diff --git a/README.md b/README.md
index 1f830de..19f907c 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,22 @@ get "/" do |env|
 end
 ```
 
+### accumulated entries
+
+When `basic_auth` is called in several times, the credentials are accumulated and shared by all pages.
+
+```crystal
+basic_auth "user1", "123"
+get "/members" do |env|
+  "restricted page" # both `user1` and `guest` can see this page.
+end
+
+basic_auth "guest", "temp"
+get "/trial" do |env|
+  "restricted page" # both `user1` and `guest` can see this page.
+end
+```
+
 ## Contributing
 
 1. Fork it ( https://github.com/kemalcr/kemal-basic-auth/fork )
diff --git a/spec/credentials_spec.cr b/spec/credentials_spec.cr
index b9f05cc..f58b1a6 100644
--- a/spec/credentials_spec.cr
+++ b/spec/credentials_spec.cr
@@ -6,12 +6,35 @@ describe "HTTPBasicAuth::Credentials" do
       "serdar"   => "123",
       "dogruyol" => "abc",
     }
-    crendentials = HTTPBasicAuth::Credentials.new(entries)
+    credentials = HTTPBasicAuth::Credentials.new(entries)
 
-    crendentials.authorize?("serdar"  , "123").should eq("serdar")
-    crendentials.authorize?("serdar"  , "xxx").should eq(nil)
-    crendentials.authorize?("dogruyol", "abc").should eq("dogruyol")
-    crendentials.authorize?("dogruyol", "xxx").should eq(nil)
-    crendentials.authorize?("foo"     , "bar").should eq(nil)
+    credentials.authorize?("serdar"  , "123").should eq("serdar")
+    credentials.authorize?("serdar"  , "xxx").should eq(nil)
+    credentials.authorize?("dogruyol", "abc").should eq("dogruyol")
+    credentials.authorize?("dogruyol", "xxx").should eq(nil)
+    credentials.authorize?("foo"     , "bar").should eq(nil)
+  end
+
+  describe "#update" do
+    credentials = HTTPBasicAuth::Credentials.new
+
+    it "(String, String) adds a new entry" do
+      credentials.authorize?("serdar", "123").should eq(nil)
+      credentials.update("serdar", "123")
+      credentials.authorize?("serdar", "123").should eq("serdar")
+      credentials.authorize?("serdar", "xxx").should eq(nil)
+    end
+
+    it "(Hash) adds new entries" do
+      credentials.update({"a" => "1", "b" => "2"})
+      credentials.authorize?("a", "1").should eq("a")
+      credentials.authorize?("a", "x").should eq(nil)
+      credentials.authorize?("b", "2").should eq("b")
+      credentials.authorize?("c", "3").should eq(nil)
+    end
+
+    it "preserves accumulated entries" do
+      credentials.authorize?("serdar", "123").should eq("serdar")
+    end
   end
 end
diff --git a/spec/kemal-basic-auth_spec.cr b/spec/kemal-basic-auth_spec.cr
index 95d1ab3..882e282 100644
--- a/spec/kemal-basic-auth_spec.cr
+++ b/spec/kemal-basic-auth_spec.cr
@@ -28,8 +28,23 @@ describe "HTTPBasicAuth" do
     context.kemal_authorized_username?.should eq(nil)
   end
 
-  it "adds HTTPBasicAuthHandler" do
+  it "adds HTTPBasicAuthHandler at most once" do
     basic_auth "serdar", "123"
     Kemal.config.handlers.size.should eq 6
+
+    basic_auth "dogruyol", "abc"
+    Kemal.config.handlers.size.should eq 6
+  end
+
+  describe ".runtime" do
+    it "returns singleton instance" do
+      HTTPBasicAuth.runtime.should be_a(HTTPBasicAuth)
+    end
+
+    it "is affected by `basic_auth`" do
+      HTTPBasicAuth.runtime.authorize?("a", "1").should eq(nil)
+      basic_auth "a", "1"
+      HTTPBasicAuth.runtime.authorize?("a", "1").should eq("a")
+    end
   end
 end
diff --git a/src/kemal-basic-auth.cr b/src/kemal-basic-auth.cr
index 785ec51..d2cfe0f 100644
--- a/src/kemal-basic-auth.cr
+++ b/src/kemal-basic-auth.cr
@@ -20,7 +20,17 @@ class HTTPBasicAuth
   AUTH_MESSAGE          = "Could not verify your access level for that URL.\nYou have to login with proper credentials"
   HEADER_LOGIN_REQUIRED = "Basic realm=\"Login Required\""
 
-  def initialize(@credentials : Credentials)
+  # a lazy singleton instance which is automatically added to handler in first access
+  @@runtime : self?
+  def self.runtime
+    @@runtime ||= new.tap{|handler| add_handler handler}
+    @@runtime.not_nil!
+  end
+
+  getter credentials
+  delegate update, to: credentials
+
+  def initialize(@credentials : Credentials = Credentials.new)
   end
 
   # backward compatibility
@@ -51,15 +61,19 @@ class HTTPBasicAuth
 
   def authorize?(value) : String?
     username, password = Base64.decode_string(value[BASIC.size + 1..-1]).split(":")
+    authorize?(username, password)
+  end
+
+  def authorize?(username : String, password : String) : String?
     @credentials.authorize?(username, password)
   end
 end
 
 # Helper to easily add HTTP Basic Auth support.
 def basic_auth(username, password)
-  add_handler HTTPBasicAuth.new(username, password)
+  HTTPBasicAuth.runtime.update(username, password)
 end
 
 def basic_auth(crendentials : Hash(String, String))
-  add_handler HTTPBasicAuth.new(crendentials)
+  HTTPBasicAuth.runtime.update(crendentials)
 end
diff --git a/src/kemal-basic-auth/credentials.cr b/src/kemal-basic-auth/credentials.cr
index 405ae1e..7996191 100644
--- a/src/kemal-basic-auth/credentials.cr
+++ b/src/kemal-basic-auth/credentials.cr
@@ -1,6 +1,8 @@
-class HTTPBasicAuth
+class HTTPBasicAuth 
   class Credentials
-    def initialize(@entries : Hash(String, String) = Hash(String, String).new)
+    alias Entries = Hash(String, String)
+
+    def initialize(@entries : Entries = Entries.new)
     end
 
     def authorize?(username : String, password : String) : String?
@@ -10,5 +12,13 @@ class HTTPBasicAuth
         nil
       end
     end
+
+    def update(username : String, password : String)
+      @entries[username] = password
+    end
+
+    def update(other : Entries)
+      @entries.merge!(other)
+    end
   end
 end