diff --git a/bin/cli-flags.js b/bin/cli-flags.js
index 0f62ab15d7..c23d102024 100644
--- a/bin/cli-flags.js
+++ b/bin/cli-flags.js
@@ -16,11 +16,18 @@ module.exports = {
     },
     {
       name: 'port',
-      type: Number,
+      type: [Number, String],
       configs: [
         {
           type: 'number',
         },
+        {
+          type: 'string',
+        },
+        {
+          type: 'enum',
+          values: ['auto'],
+        },
       ],
       description: 'The port server will listen to.',
     },
diff --git a/test/cli/__snapshots__/cli.test.js.snap.webpack4 b/test/cli/__snapshots__/cli.test.js.snap.webpack4
index fe1971d386..a1fc9be2f2 100644
--- a/test/cli/__snapshots__/cli.test.js.snap.webpack4
+++ b/test/cli/__snapshots__/cli.test.js.snap.webpack4
@@ -164,6 +164,23 @@ exports[`CLI --no-https-request-cert 1`] = `
 <i> [webpack-dev-server] Content not from webpack is served from '<cwd>/public' directory"
 `;
 
+exports[`CLI --port is auto: stderr 1`] = `
+"<i> [webpack-dev-server] Project is running at:
+<i> [webpack-dev-server] Loopback: http://localhost:<port>/
+<i> [webpack-dev-server] On Your Network (IPv4): http://<network-ip-v4>:<port>/
+<i> [webpack-dev-server] On Your Network (IPv6): http://[<network-ip-v6>]:<port>/
+<i> [webpack-dev-server] Content not from webpack is served from '<cwd>/public' directory"
+`;
+
+exports[`CLI --port is string: stderr 1`] = `
+"<w> [webpack-dev-server] The \\"port\\" specified in options is different from the port passed as an argument. Will be used from arguments.
+<i> [webpack-dev-server] Project is running at:
+<i> [webpack-dev-server] Loopback: http://localhost:<port>/
+<i> [webpack-dev-server] On Your Network (IPv4): http://<network-ip-v4>:<port>/
+<i> [webpack-dev-server] On Your Network (IPv6): http://[<network-ip-v6>]:<port>/
+<i> [webpack-dev-server] Content not from webpack is served from '<cwd>/public' directory"
+`;
+
 exports[`CLI https and other related options 1`] = `
 "<i> [webpack-dev-server] Project is running at:
 <i> [webpack-dev-server] Loopback: https://localhost:<port>/
diff --git a/test/cli/__snapshots__/cli.test.js.snap.webpack5 b/test/cli/__snapshots__/cli.test.js.snap.webpack5
index 7ce3811dce..539e62098b 100644
--- a/test/cli/__snapshots__/cli.test.js.snap.webpack5
+++ b/test/cli/__snapshots__/cli.test.js.snap.webpack5
@@ -164,6 +164,23 @@ exports[`CLI --no-https-request-cert 1`] = `
 <i> [webpack-dev-server] Content not from webpack is served from '<cwd>/public' directory"
 `;
 
+exports[`CLI --port is auto: stderr 1`] = `
+"<i> [webpack-dev-server] Project is running at:
+<i> [webpack-dev-server] Loopback: http://localhost:<port>/
+<i> [webpack-dev-server] On Your Network (IPv4): http://<network-ip-v4>:<port>/
+<i> [webpack-dev-server] On Your Network (IPv6): http://[<network-ip-v6>]:<port>/
+<i> [webpack-dev-server] Content not from webpack is served from '<cwd>/public' directory"
+`;
+
+exports[`CLI --port is string: stderr 1`] = `
+"<w> [webpack-dev-server] The \\"port\\" specified in options is different from the port passed as an argument. Will be used from arguments.
+<i> [webpack-dev-server] Project is running at:
+<i> [webpack-dev-server] Loopback: http://localhost:<port>/
+<i> [webpack-dev-server] On Your Network (IPv4): http://<network-ip-v4>:<port>/
+<i> [webpack-dev-server] On Your Network (IPv6): http://[<network-ip-v6>]:<port>/
+<i> [webpack-dev-server] Content not from webpack is served from '<cwd>/public' directory"
+`;
+
 exports[`CLI https and other related options 1`] = `
 "<i> [webpack-dev-server] Project is running at:
 <i> [webpack-dev-server] Loopback: https://localhost:<port>/
diff --git a/test/cli/cli.test.js b/test/cli/cli.test.js
index 7cede8787a..af3796c17f 100644
--- a/test/cli/cli.test.js
+++ b/test/cli/cli.test.js
@@ -432,6 +432,32 @@ describe('CLI', () => {
       .catch(done);
   });
 
+  it('--port is string', (done) => {
+    testBin(`--port "8080"`)
+      .then((output) => {
+        expect(output.exitCode).toEqual(0);
+        expect(normalizeStderr(output.stderr, { ipv6: true })).toMatchSnapshot(
+          'stderr'
+        );
+
+        done();
+      })
+      .catch(done);
+  });
+
+  it(`--port is auto`, (done) => {
+    testBin(`--port auto`)
+      .then((output) => {
+        expect(output.exitCode).toEqual(0);
+        expect(normalizeStderr(output.stderr, { ipv6: true })).toMatchSnapshot(
+          'stderr'
+        );
+
+        done();
+      })
+      .catch(done);
+  });
+
   it('--open', (done) => {
     testBin('--open')
       .then((output) => {