diff --git a/esphome/components/web_server/__init__.py b/esphome/components/web_server/__init__.py
index 0cdf10531d..1cbc773729 100644
--- a/esphome/components/web_server/__init__.py
+++ b/esphome/components/web_server/__init__.py
@@ -351,7 +351,7 @@ async def to_code(config):
             except Exception:  # pylint: disable=broad-except
                 pass
 
-    # Generate defines for each CDN domain
+    # Generate defines for each CDN domain (used by captive_portal DNS whitelist)
     for i, domain in enumerate(sorted(cdn_domains)):
         cg.add_define(f"WEBSERVER_CDN_DOMAIN_{i}", domain)
     cg.add_define("WEBSERVER_CDN_DOMAIN_COUNT", len(cdn_domains))
diff --git a/esphome/core/progmem.h b/esphome/core/progmem.h
index d1594f47e7..fcc302e674 100644
--- a/esphome/core/progmem.h
+++ b/esphome/core/progmem.h
@@ -10,9 +10,11 @@
 #define ESPHOME_PGM_P PGM_P
 #define ESPHOME_strncpy_P strncpy_P
 #define ESPHOME_strncat_P strncat_P
+#define ESPHOME_strcasecmp_P strcasecmp_P
 #else
 #define ESPHOME_F(string_literal) (string_literal)
 #define ESPHOME_PGM_P const char *
 #define ESPHOME_strncpy_P strncpy
 #define ESPHOME_strncat_P strncat
+#define ESPHOME_strcasecmp_P strcasecmp
 #endif