diff --git a/src/ddns_service/__init__.py b/src/ddns_service/__init__.py
index 1a25a1e..74d7755 100644
--- a/src/ddns_service/__init__.py
+++ b/src/ddns_service/__init__.py
@@ -10,6 +10,15 @@ import datetime
 __version__ = "1.0.0"
 __author__ = "Thomas Oettli <spacefreak@noop.ch>"
 
+# DynDNS-compatible response statuses
+STATUS_GOOD = "good"
+STATUS_NOCHG = "nochg"
+STATUS_BADAUTH = "badauth"
+STATUS_NOHOST = "nohost"
+STATUS_DNSERR = "dnserr"
+STATUS_ABUSE = "abuse"
+STATUS_BADIP = "badip"
+
 __all__ = [
     "app",
     "cleanup",
@@ -23,6 +32,13 @@ __all__ = [
     "models",
     "ratelimit",
     "server",
+    "STATUS_GOOD",
+    "STATUS_NOCHG",
+    "STATUS_BADAUTH",
+    "STATUS_NOHOST",
+    "STATUS_DNSERR",
+    "STATUS_ABUSE",
+    "STATUS_BADIP",
 ]
 
 DATETIME_FORMAT = "%Y-%m-%d %H:%M:%S %Z"
diff --git a/src/ddns_service/server.py b/src/ddns_service/server.py
index a72f126..586d539 100644
--- a/src/ddns_service/server.py
+++ b/src/ddns_service/server.py
@@ -14,7 +14,17 @@ from urllib.parse import parse_qs, urlparse
 
 import argon2
 
-from . import datetime_str, utc_now
+from . import (
+    datetime_str,
+    utc_now,
+    STATUS_GOOD,
+    STATUS_NOCHG,
+    STATUS_BADAUTH,
+    STATUS_NOHOST,
+    STATUS_DNSERR,
+    STATUS_ABUSE,
+    STATUS_BADIP,
+)
 from .cleanup import ExpiredRecordsCleanupThread, RateLimitCleanupThread
 from .logging import clear_txn_id, set_txn_id
 from .models import DoesNotExist, get_hostname_for_user, get_user
@@ -196,7 +206,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                 logging.warning(
                     f"Rate limited (bad): client={client_ip}, "
                     f"retry_at={datetime_str(retry_at)}")
-                self.respond(429, "abuse")
+                self.respond(429, STATUS_ABUSE)
                 return
 
         # Parse URL
@@ -219,7 +229,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
 
         if not username or not password:
             logging.warning(f"Auth failed: client={client_ip} user=anonymous")
-            self._handle_bad_request(client_ip, 401, "badauth")
+            self._handle_bad_request(client_ip, 401, STATUS_BADAUTH)
             return
 
         # Validate credentials
@@ -228,14 +238,14 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
             self.app.password_hasher.verify(user.password_hash, password)
         except (DoesNotExist, argon2.exceptions.VerifyMismatchError):
             logging.warning(f"Auth failed: client={client_ip} user={username}")
-            self._handle_bad_request(client_ip, 401, "badauth")
+            self._handle_bad_request(client_ip, 401, STATUS_BADAUTH)
             return
 
         # Get hostname parameter
         hostname_param = extract_param(params, endpoint["params"]["hostname"])
         if not hostname_param:
             logging.warning(f"Missing hostname: client={client_ip} user={username}")
-            self._handle_bad_request(client_ip, 400, "nohost")
+            self._handle_bad_request(client_ip, 400, STATUS_NOHOST)
             return
 
         # Validate and encode hostname
@@ -245,7 +255,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
             logging.warning(
                 f"Invalid hostname: client={client_ip}, "
                 f"hostname={hostname_param}")
-            self._handle_bad_request(client_ip, 400, "nohost")
+            self._handle_bad_request(client_ip, 400, STATUS_NOHOST)
             return
 
         # Check hostname ownership
@@ -256,7 +266,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                 f"Access denied: client={client_ip} user={username} "
                 f"hostname={hostname_param}"
             )
-            self._handle_bad_request(client_ip, 403, "nohost")
+            self._handle_bad_request(client_ip, 403, STATUS_NOHOST)
             return
 
         # Good rate limit check
@@ -266,7 +276,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                 logging.warning(
                     f"Rate limited: client={client_ip}, "
                     f"retry_at={datetime_str(retry_at)}")
-                self.respond(429, "abuse")
+                self.respond(429, STATUS_ABUSE)
                 return
 
         # Record good request
@@ -305,7 +315,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                 else:
                     ipv6 = myip
             except ValueError:
-                return (400, "badip")
+                return (400, STATUS_BADIP)
 
         # Process myip6 parameter
         if myip6:
@@ -314,9 +324,9 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                 if rtype == "AAAA":
                     ipv6 = myip6
                 else:
-                    return (400, "badip")
+                    return (400, STATUS_BADIP)
             except ValueError:
-                return (400, "badip")
+                return (400, STATUS_BADIP)
 
         # Auto-detect from client IP if no params
         if ipv4 is None and ipv6 is None:
@@ -327,7 +337,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                 else:
                     ipv6 = ip
             except ValueError:
-                return (400, "badip")
+                return (400, STATUS_BADIP)
 
         now = utc_now()
 
@@ -352,7 +362,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                         f"DNS update failed: client={client_ip} hostname={hostname.hostname} "
                         f"zone={hostname.zone} ipv4={ipv4} error={e}"
                     )
-                    return (500, "dnserr")
+                    return (500, STATUS_DNSERR)
 
         if ipv6:
             hostname.last_ipv6_update = now
@@ -373,7 +383,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                         f"DNS update failed: client={client_ip} hostname={hostname.hostname} "
                         f"zone={hostname.zone} ipv6={ipv6} error={e}"
                     )
-                    return (500, "dnserr")
+                    return (500, STATUS_DNSERR)
 
         # Update database
         hostname.save()
@@ -394,7 +404,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                 f"zone={hostname.zone}{changed_addrs} notify_change={str(notify_change).lower()}"
             )
             return (
-                200, "nochg",
+                200, STATUS_NOCHG,
                 {"ipv4": hostname.last_ipv4, "ipv6": hostname.last_ipv6}
             )
 
@@ -415,7 +425,7 @@ class DDNSRequestHandler(BaseHTTPRequestHandler):
                 logging.error(f"Sending change notification error: {e}")
 
         return (
-            200, "good",
+            200, STATUS_GOOD,
             {"ipv4": hostname.last_ipv4, "ipv6": hostname.last_ipv6}
         )