diff --git a/src/Config.py b/src/Config.py
index 6bd44974..4fd29a02 100644
--- a/src/Config.py
+++ b/src/Config.py
@@ -8,7 +8,7 @@ class Config(object):
 
     def __init__(self, argv):
         self.version = "0.3.2"
-        self.rev = 467
+        self.rev = 470
         self.argv = argv
         self.action = None
         self.createParser()
diff --git a/src/Content/ContentManager.py b/src/Content/ContentManager.py
index 094a11b2..abcec3ce 100644
--- a/src/Content/ContentManager.py
+++ b/src/Content/ContentManager.py
@@ -10,6 +10,8 @@ from Debug import Debug
 from Crypt import CryptHash
 from Config import config
 from util import helper
+from Peer import PeerHashfield
+
 
 class ContentManager(object):
 
@@ -17,6 +19,8 @@ class ContentManager(object):
         self.site = site
         self.log = self.site.log
         self.contents = {}  # Known content.json (without files and includes)
+        self.hashfield = PeerHashfield()
+        self.site.onFileDone.append(lambda inner_path: self.addOptionalFile(inner_path))
         self.loadContent(add_bad_files=False, delete_removed_files=False)
         self.site.settings["size"] = self.getTotalSize()
 
@@ -302,7 +306,9 @@ class ContentManager(object):
         self.log.info("Opening site data directory: %s..." % directory)
 
         changed_files = [inner_path]
-        files_node, files_optional_node = self.hashFiles(helper.getDirname(inner_path), content.get("ignore"), content.get("optional"))
+        files_node, files_optional_node = self.hashFiles(
+            helper.getDirname(inner_path), content.get("ignore"), content.get("optional")
+        )
 
         # Find changed files
         files_merged = files_node.copy()
@@ -459,7 +465,9 @@ class ContentManager(object):
 
         if rules.get("max_size_optional") is not None:  # Include optional files limit
             if content_size_optional > rules["max_size_optional"]:
-                self.log.error("%s: Include optional files too large %s > %s" % (inner_path, content_size_optional, rules["max_size_optional"]))
+                self.log.error("%s: Include optional files too large %s > %s" % (
+                    inner_path, content_size_optional, rules["max_size_optional"])
+                )
                 return False
 
         # Filename limit
@@ -567,6 +575,12 @@ class ContentManager(object):
                 self.log.error("File not in content.json: %s" % inner_path)
                 return False
 
+    def addOptionalFile(self, inner_path):
+        info = self.getFileInfo(inner_path)
+        if info and info["optional"]:
+            self.log.debug("Downloaded optional file, adding to hashfield: %s" % inner_path)
+            self.hashfield.appendHash(info["sha512"])
+
 
 if __name__ == "__main__":
     def testSign():
diff --git a/src/File/FileRequest.py b/src/File/FileRequest.py
index 71586aa1..23d90334 100644
--- a/src/File/FileRequest.py
+++ b/src/File/FileRequest.py
@@ -65,6 +65,8 @@ class FileRequest(object):
             self.actionPex(params)
         elif cmd == "listModified":
             self.actionListModified(params)
+        elif cmd == "getHashfield":
+            self.actionGetHashfield(params)
         elif cmd == "ping":
             self.actionPing()
         else:
@@ -257,6 +259,20 @@ class FileRequest(object):
 
         self.response({"modified_files": modified_files})
 
+    def actionGetHashfield(self, params):
+        site = self.sites.get(params["site"])
+        if not site or not site.settings["serving"]:  # Site unknown or not serving
+            self.response({"error": "Unknown site"})
+            return False
+
+        # Add peer to site if not added before
+        connected_peer = site.addPeer(self.connection.ip, self.connection.port)
+        if connected_peer:  # Just added
+            connected_peer.connect(self.connection)  # Assign current connection to peer
+
+        self.response({"hashfield_raw": site.content_manager.hashfield.tostring()})
+
+
     # Send a simple Pong! answer
     def actionPing(self):
         self.response("Pong!")
diff --git a/src/Peer/Peer.py b/src/Peer/Peer.py
index af3ca228..a0f65005 100644
--- a/src/Peer/Peer.py
+++ b/src/Peer/Peer.py
@@ -8,6 +8,7 @@ from cStringIO import StringIO
 from Debug import Debug
 from Config import config
 from util import helper
+from PeerHashfield import PeerHashfield
 
 if config.use_tempfiles:
     import tempfile
@@ -27,8 +28,8 @@ class Peer(object):
         self.key = "%s:%s" % (ip, port)
 
         self.connection = None
-        self.hashfield = array.array("H")  # Got optional files hash_id
-        self.last_hashfield = None  # Last time hashfiled downloaded
+        self.hashfield = PeerHashfield()  # Got optional files hash_id
+        self.last_hashfield = 0  # Last time hashfiled downloaded
         self.last_found = time.time()  # Time of last found in the torrent tracker
         self.last_response = None  # Time of last successful response from peer
         self.last_ping = None  # Last response time for ping
@@ -221,6 +222,16 @@ class Peer(object):
             self.log("Added peers using pex: %s" % added)
         return added
 
+    # Request optional files hashfield from peer
+    def getHashfield(self):
+        self.last_hashfield = time.time()
+        res = self.request("getHashfield", {"site": self.site.address})
+        if res and "error" not in res:
+            self.hashfield.replaceFromString(res["hashfield_raw"])
+            return self.hashfield
+        else:
+            return False
+
     # List modified files since the date
     # Return: {inner_path: modification date,...}
     def listModified(self, since):
diff --git a/src/Peer/PeerHashfield.py b/src/Peer/PeerHashfield.py
new file mode 100644
index 00000000..593932d3
--- /dev/null
+++ b/src/Peer/PeerHashfield.py
@@ -0,0 +1,42 @@
+import array
+
+
+class PeerHashfield():
+    def __init__(self):
+        self.storage = self.createStoreage()
+
+    def createStoreage(self):
+        storage = array.array("H")
+        self.append = storage.append
+        self.remove = storage.remove
+        self.tostring = storage.tostring
+        self.fromstring = storage.fromstring
+        self.__len__ = storage.__len__
+        self.__iter__ = storage.__iter__
+        return storage
+
+    def appendHash(self, hash):
+        hash_id = int(hash[0:4], 16)
+        if hash_id not in self:
+            self.append(hash_id)
+            return True
+        else:
+            return False
+
+    def removeHash(self, hash):
+        hash_id = int(hash[0:4], 16)
+        if hash_id in self:
+            self.remove(hash_id)
+            return True
+        else:
+            return False
+
+    def getHashId(self, hash):
+        return int(hash[0:4], 16)
+
+    def hasHash(self, hash):
+        return int(hash[0:4], 16) in self
+
+    def replaceFromString(self, hashfield_raw):
+        self.storage = self.createStoreage()
+        self.fromstring(hashfield_raw)
\ No newline at end of file
diff --git a/src/Peer/__init__.py b/src/Peer/__init__.py
index 82110b81..3e92827f 100644
--- a/src/Peer/__init__.py
+++ b/src/Peer/__init__.py
@@ -1 +1,2 @@
 from Peer import Peer
+from PeerHashfield import PeerHashfield
diff --git a/src/Site/Site.py b/src/Site/Site.py
index cdaad9d8..f236421e 100644
--- a/src/Site/Site.py
+++ b/src/Site/Site.py
@@ -34,6 +34,7 @@ class Site:
         self.address = re.sub("[^A-Za-z0-9]", "", address)  # Make sure its correct address
         self.address_short = "%s..%s" % (self.address[:6], self.address[-4:])  # Short address for logging
         self.log = logging.getLogger("Site:%s" % self.address_short)
+        self.addEventListeners()
 
         self.content = None  # Load content.json
         self.peers = {}  # Key: ip:port, Value: Peer.Peer
@@ -66,9 +67,6 @@ class Site:
 
         self.websockets = []  # Active site websocket connections
 
-        # Add event listeners
-        self.addEventListeners()
-
     def __str__(self):
         return "Site %s" % self.address_short
 
diff --git a/src/Site/SiteStorage.py b/src/Site/SiteStorage.py
index 5b87f306..4c78c977 100644
--- a/src/Site/SiteStorage.py
+++ b/src/Site/SiteStorage.py
@@ -218,6 +218,10 @@ class SiteStorage:
     def isFile(self, inner_path):
         return os.path.isfile(self.getPath(inner_path))
 
+    # File or directory exist
+    def isExists(self, inner_path):
+        return os.path.exists(self.getPath(inner_path))
+
     # Dir exist
     def isDir(self, inner_path):
         return os.path.isdir(self.getPath(inner_path))
@@ -246,6 +250,7 @@ class SiteStorage:
     # Verify all files sha512sum using content.json
     def verifyFiles(self, quick_check=False):  # Fast = using file size
         bad_files = []
+
         if not self.site.content_manager.contents.get("content.json"):  # No content.json, download it first
             self.site.needFile("content.json", update=True)  # Force update to fix corrupt file
             self.site.content_manager.loadContent()  # Reload content.json
@@ -253,7 +258,8 @@ class SiteStorage:
             if not os.path.isfile(self.getPath(content_inner_path)):  # Missing content.json file
                 self.log.debug("[MISSING] %s" % content_inner_path)
                 bad_files.append(content_inner_path)
-            for file_relative_path in content["files"].keys():
+
+            for file_relative_path in content.get("files", {}).keys():
                 file_inner_path = helper.getDirname(content_inner_path) + file_relative_path  # Relative to site dir
                 file_inner_path = file_inner_path.strip("/")  # Strip leading /
                 file_path = self.getPath(file_inner_path)
@@ -270,9 +276,34 @@ class SiteStorage:
                 if not ok:
                     self.log.debug("[CHANGED] %s" % file_inner_path)
                     bad_files.append(file_inner_path)
+
+            # Optional files
+            optional_added = 0
+            optional_removed = 0
+            for file_relative_path in content.get("files_optional", {}).keys():
+                file_inner_path = helper.getDirname(content_inner_path) + file_relative_path  # Relative to site dir
+                file_inner_path = file_inner_path.strip("/")  # Strip leading /
+                file_path = self.getPath(file_inner_path)
+                if not os.path.isfile(file_path):
+                    self.site.content_manager.hashfield.removeHash(content["files_optional"][file_relative_path]["sha512"])
+                    continue
+
+                if quick_check:
+                    ok = os.path.getsize(file_path) == content["files_optional"][file_relative_path]["size"]
+                else:
+                    ok = self.site.content_manager.verifyFile(file_inner_path, open(file_path, "rb"))
+
+                if ok:
+                    self.site.content_manager.hashfield.appendHash(content["files_optional"][file_relative_path]["sha512"])
+                    optional_added += 1
+                else:
+                    self.site.content_manager.hashfield.removeHash(content["files_optional"][file_relative_path]["sha512"])
+                    optional_removed += 1
+                    self.log.debug("[OPTIONAL CHANGED] %s" % file_inner_path)
+
             self.log.debug(
-                "%s verified: %s files, quick_check: %s, bad files: %s" %
-                (content_inner_path, len(content["files"]), quick_check, bad_files)
+                "%s verified: %s, quick: %s, bad: %s, optionals: +%s -%s" %
+                (content_inner_path, len(content["files"]), quick_check, bad_files, optional_added, optional_removed)
             )
 
         return bad_files
diff --git a/src/Test/TestPeer.py b/src/Test/TestPeer.py
index 5c9a7aba..ac6521d7 100644
--- a/src/Test/TestPeer.py
+++ b/src/Test/TestPeer.py
@@ -1,11 +1,9 @@
-import cStringIO as StringIO
 
 import pytest
-import time
 
-from Connection import ConnectionServer
-from Connection import Connection
 from File import FileServer
+from Crypt import CryptHash
+from cStringIO import StringIO
 
 
 @pytest.mark.usefixtures("resetSettings")
@@ -52,3 +50,47 @@ class TestFileRequest:
 
         connection.close()
         client.stop()
+
+    def testHashfield(self, site):
+        sample_hash = site.content_manager.contents["content.json"]["files_optional"].values()[0]["sha512"]
+        site.storage.verifyFiles(quick_check=True)  # Find what optional files we have
+
+        # Check if hashfield has any files
+        assert len(site.content_manager.hashfield) > 0
+
+        # Check exsist hash
+        assert site.content_manager.hashfield.getHashId(sample_hash) in site.content_manager.hashfield
+
+        # Add new hash
+        new_hash = CryptHash.sha512sum(StringIO("hello"))
+        assert site.content_manager.hashfield.getHashId(new_hash) not in site.content_manager.hashfield
+        assert site.content_manager.hashfield.appendHash(new_hash)
+        assert not site.content_manager.hashfield.appendHash(new_hash)  # Don't add second time
+        assert site.content_manager.hashfield.getHashId(new_hash) in site.content_manager.hashfield
+
+        # Remove new hash
+        assert site.content_manager.hashfield.removeHash(new_hash)
+        assert site.content_manager.hashfield.getHashId(new_hash) not in site.content_manager.hashfield
+
+    def testHashfieldExchange(self, file_server, site, site_temp):
+        file_server.ip_incoming = {}  # Reset flood protection
+        file_server.sites[site.address] = site
+        client = FileServer("127.0.0.1", 1545)
+        client.sites[site_temp.address] = site_temp
+        site_temp.connection_server = client
+        connection = client.getConnection("127.0.0.1", 1544)
+        site.storage.verifyFiles(quick_check=True)  # Find what optional files we have
+
+        # Add file_server as peer to client
+        peer_file_server = site_temp.addPeer("127.0.0.1", 1544)
+
+        # Check if hashfield has any files
+        assert len(site.content_manager.hashfield) > 0
+
+        # Testing hashfield sync
+        assert len(peer_file_server.hashfield) == 0
+        assert peer_file_server.getHashfield()
+        assert len(peer_file_server.hashfield) > 0
+
+        connection.close()
+        client.stop()
diff --git a/src/Test/TestSiteDownload.py b/src/Test/TestSiteDownload.py
index 86e5f4d8..7630f847 100644
--- a/src/Test/TestSiteDownload.py
+++ b/src/Test/TestSiteDownload.py
@@ -1,16 +1,15 @@
 import pytest
 import mock
-import time
 
 from Connection import ConnectionServer
 from Config import config
-from Site import Site
 from File import FileRequest
 import Spy
 
+
 @pytest.mark.usefixtures("resetTempSettings")
 @pytest.mark.usefixtures("resetSettings")
-class TestWorker:
+class TestSiteDownload:
     def testDownload(self, file_server, site, site_temp):
         client = ConnectionServer("127.0.0.1", 1545)
         assert site.storage.directory == config.data_dir + "/" + site.address
@@ -57,7 +56,13 @@ class TestWorker:
 
         # Optional user file
         assert not site_temp.storage.isFile("data/users/1CjfbrbwtP8Y2QjPy12vpTATkUT7oSiPQ9/peanut-butter-jelly-time.gif")
+        optional_file_info = site_temp.content_manager.getFileInfo(
+            "data/users/1CjfbrbwtP8Y2QjPy12vpTATkUT7oSiPQ9/peanut-butter-jelly-time.gif"
+        )
+        assert not site_temp.content_manager.hashfield.hasHash(optional_file_info["sha512"])
+
         site_temp.needFile("data/users/1CjfbrbwtP8Y2QjPy12vpTATkUT7oSiPQ9/peanut-butter-jelly-time.gif")
         assert site_temp.storage.isFile("data/users/1CjfbrbwtP8Y2QjPy12vpTATkUT7oSiPQ9/peanut-butter-jelly-time.gif")
+        assert site_temp.content_manager.hashfield.hasHash(optional_file_info["sha512"])
 
         assert site_temp.storage.deleteFiles()