diff --git a/doc/doxygen/main_page.h b/doc/doxygen/main_page.h
index 4b2ccba4..d70d8348 100644
--- a/doc/doxygen/main_page.h
+++ b/doc/doxygen/main_page.h
@@ -1,3 +1,13 @@
+/**
+ * @defgroup callbackstyle_api Callback-style APIs
+ * Non thread-safe APIs, callback style for maximum performance and minimum
+ * memory footprint.
+ * 
+ * @defgroup threadsafe_api Thread-safe APIs
+ * Thread-safe APIs, blocking functions. More overhead, but can be called
+ * from any thread except TCPIP thread.
+ */
+
 /*! \mainpage lwIP Documentation
  *
  * \section intro_sec Introduction
diff --git a/src/api/api_lib.c b/src/api/api_lib.c
index 03f083dd..778cacb4 100644
--- a/src/api/api_lib.c
+++ b/src/api/api_lib.c
@@ -36,6 +36,7 @@
 
 /**
  * @defgroup netconn Netconn API
+ * @ingroup threadsafe_api
  * Thread-safe, to be called from non-TCPIP threads only.
  * TX/RX handling based on @ref netbuf (containing @ref pbuf)
  * to avoid copying data around.
@@ -115,7 +116,6 @@ netconn_apimsg(tcpip_callback_fn fn, struct api_msg *apimsg)
 }
 
 /**
- * @ingroup netconn_common
  * Create a new netconn (of a specific type) that has a callback function.
  * The corresponding pcb is also created.
  *
diff --git a/src/api/netifapi.c b/src/api/netifapi.c
index 9b1c048e..3a02d521 100644
--- a/src/api/netifapi.c
+++ b/src/api/netifapi.c
@@ -33,6 +33,7 @@
 
 /**
  * @defgroup netifapi NETIF API
+ * @ingroup threadsafe_api
  * Thread-safe functions to be called from non-TCPIP threads
  * 
  * @defgroup netifapi_netif NETIF related
diff --git a/src/api/sockets.c b/src/api/sockets.c
index e0b072fe..6547182c 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -40,6 +40,7 @@
 
 /**
  * @defgroup socket Socket API
+ * @ingroup threadsafe_api
  * BSD-style socket API.\n
  * Thread-safe, to be called from non-TCPIP threads only.\n
  * Can be activated by defining LWIP_SOCKET to 1.\n
diff --git a/src/api/tcpip.c b/src/api/tcpip.c
index 60452737..32abf5f8 100644
--- a/src/api/tcpip.c
+++ b/src/api/tcpip.c
@@ -441,6 +441,7 @@ tcpip_trycallback(struct tcpip_callback_msg* msg)
 }
 
 /**
+ * @ingroup lwIP
  * Initialize this module:
  * - initialize all sub modules
  * - start the tcpip_thread
diff --git a/src/core/dns.c b/src/core/dns.c
index 5ee482ce..75cf12ee 100644
--- a/src/core/dns.c
+++ b/src/core/dns.c
@@ -39,6 +39,7 @@
 
 /**
  * @defgroup dns DNS
+ * @ingroup callbackstyle_api
  *
  * Implements a DNS host name to IP address resolver.
  *
diff --git a/src/core/init.c b/src/core/init.c
index 96aa02c7..3cf504f4 100644
--- a/src/core/init.c
+++ b/src/core/init.c
@@ -323,6 +323,7 @@
 /**
  * @ingroup lwIP
  * Initialize all modules.
+ * Use this in NO_SYS mode. Use tcpip_init() otherwise.
  */
 void
 lwip_init(void)
diff --git a/src/core/ip.c b/src/core/ip.c
index af6e36b3..4a36da18 100644
--- a/src/core/ip.c
+++ b/src/core/ip.c
@@ -38,8 +38,10 @@
 
 /**
  * @defgroup ip4 IPv4
+ * @ingroup callbackstyle_api
  *
  * @defgroup ip6 IPv6
+ * @ingroup callbackstyle_api
  * 
  * @defgroup ipaddr IP address handling
  * 
diff --git a/src/core/netif.c b/src/core/netif.c
index 7d368e9f..1281fa63 100644
--- a/src/core/netif.c
+++ b/src/core/netif.c
@@ -36,6 +36,7 @@
 
 /**
  * @defgroup netif Network interface (NETIF)
+ * @ingroup callbackstyle_api
  */
 
 #include "lwip/opt.h"
diff --git a/src/core/raw.c b/src/core/raw.c
index 8747353f..90f2e302 100644
--- a/src/core/raw.c
+++ b/src/core/raw.c
@@ -40,6 +40,7 @@
 
 /**
  * @defgroup raw_api RAW API
+ * @ingroup callbackstyle_api
  * @verbinclude "rawapi.txt"
  */
 
diff --git a/src/include/lwip/api.h b/src/include/lwip/api.h
index a919a2d1..bbe45713 100644
--- a/src/include/lwip/api.h
+++ b/src/include/lwip/api.h
@@ -257,7 +257,6 @@ struct netconn {
 
 /** @ingroup netconn_common */
 #define netconn_new(t)                  netconn_new_with_proto_and_callback(t, 0, NULL)
-/** @ingroup netconn_common */
 #define netconn_new_with_callback(t, c) netconn_new_with_proto_and_callback(t, 0, c)
 struct netconn *netconn_new_with_proto_and_callback(enum netconn_type t, u8_t proto,
                                              netconn_callback callback);