diff --git a/src/core/mac/mac.cpp b/src/core/mac/mac.cpp
index 8bd0ae942..c4ea922fe 100644
--- a/src/core/mac/mac.cpp
+++ b/src/core/mac/mac.cpp
@@ -53,8 +53,6 @@
 #include "thread/mle_router.hpp"
 #include "thread/thread_netif.hpp"
 
-using ot::Encoding::BigEndian::HostSwap64;
-
 namespace ot {
 namespace Mac {
 
diff --git a/src/core/meshcop/energy_scan_client.cpp b/src/core/meshcop/energy_scan_client.cpp
index a1d3b6d4d..1229099f2 100644
--- a/src/core/meshcop/energy_scan_client.cpp
+++ b/src/core/meshcop/energy_scan_client.cpp
@@ -50,9 +50,6 @@
 
 #if OPENTHREAD_ENABLE_COMMISSIONER && OPENTHREAD_FTD
 
-using ot::Encoding::BigEndian::HostSwap16;
-using ot::Encoding::BigEndian::HostSwap32;
-
 namespace ot {
 
 EnergyScanClient::EnergyScanClient(Instance &aInstance)
diff --git a/src/core/meshcop/joiner_router.cpp b/src/core/meshcop/joiner_router.cpp
index 624d1456b..fc47fbde3 100644
--- a/src/core/meshcop/joiner_router.cpp
+++ b/src/core/meshcop/joiner_router.cpp
@@ -51,7 +51,6 @@
 #include "thread/thread_uri_paths.hpp"
 
 using ot::Encoding::BigEndian::HostSwap16;
-using ot::Encoding::BigEndian::HostSwap64;
 
 namespace ot {
 namespace MeshCoP {
diff --git a/src/core/net/dhcp6_client.cpp b/src/core/net/dhcp6_client.cpp
index 24d1a04f3..8e3878b2f 100644
--- a/src/core/net/dhcp6_client.cpp
+++ b/src/core/net/dhcp6_client.cpp
@@ -48,7 +48,6 @@
 #if OPENTHREAD_ENABLE_DHCP6_CLIENT
 
 using ot::Encoding::BigEndian::HostSwap16;
-using ot::Encoding::BigEndian::HostSwap32;
 
 namespace ot {
 
diff --git a/src/core/net/dhcp6_server.cpp b/src/core/net/dhcp6_server.cpp
index 6f388d740..64193d5b5 100644
--- a/src/core/net/dhcp6_server.cpp
+++ b/src/core/net/dhcp6_server.cpp
@@ -44,9 +44,6 @@
 
 #if OPENTHREAD_ENABLE_DHCP6_SERVER
 
-using ot::Encoding::BigEndian::HostSwap16;
-using ot::Encoding::BigEndian::HostSwap32;
-
 namespace ot {
 namespace Dhcp6 {
 
diff --git a/src/core/net/sntp_client.cpp b/src/core/net/sntp_client.cpp
index efd3d5785..102783c01 100644
--- a/src/core/net/sntp_client.cpp
+++ b/src/core/net/sntp_client.cpp
@@ -45,8 +45,6 @@
  *   This file implements the SNTP client.
  */
 
-using ot::Encoding::BigEndian::HostSwap16;
-
 namespace ot {
 namespace Sntp {
 
diff --git a/src/core/thread/announce_begin_server.cpp b/src/core/thread/announce_begin_server.cpp
index da2147eb5..7f3b095bf 100644
--- a/src/core/thread/announce_begin_server.cpp
+++ b/src/core/thread/announce_begin_server.cpp
@@ -47,8 +47,6 @@
 #include "thread/thread_netif.hpp"
 #include "thread/thread_uri_paths.hpp"
 
-using ot::Encoding::BigEndian::HostSwap32;
-
 namespace ot {
 
 AnnounceBeginServer::AnnounceBeginServer(Instance &aInstance)
diff --git a/src/core/thread/network_data_leader.cpp b/src/core/thread/network_data_leader.cpp
index 9ddc0e9bd..cb6557597 100644
--- a/src/core/thread/network_data_leader.cpp
+++ b/src/core/thread/network_data_leader.cpp
@@ -52,8 +52,6 @@
 #include "thread/thread_tlvs.hpp"
 #include "thread/thread_uri_paths.hpp"
 
-using ot::Encoding::BigEndian::HostSwap16;
-
 namespace ot {
 namespace NetworkData {
 
diff --git a/src/core/thread/network_diagnostic.cpp b/src/core/thread/network_diagnostic.cpp
index f5867ac49..7c41c09a2 100644
--- a/src/core/thread/network_diagnostic.cpp
+++ b/src/core/thread/network_diagnostic.cpp
@@ -52,8 +52,6 @@
 #include "thread/thread_tlvs.hpp"
 #include "thread/thread_uri_paths.hpp"
 
-using ot::Encoding::BigEndian::HostSwap16;
-
 #if OPENTHREAD_FTD || OPENTHREAD_ENABLE_MTD_NETWORK_DIAGNOSTIC
 
 namespace ot {
diff --git a/src/core/thread/thread_netif.cpp b/src/core/thread/thread_netif.cpp
index 8e29e0a27..6bcfa8fb7 100644
--- a/src/core/thread/thread_netif.cpp
+++ b/src/core/thread/thread_netif.cpp
@@ -44,8 +44,6 @@
 #include "thread/thread_tlvs.hpp"
 #include "thread/thread_uri_paths.hpp"
 
-using ot::Encoding::BigEndian::HostSwap16;
-
 namespace ot {
 
 ThreadNetif::ThreadNetif(Instance &aInstance)