diff --git a/internal/updater/updater.go b/internal/updater/updater.go
index ece7c81..38ad63d 100644
--- a/internal/updater/updater.go
+++ b/internal/updater/updater.go
@@ -1,4 +1,4 @@
-// Package updater runs one dynamic DNS update pass across all configured entries.
+// Package updater runs dynamic DNS update passes across all configured entries.
 package updater
 
 import (
@@ -11,11 +11,28 @@ import (
 	"git.aehoo.net/alphard/he-dydns/internal/network"
 )
 
-// Run discovers the current address(es) and updates every configured entry.
-// It returns an error only when address discovery itself fails outright;
-// per-entry update failures are logged and aggregated but do not stop other
-// entries from being attempted.
-func Run(cfg *config.Config) error {
+type cacheKey struct {
+	hostname   string
+	recordType config.RecordType
+}
+
+// Updater runs update passes and remembers the last address successfully
+// published for each entry, so unchanged addresses aren't re-sent upstream.
+type Updater struct {
+	last map[cacheKey]net.IP
+}
+
+// New returns an Updater with no cached state; its first Run always
+// publishes every entry that has a usable address.
+func New() *Updater {
+	return &Updater{last: make(map[cacheKey]net.IP)}
+}
+
+// Run discovers the current address(es) and updates entries whose address
+// changed since the last successful update. It returns an error only when
+// address discovery itself fails outright; per-entry update failures are
+// logged and aggregated but do not stop other entries from being attempted.
+func (u *Updater) Run(cfg *config.Config) error {
 	addrs, err := network.Discover(cfg.Interface)
 	if err != nil {
 		return fmt.Errorf("discovering address: %w", err)
@@ -48,12 +65,20 @@ func Run(cfg *config.Config) error {
 			continue
 		}
 
+		key := cacheKey{hostname: entry.Hostname, recordType: entry.RecordType}
+		if last, ok := u.last[key]; ok && last.Equal(ip) {
+			log.Printf("%s (%s) unchanged at %s; skipping update", entry.Hostname, entry.RecordType, ip)
+			continue
+		}
+
 		if err := hedns.Update(entry.Hostname, entry.Token, ip); err != nil {
 			log.Printf("error: %v", err)
 			failures++
-		} else {
-			log.Printf("updated %s (%s) -> %s", entry.Hostname, entry.RecordType, ip)
+			continue
 		}
+
+		log.Printf("updated %s (%s) -> %s", entry.Hostname, entry.RecordType, ip)
+		u.last[key] = ip
 	}
 
 	if failures > 0 {
diff --git a/main.go b/main.go
index b8e686c..b8622a5 100644
--- a/main.go
+++ b/main.go
@@ -61,7 +61,9 @@ func main() {
 		log.Fatalf("fatal: %v", err)
 	}
 
-	runErr := updater.Run(cfg)
+	u := updater.New()
+
+	runErr := u.Run(cfg)
 	if runErr != nil {
 		log.Printf("update pass completed with errors: %v", runErr)
 	}
@@ -85,7 +87,7 @@ func main() {
 	for {
 		select {
 		case <-ticker.C:
-			if err := updater.Run(cfg); err != nil {
+			if err := u.Run(cfg); err != nil {
 				log.Printf("update pass completed with errors: %v", err)
 			}
 		case sig := <-sigCh: