diff --git a/device/main/RFIDInterface.cpp b/device/main/RFIDInterface.cpp
index 278407f..3818345 100644
--- a/device/main/RFIDInterface.cpp
+++ b/device/main/RFIDInterface.cpp
@@ -3,15 +3,16 @@
 #include <esp_log.h>
 #include <esp_err.h>
 #include <esp_http_server.h>
+#include <stdio.h>
 
 #include "WebInterface.hpp"
 
 static const char* TAG = "rfid";
 
-void tag_handler(uint8_t* sn) { // serial number is always 5 bytes long
-    ESP_LOGI(TAG, "Tag: %#x %#x %#x %#x %#x",
-        sn[0], sn[1], sn[2], sn[3], sn[4]
-    );
+static char* lastTagId = (char*)malloc(26 * sizeof(char));
+
+static char* getLastTagId() {
+    return lastTagId;
 }
 
 RFIDInterface::RFIDInterface() {
@@ -20,7 +21,15 @@ RFIDInterface::RFIDInterface() {
         .mosi_io     = 25,
 		.sck_io      = 23,
         .sda_io      = 5,
-        .callback    = &tag_handler
+        .callback    = [](uint8_t* sn) { // serial number is always 5 bytes long
+                ESP_LOGI(TAG, "Tag: %#x %#x %#x %#x %#x",
+                    sn[0], sn[1], sn[2], sn[3], sn[4]
+                );
+
+                sprintf(lastTagId, "%#x_%#x_%#x_%#x_%#x", sn[0], sn[1], sn[2], sn[3], sn[4]);
+
+                ESP_LOGI(TAG, "sprintf tag id: %s", lastTagId);
+            }
 	};
 }
 
@@ -32,12 +41,11 @@ void RFIDInterface::registerWebResources(WebInterface* interface) {
     httpd_uri_t config = {
         .uri = "/rfid",
         .method = HTTP_GET,
-        .handler = [](httpd_req_t *req) {
-            httpd_resp_send(req, "it's all fine!", HTTPD_RESP_USE_STRLEN);
+        .handler = [](httpd_req_t *req)  {
+            httpd_resp_send(req, getLastTagId(), HTTPD_RESP_USE_STRLEN);
             return ESP_OK;
         }
     };
 
     interface->registerResource(&config);
-}
-
+}
\ No newline at end of file
diff --git a/device/main/RFIDInterface.hpp b/device/main/RFIDInterface.hpp
index 4c1bd89..a760e7d 100644
--- a/device/main/RFIDInterface.hpp
+++ b/device/main/RFIDInterface.hpp
@@ -13,4 +13,4 @@ class RFIDInterface {
 		void registerWebResources(WebInterface* interface);
 };
 
-#endif
\ No newline at end of file
+#endif	
\ No newline at end of file