diff --git a/lib/application.js b/lib/application.js
index 601728a..013724d 100644
--- a/lib/application.js
+++ b/lib/application.js
@@ -13,6 +13,7 @@ var Cookies = require('cookies');
 var accepts = require('accepts');
 var assert = require('assert');
 var http = require('http');
+var only = require('only');
 var co = require('co');
 
 /**
@@ -68,6 +69,22 @@ app.listen = function(){
   return server.listen.apply(server, arguments);
 };
 
+/**
+ * Return JSON representation.
+ *
+ * @return {Object}
+ * @api public
+ */
+
+app.toJSON = function(){
+  return only(this, [
+    'outputErrors',
+    'subdomainOffset',
+    'poweredBy',
+    'env'
+  ]);
+};
+
 /**
  * Use the given middleware `fn`.
  *
@@ -197,4 +214,4 @@ function *respond(next){
   this.length = Buffer.byteLength(body);
   if (head) return res.end();
   res.end(body);
-}
+}
\ No newline at end of file
diff --git a/package.json b/package.json
index bea995e..72c192c 100644
--- a/package.json
+++ b/package.json
@@ -30,7 +30,8 @@
     "fresh": "~0.2.1",
     "koa-compose": "~2.2.0",
     "cookies": "~0.4.0",
-    "delegates": "0.0.3"
+    "delegates": "0.0.3",
+    "only": "0.0.2"
   },
   "devDependencies": {
     "should": "~3.1.0",
diff --git a/test/application.js b/test/application.js
index 478b348..f2c56df 100644
--- a/test/application.js
+++ b/test/application.js
@@ -47,6 +47,20 @@ describe('app', function(){
   })
 })
 
+describe('app.toJSON()', function(){
+  it('should work', function(){
+    var app = koa();
+    var obj = app.toJSON();
+
+    obj.should.eql({
+      outputErrors: false,
+      subdomainOffset: 2,
+      poweredBy: true,
+      env: 'test'
+    });
+  })
+})
+
 describe('app.use(fn)', function(){
   it('should compose middleware', function(done){
     var app = koa();