diff --git a/packages/rest/package.json b/packages/rest/package.json
index 95531a46d2c1..83a0e26ca0da 100644
--- a/packages/rest/package.json
+++ b/packages/rest/package.json
@@ -25,6 +25,7 @@
   "dependencies": {
     "@loopback/context": "^0.12.5",
     "@loopback/core": "^0.11.5",
+    "@loopback/explorer": "^0.1.0",
     "@loopback/http-server": "^0.3.5",
     "@loopback/openapi-v3": "^0.12.6",
     "@loopback/openapi-v3-types": "^0.8.5",
diff --git a/packages/rest/src/rest.server.ts b/packages/rest/src/rest.server.ts
index 64258e2b30d7..2f058f611e35 100644
--- a/packages/rest/src/rest.server.ts
+++ b/packages/rest/src/rest.server.ts
@@ -38,6 +38,7 @@ import * as express from 'express';
 import {ServeStaticOptions} from 'serve-static';
 import {PathParams} from 'express-serve-static-core';
 import * as pathToRegExp from 'path-to-regexp';
+import {apiExplorerUI} from '@loopback/explorer';
 
 const debug = require('debug')('loopback:rest:server');
 
@@ -198,11 +199,25 @@ export class RestServer extends Context implements Server, HttpServerLike {
       maxAge: 86400,
       credentials: true,
     };
+    // Set up CORS
     this._expressApp.use(cors(corsOptions));
 
     // Place the assets router here before controllers
     this._setupRouterForStaticAssets();
 
+    // Serving OpenAPI spec
+    for (const p in OPENAPI_SPEC_MAPPING) {
+      this._expressApp.use(p, (req, res) =>
+        this._serveOpenApiSpec(req, res, OPENAPI_SPEC_MAPPING[p]),
+      );
+    }
+
+    // Serving API Explorer UI
+    this._expressApp.use('/api-explorer', apiExplorerUI());
+    this._expressApp.get('/swagger-ui', (req, res) =>
+      this._redirectToSwaggerUI(req, res, options),
+    );
+
     // Mount our router & request handler
     this._expressApp.use((req, res, next) => {
       this._handleHttpRequest(req, res, options!).catch(next);
@@ -232,28 +247,6 @@ export class RestServer extends Context implements Server, HttpServerLike {
     response: Response,
     options: RestServerConfig,
   ) {
-    if (
-      request.method === 'GET' &&
-      request.url &&
-      request.url in OPENAPI_SPEC_MAPPING
-    ) {
-      // NOTE(bajtos) Regular routes are handled through Sequence.
-      // IMO, this built-in endpoint should not run through a Sequence,
-      // because it's not part of the application API itself.
-      // E.g. if the app implements access/audit logs, I don't want
-      // this endpoint to trigger a log entry. If the server implements
-      // content-negotiation to support XML clients, I don't want the OpenAPI
-      // spec to be converted into an XML response.
-      const settings = OPENAPI_SPEC_MAPPING[request.url];
-      return this._serveOpenApiSpec(request, response, settings);
-    }
-    if (
-      request.method === 'GET' &&
-      request.url &&
-      request.url === '/swagger-ui'
-    ) {
-      return this._redirectToSwaggerUI(request, response, options);
-    }
     return this.httpHandler.handleRequest(request, response);
   }
 
@@ -381,11 +374,11 @@ export class RestServer extends Context implements Server, HttpServerLike {
       'http';
     let host =
       (request.get('x-forwarded-host') || '').split(',')[0] ||
-      request.headers.host!.replace(/:[0-9]+/, '');
+      request.headers.host!.replace(/:([0-9]+)$/, '');
     let port =
       (request.get('x-forwarded-port') || '').split(',')[0] ||
       options.port ||
-      (request.headers.host!.match(/:([0-9]+)/) || [])[1] ||
+      (request.headers.host!.match(/:([0-9]+)$/) || [])[1] ||
       '';
 
     // clear default ports