diff --git a/include/tinycsocket.h b/include/tinycsocket.h
index 4857026..41e422e 100644
--- a/include/tinycsocket.h
+++ b/include/tinycsocket.h
@@ -29,7 +29,7 @@
 #ifndef TINYCSOCKET_INTERNAL_H_
 #define TINYCSOCKET_INTERNAL_H_
 
-static const char* const TCS_VERSION_TXT = "v0.3.78";
+static const char* const TCS_VERSION_TXT = "v0.3.79";
 extern const char* const TCS_LICENSE_TXT;
 
 /*
@@ -124,7 +124,7 @@ extern const char* const TCS_LICENSE_TXT;
 * - TcsResult tcs_address_socket_remote(TcsSocket socket, struct TcsAddress* out_remote_address);
 * - TcsResult tcs_address_socket_family(TcsSocket socket, TcsFamily* out_family);
 * - TcsResult tcs_address_parse(const char str[], struct TcsAddress* out_address);
-* - TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[70]);
+* - TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[], size_t str_length, size_t* out_length);
 * - bool tcs_address_is_equal(const struct TcsAddress* l, const struct TcsAddress* r);
 * - bool tcs_address_is_any(const struct TcsAddress* addr);
 * - bool tcs_address_is_link_local(const struct TcsAddress* addr);
@@ -1901,14 +1901,17 @@ TcsResult tcs_address_parse(const char str[], struct TcsAddress* out_address);
 
 /**
  * @brief Convert an address to a string.
- * 
+ *
  * This will make a verbose string representation of the address.
- * 
+ * Pass @c out_str=NULL and @c str_length=0 with @c out_length set to query the required size.
+ *
  * @param[in] address the address to convert.
- * @param[out] out_str buffer of at least 70 bytes to receive the string representation.
- * @return #TCS_SUCCESS if successful, otherwise the error code.
+ * @param[out] out_str buffer to receive the null-terminated string representation.
+ * @param[in] str_length capacity of @c out_str in bytes. A buffer of 70 bytes is always sufficient for any supported address family.
+ * @param[out] out_length receives the length of the written string excluding the null terminator. May be NULL.
+ * @return #TCS_SUCCESS if successful, #TCS_ERROR_MEMORY if @c out_str is too small, otherwise the error code.
  */
-TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[70]);
+TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[], size_t str_length, size_t* out_length);
 
 /** @brief Check if two addresses are equal. Returns false for NULL, mismatched, unknown, or unsupported address families. */
 bool tcs_address_is_equal(const struct TcsAddress* l, const struct TcsAddress* r);
@@ -7473,12 +7476,17 @@ TcsResult tcs_address_parse(const char str[], struct TcsAddress* out_address)
     return TCS_SUCCESS;
 }
 
-TcsResult tcs_address_to_str(const struct TcsAddress* address, char str[70])
+TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[], size_t str_length, size_t* out_length)
 {
-    if (address == NULL || str == NULL)
+    if (address == NULL)
+        return TCS_ERROR_INVALID_ARGUMENT;
+    if (out_str == NULL && str_length != 0)
+        return TCS_ERROR_INVALID_ARGUMENT;
+    if (out_str == NULL && out_length == NULL)
         return TCS_ERROR_INVALID_ARGUMENT;
 
-    memset(str, 0, 70);
+    char str[70];
+    memset(str, 0, sizeof str);
     if (address->family.native == TCS_FAMILY_IPV4.native)
     {
         uint32_t d = address->data.ipv4.address;
@@ -7488,9 +7496,9 @@ TcsResult tcs_address_to_str(const struct TcsAddress* address, char str[70])
         uint8_t b3 = (uint8_t)((d >> 16) & 0xFF);
         uint8_t b4 = (uint8_t)((d >> 24) & 0xFF);
         if (p == 0)
-            snprintf(str, 70, "%i.%i.%i.%i", b4, b3, b2, b1);
+            snprintf(str, sizeof str, "%i.%i.%i.%i", b4, b3, b2, b1);
         else
-            snprintf(str, 70, "%i.%i.%i.%i:%i", b4, b3, b2, b1, p);
+            snprintf(str, sizeof str, "%i.%i.%i.%i:%i", b4, b3, b2, b1, p);
     }
     else if (address->family.native == TCS_FAMILY_IPV6.native)
     {
@@ -7545,18 +7553,18 @@ TcsResult tcs_address_to_str(const struct TcsAddress* address, char str[70])
         uint16_t p = address->data.ipv6.port;
         TcsInterfaceId sc = address->data.ipv6.scope_id;
         if (p != 0 && sc != 0)
-            snprintf(str, 70, "[%s%%%u]:%u", addr_str, (unsigned int)sc, (unsigned int)p);
+            snprintf(str, sizeof str, "[%s%%%u]:%u", addr_str, (unsigned int)sc, (unsigned int)p);
         else if (p != 0)
-            snprintf(str, 70, "[%s]:%u", addr_str, (unsigned int)p);
+            snprintf(str, sizeof str, "[%s]:%u", addr_str, (unsigned int)p);
         else if (sc != 0)
-            snprintf(str, 70, "%s%%%u", addr_str, (unsigned int)sc);
+            snprintf(str, sizeof str, "%s%%%u", addr_str, (unsigned int)sc);
         else
-            snprintf(str, 70, "%s", addr_str);
+            snprintf(str, sizeof str, "%s", addr_str);
     }
     else if (address->family.native == TCS_FAMILY_PACKET.native)
     {
         snprintf(str,
-                 70,
+                 sizeof str,
                  "%02X:%02X:%02X:%02X:%02X:%02X",
                  address->data.packet.mac[0],
                  address->data.packet.mac[1],
@@ -7570,6 +7578,15 @@ TcsResult tcs_address_to_str(const struct TcsAddress* address, char str[70])
         return TCS_ERROR_NOT_IMPLEMENTED;
     }
 
+    size_t written = strlen(str);
+    if (out_length != NULL)
+        *out_length = written;
+    if (out_str == NULL)
+        return TCS_SUCCESS;
+    if (str_length <= written)
+        return TCS_ERROR_MEMORY;
+    memcpy(out_str, str, written + 1);
+
     return TCS_SUCCESS;
 }
 
diff --git a/src/tinycsocket_common.c b/src/tinycsocket_common.c
index e1e416e..cf7c221 100644
--- a/src/tinycsocket_common.c
+++ b/src/tinycsocket_common.c
@@ -1311,12 +1311,17 @@ TcsResult tcs_address_parse(const char str[], struct TcsAddress* out_address)
     return TCS_SUCCESS;
 }
 
-TcsResult tcs_address_to_str(const struct TcsAddress* address, char str[70])
+TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[], size_t str_length, size_t* out_length)
 {
-    if (address == NULL || str == NULL)
+    if (address == NULL)
+        return TCS_ERROR_INVALID_ARGUMENT;
+    if (out_str == NULL && str_length != 0)
+        return TCS_ERROR_INVALID_ARGUMENT;
+    if (out_str == NULL && out_length == NULL)
         return TCS_ERROR_INVALID_ARGUMENT;
 
-    memset(str, 0, 70);
+    char str[70];
+    memset(str, 0, sizeof str);
     if (address->family.native == TCS_FAMILY_IPV4.native)
     {
         uint32_t d = address->data.ipv4.address;
@@ -1326,9 +1331,9 @@ TcsResult tcs_address_to_str(const struct TcsAddress* address, char str[70])
         uint8_t b3 = (uint8_t)((d >> 16) & 0xFF);
         uint8_t b4 = (uint8_t)((d >> 24) & 0xFF);
         if (p == 0)
-            snprintf(str, 70, "%i.%i.%i.%i", b4, b3, b2, b1);
+            snprintf(str, sizeof str, "%i.%i.%i.%i", b4, b3, b2, b1);
         else
-            snprintf(str, 70, "%i.%i.%i.%i:%i", b4, b3, b2, b1, p);
+            snprintf(str, sizeof str, "%i.%i.%i.%i:%i", b4, b3, b2, b1, p);
     }
     else if (address->family.native == TCS_FAMILY_IPV6.native)
     {
@@ -1383,18 +1388,18 @@ TcsResult tcs_address_to_str(const struct TcsAddress* address, char str[70])
         uint16_t p = address->data.ipv6.port;
         TcsInterfaceId sc = address->data.ipv6.scope_id;
         if (p != 0 && sc != 0)
-            snprintf(str, 70, "[%s%%%u]:%u", addr_str, (unsigned int)sc, (unsigned int)p);
+            snprintf(str, sizeof str, "[%s%%%u]:%u", addr_str, (unsigned int)sc, (unsigned int)p);
         else if (p != 0)
-            snprintf(str, 70, "[%s]:%u", addr_str, (unsigned int)p);
+            snprintf(str, sizeof str, "[%s]:%u", addr_str, (unsigned int)p);
         else if (sc != 0)
-            snprintf(str, 70, "%s%%%u", addr_str, (unsigned int)sc);
+            snprintf(str, sizeof str, "%s%%%u", addr_str, (unsigned int)sc);
         else
-            snprintf(str, 70, "%s", addr_str);
+            snprintf(str, sizeof str, "%s", addr_str);
     }
     else if (address->family.native == TCS_FAMILY_PACKET.native)
     {
         snprintf(str,
-                 70,
+                 sizeof str,
                  "%02X:%02X:%02X:%02X:%02X:%02X",
                  address->data.packet.mac[0],
                  address->data.packet.mac[1],
@@ -1408,6 +1413,15 @@ TcsResult tcs_address_to_str(const struct TcsAddress* address, char str[70])
         return TCS_ERROR_NOT_IMPLEMENTED;
     }
 
+    size_t written = strlen(str);
+    if (out_length != NULL)
+        *out_length = written;
+    if (out_str == NULL)
+        return TCS_SUCCESS;
+    if (str_length <= written)
+        return TCS_ERROR_MEMORY;
+    memcpy(out_str, str, written + 1);
+
     return TCS_SUCCESS;
 }
 
diff --git a/src/tinycsocket_internal.h b/src/tinycsocket_internal.h
index bd949d3..e2882a7 100644
--- a/src/tinycsocket_internal.h
+++ b/src/tinycsocket_internal.h
@@ -23,7 +23,7 @@
 #ifndef TINYCSOCKET_INTERNAL_H_
 #define TINYCSOCKET_INTERNAL_H_
 
-static const char* const TCS_VERSION_TXT = "v0.3.78";
+static const char* const TCS_VERSION_TXT = "v0.3.79";
 extern const char* const TCS_LICENSE_TXT;
 
 /*
@@ -118,7 +118,7 @@ extern const char* const TCS_LICENSE_TXT;
 * - TcsResult tcs_address_socket_remote(TcsSocket socket, struct TcsAddress* out_remote_address);
 * - TcsResult tcs_address_socket_family(TcsSocket socket, TcsFamily* out_family);
 * - TcsResult tcs_address_parse(const char str[], struct TcsAddress* out_address);
-* - TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[70]);
+* - TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[], size_t str_length, size_t* out_length);
 * - bool tcs_address_is_equal(const struct TcsAddress* l, const struct TcsAddress* r);
 * - bool tcs_address_is_any(const struct TcsAddress* addr);
 * - bool tcs_address_is_link_local(const struct TcsAddress* addr);
@@ -1895,14 +1895,17 @@ TcsResult tcs_address_parse(const char str[], struct TcsAddress* out_address);
 
 /**
  * @brief Convert an address to a string.
- * 
+ *
  * This will make a verbose string representation of the address.
- * 
+ * Pass @c out_str=NULL and @c str_length=0 with @c out_length set to query the required size.
+ *
  * @param[in] address the address to convert.
- * @param[out] out_str buffer of at least 70 bytes to receive the string representation.
- * @return #TCS_SUCCESS if successful, otherwise the error code.
+ * @param[out] out_str buffer to receive the null-terminated string representation.
+ * @param[in] str_length capacity of @c out_str in bytes. A buffer of 70 bytes is always sufficient for any supported address family.
+ * @param[out] out_length receives the length of the written string excluding the null terminator. May be NULL.
+ * @return #TCS_SUCCESS if successful, #TCS_ERROR_MEMORY if @c out_str is too small, otherwise the error code.
  */
-TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[70]);
+TcsResult tcs_address_to_str(const struct TcsAddress* address, char out_str[], size_t str_length, size_t* out_length);
 
 /** @brief Check if two addresses are equal. Returns false for NULL, mismatched, unknown, or unsupported address families. */
 bool tcs_address_is_equal(const struct TcsAddress* l, const struct TcsAddress* r);
diff --git a/tests/tests.cpp b/tests/tests.cpp
index 6f50a30..595f598 100644
--- a/tests/tests.cpp
+++ b/tests/tests.cpp
@@ -1128,7 +1128,7 @@ TEST_CASE("Interface list")
         for (size_t j = 0; j < addr_display; ++j)
         {
             char addr_str[70];
-            tcs_address_to_str(&addresses[j].address, addr_str);
+            tcs_address_to_str(&addresses[j].address, addr_str, sizeof addr_str, NULL);
             printf("  Address %u,%zu: %s\n", interfaces[i].id, j, addr_str);
         }
     }
@@ -1158,7 +1158,7 @@ TEST_CASE("Get loopback address")
             ifaddrs[i].address.data.ipv4.address == TCS_ADDRESS_IPV4_LOOPBACK)
         {
             char out_str[70];
-            tcs_address_to_str(&ifaddrs[i].address, out_str);
+            tcs_address_to_str(&ifaddrs[i].address, out_str, sizeof out_str, NULL);
             printf("Interface loopback: %u; %s; %s\n", ifaddrs[i].iface.id, ifaddrs[i].iface.name, out_str);
             found_loopback = true;
         }
@@ -1183,7 +1183,7 @@ TEST_CASE("tcs_util_address_to_string with only IPv4")
 
     // When
     char address_str[70];
-    tcs_address_to_str(&addr, address_str);
+    tcs_address_to_str(&addr, address_str, sizeof address_str, NULL);
 
     // Then
     CHECK_EQ(address_str, "127.0.0.1");
@@ -1199,7 +1199,7 @@ TEST_CASE("tcs_util_address_to_string with IPv4 and port")
 
     // When
     char address_str[70];
-    tcs_address_to_str(&addr, address_str);
+    tcs_address_to_str(&addr, address_str, sizeof address_str, NULL);
 
     // Then
     CHECK_EQ(address_str, "127.0.0.1:1234");
@@ -2770,7 +2770,7 @@ TEST_CASE("IPv6 address to string loopback")
     addr.family = TCS_FAMILY_IPV6;
     addr.data.ipv6.address = TCS_ADDRESS_IPV6_LOOPBACK;
     char str[70];
-    CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+    CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
     CHECK_EQ(str, "::1");
 }
 
@@ -2780,7 +2780,7 @@ TEST_CASE("IPv6 address to string all-zeros")
     addr.family = TCS_FAMILY_IPV6;
     addr.data.ipv6.address = TCS_ADDRESS_IPV6_ANY;
     char str[70];
-    CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+    CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
     CHECK_EQ(str, "::");
 }
 
@@ -2791,7 +2791,7 @@ TEST_CASE("IPv6 address to string with port")
     addr.data.ipv6.address = TCS_ADDRESS_IPV6_LOOPBACK;
     addr.data.ipv6.port = 8080;
     char str[70];
-    CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+    CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
     CHECK_EQ(str, "[::1]:8080");
 }
 
@@ -2802,27 +2802,27 @@ TEST_CASE("IPv6 address to string RFC 5952 compliance")
 
     // Leading zeros suppressed
     CHECK(tcs_address_parse("2001:0db8::0001", &addr) == TCS_SUCCESS);
-    CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+    CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
     CHECK_EQ(str, "2001:db8::1");
 
     // Single zero group NOT compressed to ::
     CHECK(tcs_address_parse("2001:db8:0:1:1:1:1:1", &addr) == TCS_SUCCESS);
-    CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+    CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
     CHECK_EQ(str, "2001:db8:0:1:1:1:1:1");
 
     // Longest zero run compressed, first run wins on tie
     CHECK(tcs_address_parse("1:0:0:2:0:0:0:3", &addr) == TCS_SUCCESS);
-    CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+    CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
     CHECK_EQ(str, "1:0:0:2::3");
 
     // Equal length runs: first wins
     CHECK(tcs_address_parse("1:0:0:2:3:0:0:4", &addr) == TCS_SUCCESS);
-    CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+    CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
     CHECK_EQ(str, "1::2:3:0:0:4");
 
     // Lowercase hex
     CHECK(tcs_address_parse("ABCD:EF01::1", &addr) == TCS_SUCCESS);
-    CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+    CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
     CHECK_EQ(str, "abcd:ef01::1");
 }
 
@@ -2834,7 +2834,7 @@ TEST_CASE("IPv6 address roundtrip")
         TcsAddress addr;
         CHECK(tcs_address_parse(inputs[i], &addr) == TCS_SUCCESS);
         char str[70];
-        CHECK(tcs_address_to_str(&addr, str) == TCS_SUCCESS);
+        CHECK(tcs_address_to_str(&addr, str, sizeof str, NULL) == TCS_SUCCESS);
         CHECK_EQ(str, inputs[i]);
     }
 }