diff --git a/internal/app/data.go b/internal/app/data.go
index 30db8d10..137490b8 100644
--- a/internal/app/data.go
+++ b/internal/app/data.go
@@ -9,6 +9,7 @@ import (
 	"time"
 
 	"github.com/yandex/mysync/internal/mysql"
+	"github.com/yandex/mysync/internal/mysql/gtids"
 )
 
 type appState string
@@ -128,6 +129,19 @@ func (ns *NodeState) IsReplicationPermanentlyBroken() (bool, int) {
 	return false, 0
 }
 
+func (ns *NodeState) CalcGTIDDiffWithMaster() (string, error) {
+	if ns.SlaveState == nil {
+		return "", fmt.Errorf("slave state not defined")
+	}
+	replicaGTID := gtids.ParseGtidSet(ns.SlaveState.ExecutedGtidSet)
+	if ns.MasterState == nil {
+		return "", fmt.Errorf("master state not defined")
+	}
+	sourceGTID := gtids.ParseGtidSet(ns.MasterState.ExecutedGtidSet)
+
+	return gtids.GTIDDiff(replicaGTID, sourceGTID)
+}
+
 func (ns *NodeState) String() string {
 	ping := "ok"
 	if !ns.PingOk {
@@ -140,17 +154,21 @@ func (ns *NodeState) String() string {
 	repl := unknown
 	gtid := unknown
 	lag := 0.0
-	if ns.MasterState != nil {
-		repl = "master"
-		gtid = strings.ReplaceAll(ns.MasterState.ExecutedGtidSet, "\n", "")
-	} else if ns.SlaveState != nil {
+	if ns.SlaveState != nil {
 		repl = ns.SlaveState.ReplicationState
-		gtid = strings.ReplaceAll(ns.SlaveState.ExecutedGtidSet, "\n", "")
+		var err error
+		gtid, err = ns.CalcGTIDDiffWithMaster()
+		if err != nil {
+			gtid = fmt.Sprintf("%s", err)
+		}
 		if ns.SlaveState.ReplicationLag != nil {
 			lag = *ns.SlaveState.ReplicationLag
 		} else {
 			lag = math.NaN()
 		}
+	} else if ns.MasterState != nil {
+		repl = "master"
+		gtid = strings.ReplaceAll(ns.MasterState.ExecutedGtidSet, "\n", "")
 	}
 	sync := unknown
 	if ns.SemiSyncState != nil {
diff --git a/internal/app/util.go b/internal/app/util.go
index 3e878b98..2ffc2b5d 100644
--- a/internal/app/util.go
+++ b/internal/app/util.go
@@ -220,6 +220,15 @@ func getNodeStatesInParallel(hosts []string, getter func(string) (*NodeState, er
 	if err != nil {
 		return nil, err
 	}
+
+	// adding information about source to each replica
+	for host := range clusterState {
+		if clusterState[host].SlaveState == nil {
+			continue
+		}
+		masterHost := clusterState[host].SlaveState.MasterHost
+		clusterState[host].MasterState = clusterState[masterHost].MasterState
+	}
 	return clusterState, nil
 }
 
diff --git a/internal/mysql/gtids/wrapper.go b/internal/mysql/gtids/wrapper.go
index 8933d6a7..919e64eb 100644
--- a/internal/mysql/gtids/wrapper.go
+++ b/internal/mysql/gtids/wrapper.go
@@ -1,6 +1,8 @@
 package gtids
 
 import (
+	"fmt"
+
 	"github.com/go-mysql-org/go-mysql/mysql"
 )
 
@@ -13,3 +15,39 @@ func ParseGtidSet(gtidset string) mysql.GTIDSet {
 	}
 	return parsed
 }
+
+func GTIDDiff(replicaGTIDSet, sourceGTIDSet mysql.GTIDSet) (string, error) {
+	mysqlReplicaGTIDSet := replicaGTIDSet.(*mysql.MysqlGTIDSet)
+	mysqlSourceGTIDSet := sourceGTIDSet.(*mysql.MysqlGTIDSet)
+	// check standard case
+	diffWithSource := mysqlSourceGTIDSet.Clone().(*mysql.MysqlGTIDSet)
+	err := diffWithSource.Minus(*mysqlReplicaGTIDSet)
+	if err != nil {
+		return "", err
+	}
+
+	// check reverse case
+	diffWithReplica := mysqlReplicaGTIDSet.Clone().(*mysql.MysqlGTIDSet)
+	err = diffWithReplica.Minus(*mysqlSourceGTIDSet)
+	if err != nil {
+		return "", err
+	}
+
+	if diffWithSource.String() == "" && diffWithReplica.String() == "" {
+		return "replica gtid equal source", nil
+	}
+
+	if diffWithSource.String() != "" && diffWithReplica.String() == "" {
+		return fmt.Sprintf("source ahead on: %s", diffWithSource.String()), nil
+	}
+
+	if diffWithSource.String() != "" && diffWithReplica.String() != "" {
+		return fmt.Sprintf("split brain! source ahead on: %s; replica ahead on: %s", diffWithSource.String(), diffWithReplica.String()), nil
+	}
+
+	if diffWithSource.String() == "" && diffWithReplica.String() != "" {
+		return fmt.Sprintf("replica ahead on: %s", diffWithReplica.String()), nil
+	}
+
+	return "", fmt.Errorf("an indefinite case was obtained")
+}
diff --git a/internal/mysql/gtids/wrapper_test.go b/internal/mysql/gtids/wrapper_test.go
new file mode 100644
index 00000000..3c2b372e
--- /dev/null
+++ b/internal/mysql/gtids/wrapper_test.go
@@ -0,0 +1,50 @@
+package gtids
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestGTIDDiff(t *testing.T) {
+	sourceGTID := ParseGtidSet("00000000-0000-0000-0000-000000000000:1-100,11111111-1111-1111-1111-111111111111:1-100")
+
+	// equal
+	replicaGTID := ParseGtidSet("00000000-0000-0000-0000-000000000000:1-100,11111111-1111-1111-1111-111111111111:1-100")
+	diff, err := GTIDDiff(replicaGTID, sourceGTID)
+	require.NoError(t, err)
+	require.Equal(t, "replica gtid equal source", diff)
+
+	replicaGTID = ParseGtidSet("11111111-1111-1111-1111-111111111111:1-100,00000000-0000-0000-0000-000000000000:1-100")
+	diff, err = GTIDDiff(replicaGTID, sourceGTID)
+	require.NoError(t, err)
+	require.Equal(t, "replica gtid equal source", diff)
+
+	// source ahead
+	replicaGTID = ParseGtidSet("00000000-0000-0000-0000-000000000000:1-90,11111111-1111-1111-1111-111111111111:1-100")
+	diff, err = GTIDDiff(replicaGTID, sourceGTID)
+	require.NoError(t, err)
+	require.Equal(t, "source ahead on: 00000000-0000-0000-0000-000000000000:91-100", diff)
+
+	replicaGTID = ParseGtidSet("00000000-0000-0000-0000-000000000000:1-90,11111111-1111-1111-1111-111111111111:1-90")
+	diff, err = GTIDDiff(replicaGTID, sourceGTID)
+	require.NoError(t, err)
+	require.Equal(t, "source ahead on: 00000000-0000-0000-0000-000000000000:91-100,11111111-1111-1111-1111-111111111111:91-100", diff)
+
+	// replica ahead
+	replicaGTID = ParseGtidSet("00000000-0000-0000-0000-000000000000:1-110,11111111-1111-1111-1111-111111111111:1-100")
+	diff, err = GTIDDiff(replicaGTID, sourceGTID)
+	require.NoError(t, err)
+	require.Equal(t, "replica ahead on: 00000000-0000-0000-0000-000000000000:101-110", diff)
+
+	// split brain
+	replicaGTID = ParseGtidSet("00000000-0000-0000-0000-000000000000:1-90,11111111-1111-1111-1111-111111111111:1-110")
+	diff, err = GTIDDiff(replicaGTID, sourceGTID)
+	require.NoError(t, err)
+	require.Equal(t, "split brain! source ahead on: 00000000-0000-0000-0000-000000000000:91-100; replica ahead on: 11111111-1111-1111-1111-111111111111:101-110", diff)
+
+	replicaGTID = ParseGtidSet("00000000-0000-0000-0000-000000000000:1-100,22222222-2222-2222-2222-222222222222:1-110")
+	diff, err = GTIDDiff(replicaGTID, sourceGTID)
+	require.NoError(t, err)
+	require.Equal(t, "split brain! source ahead on: 11111111-1111-1111-1111-111111111111:1-100; replica ahead on: 22222222-2222-2222-2222-222222222222:1-110", diff)
+}