@private-pkg-1.0.0.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://some.cdn.com/@private/pkg',
+          pkg: null,
+          expect: {root: 'https://some.cdn.com', auth: false},
+        },
+        {
+          url: 'https://registry.myorg.com/api/packages/private---pkg.tar.gz',
+          pkg: '@private/pkg',
+          expect: {root: 'https://registry.myorg.com/api/packages/', auth: 'scopedPrivateAuthToken'},
+        },
+      ],
+    },
+  ];
+
+  testCases.forEach(testCase => {
+    describe(testCase.title, () => {
+      const registry = createRegistry(testCase.config);
+      testCase.requests.forEach(req => {
+        const desc =
+          `with request url ${req.url}${req.pkg ? ` in context of package ${req.pkg}` : ''} ` +
+          `auth is ${req.expect.auth ? req.expect.auth : 'not sent'}`;
+        (req.skip ? it.skip : req.only ? it.only : it)(desc, () => {
+          const requestParams = registry.request(req.url, {}, req.pkg);
+          expect(requestParams.url.substr(0, req.expect.root.length)).toBe(req.expect.root);
+          expect(requestParams.headers.authorization).toBe(req.expect.auth ? `Bearer ${req.expect.auth}` : undefined);
+        });
+      });
+    });
   });
 });
 
@@ -222,6 +588,9 @@ describe('isRequestToRegistry functional test', () => {
       ['http://foo.bar/foo/bar/baz', 'https://foo.bar:443/foo/'],
       ['https://foo.bar/foo/bar/baz', 'https://foo.bar:443/foo/'],
       ['HTTP://xn--xample-hva.com:80/foo/bar/baz', 'http://êxample.com/foo/bar/baz'],
+      // yarn and npm registries are interchangeable
+      ['https://registry.npmjs.org/foo/bar', 'https://registry.npmjs.org/'],
+      ['https://registry.yarnpkg.com/foo/bar', 'https://registry.npmjs.org/'],
     ];
 
     const invalidRegistryUrls = [
diff --git a/src/registries/npm-registry.js b/src/registries/npm-registry.js
index 501ef18a48..3a553d1131 100644
--- a/src/registries/npm-registry.js
+++ b/src/registries/npm-registry.js
@@ -72,6 +72,19 @@ function normalizePath(val: mixed): ?string {
   return resolveWithHome(val);
 }
 
+type UrlParts = {
+  host: string,
+  path: string,
+};
+
+function urlParts(requestUrl: string): UrlParts {
+  const normalizedUrl = normalizeUrl(requestUrl);
+  const parsed = url.parse(normalizedUrl);
+  const host = parsed.host || '';
+  const path = parsed.path || '';
+  return {host, path};
+}
+
 export default class NpmRegistry extends Registry {
   constructor(cwd: string, registries: ConfigRegistries, requestManager: RequestManager, reporter: Reporter) {
     super(cwd, registries, requestManager, reporter);
@@ -100,21 +113,18 @@ export default class NpmRegistry extends Registry {
   }
 
   isRequestToRegistry(requestUrl: string, registryUrl: string): boolean {
-    const normalizedRequestUrl = normalizeUrl(requestUrl);
-    const normalizedRegistryUrl = normalizeUrl(registryUrl);
-    const requestParsed = url.parse(normalizedRequestUrl);
-    const registryParsed = url.parse(normalizedRegistryUrl);
-    const requestHost = requestParsed.host || '';
-    const registryHost = registryParsed.host || '';
-    const requestPath = requestParsed.path || '';
-    const registryPath = registryParsed.path || '';
+    const request = urlParts(requestUrl);
+    const registry = urlParts(registryUrl);
     const customHostSuffix = this.getRegistryOrGlobalOption(registryUrl, 'custom-host-suffix');
 
+    const requestToRegistryHost = () => request.host === registry.host;
+    const requestToYarn = () => YARN_REGISTRY.includes(request.host) && DEFAULT_REGISTRY.includes(registry.host);
+
     return (
-      requestHost === registryHost &&
-      (requestPath.startsWith(registryPath) ||
+      (requestToRegistryHost() || requestToYarn()) &&
+      (request.path.startsWith(registry.path) ||
         // For some registries, the package path does not prefix with the registry path
-        (typeof customHostSuffix === 'string' && requestHost.endsWith(customHostSuffix)))
+        (typeof customHostSuffix === 'string' && request.host.endsWith(customHostSuffix)))
     );
   }
 
@@ -133,7 +143,7 @@ export default class NpmRegistry extends Registry {
       opts.headers,
     );
 
-    const isToRegistry = this.isRequestToRegistry(requestUrl, registry);
+    const isToRegistry = this.isRequestToRegistry(requestUrl, registry) || this.requestNeedsAuth(requestUrl);
 
     // this.token must be checked to account for publish requests on non-scopped packages
     if (this.token || (isToRegistry && (alwaysAuth || this.isScopedPackage(packageIdent)))) {
@@ -156,6 +166,21 @@ export default class NpmRegistry extends Registry {
     });
   }
 
+  requestNeedsAuth(requestUrl: string): boolean {
+    const config = this.config;
+    const requestParts = urlParts(requestUrl);
+    return !!Object.keys(config).find(option => {
+      const parts = option.split(':');
+      if (parts.length === 2 && parts[1] === '_authToken') {
+        const registryParts = urlParts(parts[0]);
+        if (requestParts.host === registryParts.host && requestParts.path.startsWith(registryParts.path)) {
+          return true;
+        }
+      }
+      return false;
+    });
+  }
+
   async checkOutdated(config: Config, name: string, range: string): CheckOutdatedReturn {
     const req = await this.request(NpmRegistry.escapeName(name), {
       headers: {Accept: 'application/json'},