diff --git a/builtin/game/register.lua b/builtin/game/register.lua
index 3e4b9be968ac7..b41fd0c3e55af 100644
--- a/builtin/game/register.lua
+++ b/builtin/game/register.lua
@@ -91,7 +91,14 @@ local function check_node_list(list, field)
 end
 
 function core.register_abm(spec)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_abm cannot be called after mods are loaded.")
+		return
+	end
 	-- Add to core.registered_abms
+	if spec.name then
+		check_modname_prefix(spec.name)
+	end
 	check_node_list(spec.nodenames, "nodenames")
 	check_node_list(spec.neighbors, "neighbors")
 	assert(type(spec.action) == "function", "Required field 'action' of type function")
@@ -99,7 +106,31 @@ function core.register_abm(spec)
 	spec.mod_origin = core.get_current_modname() or "??"
 end
 
+function core.override_abm(name, redefinition)
+	if core.is_mods_loaded then
+		core.log("error", "Function override_abm cannot be called after mods are loaded.")
+		return
+	end
+	-- Override abm in core.registered_abms
+	if redefinition.name ~= nil then
+		error("Attempt to redefine abm name of "..name.." to "..dump(redefinition.name), 2)
+	end
+	check_node_list(redefinition.nodenames, "nodenames")
+	for _, abm in pairs(core.registered_abms) do
+		if (abm.name == name) then
+			for k, v in pairs(redefinition) do
+				rawset(abm, k, v)
+			end
+			return
+		end
+	end
+end
+
 function core.register_lbm(spec)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_lbm cannot be called after mods are loaded.")
+		return
+	end
 	-- Add to core.registered_lbms
 	check_modname_prefix(spec.name)
 	check_node_list(spec.nodenames, "nodenames")
@@ -113,7 +144,32 @@ function core.register_lbm(spec)
 	spec.mod_origin = core.get_current_modname() or "??"
 end
 
+function core.override_lbm(name, redefinition)
+	if core.is_mods_loaded then
+		core.log("error", "Function override_lbm cannot be called after mods are loaded.")
+		return
+	end
+	-- Override lbm in core.registered_lbms
+	if redefinition.name ~= nil then
+		error("Attempt to redefine lbm name of "..name.." to "..dump(redefinition.name), 2)
+	end
+	check_node_list(redefinition.nodenames, "nodenames")
+	assert(type(redefinition.action) == "function", "Required field 'action' of type function")
+	for _, lbm in pairs(core.registered_lbms) do
+		if (lbm.name == name) then
+			for k, v in pairs(redefinition) do
+				rawset(lbm, k, v)
+			end
+			return
+		end
+	end
+end
+
 function core.register_entity(name, prototype)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_entity cannot be called after mods are loaded.")
+		return
+	end
 	-- Check name
 	if name == nil then
 		error("Unable to register entity: Name is nil")
@@ -128,7 +184,35 @@ function core.register_entity(name, prototype)
 	prototype.mod_origin = core.get_current_modname() or "??"
 end
 
+function core.override_entity(name, redefinition)
+	if core.is_mods_loaded then
+		core.log("error", "Function override_entity cannot be called after mods are loaded.")
+		return
+	end
+	if redefinition.name ~= nil then
+		error("Attempt to redefine entity name of "..name.." to "..dump(redefinition.name), 2)
+	end
+	local entity = core.registered_entities[name]
+	if not entity then
+		error("Attempt to override non-existent entity "..name, 2)
+	end
+	for k, v in pairs(redefinition) do
+		if k ~= "initial_properties" then
+			rawset(entity, k, v)
+		else
+			for k2, v2 in pairs(v) do
+				rawset(entity.initial_properties, k2, v2)
+			end
+		end
+	end
+	core.registered_entities[name] = entity
+end
+
 function core.register_item(name, itemdef)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_item cannot be called after mods are loaded.")
+		return
+	end
 	-- Check name
 	if name == nil then
 		error("Unable to register item: Name is nil")
@@ -204,6 +288,10 @@ function core.register_item(name, itemdef)
 end
 
 function core.unregister_item(name)
+	if core.is_mods_loaded then
+		core.log("error", "Function unregister_item cannot be called after mods are loaded.")
+		return
+	end
 	if not core.registered_items[name] then
 		core.log("warning", "Not unregistering item " ..name..
 			" because it doesn't exist.")
@@ -225,11 +313,19 @@ function core.unregister_item(name)
 end
 
 function core.register_node(name, nodedef)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_node cannot be called after mods are loaded.")
+		return
+	end
 	nodedef.type = "node"
 	core.register_item(name, nodedef)
 end
 
 function core.register_craftitem(name, craftitemdef)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_craftitem cannot be called after mods are loaded.")
+		return
+	end
 	craftitemdef.type = "craft"
 
 	-- BEGIN Legacy stuff
@@ -242,6 +338,10 @@ function core.register_craftitem(name, craftitemdef)
 end
 
 function core.register_tool(name, tooldef)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_tool cannot be called after mods are loaded.")
+		return
+	end
 	tooldef.type = "tool"
 	tooldef.stack_max = 1
 
@@ -293,6 +393,10 @@ function core.register_tool(name, tooldef)
 end
 
 function core.register_alias(name, convert_to)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_alias cannot be called after mods are loaded.")
+		return
+	end
 	if forbidden_item_names[name] then
 		error("Unable to register alias: Name is forbidden: " .. name)
 	end
@@ -307,6 +411,10 @@ function core.register_alias(name, convert_to)
 end
 
 function core.register_alias_force(name, convert_to)
+	if core.is_mods_loaded then
+		core.log("error", "Function register_alias_force cannot be called after mods are loaded.")
+		return
+	end
 	if forbidden_item_names[name] then
 		error("Unable to register alias: Name is forbidden: " .. name)
 	end
diff --git a/doc/lua_api.md b/doc/lua_api.md
index 6db358c85c5e5..19d1b9c32e038 100644
--- a/doc/lua_api.md
+++ b/doc/lua_api.md
@@ -5851,8 +5851,11 @@ Call these functions only at load time!
       `name` from `core.registered_items` and from the associated item table
       according to its nature: `core.registered_nodes`, etc.
 * `core.register_entity(name, entity definition)`
+* `core.override_entity(name, entity definition)`
 * `core.register_abm(abm definition)`
+* `core.override_abm(name, abm definition)`
 * `core.register_lbm(lbm definition)`
+* `core.override_lbm(name, lbm definition)`
 * `core.register_alias(alias, original_name)`
     * Also use this to set the 'mapgen aliases' needed in a game for the core
       mapgens. See [Mapgen aliases] section above.
@@ -9276,7 +9279,7 @@ Player properties need to be saved manually.
 Entity definition
 -----------------
 
-Used by `core.register_entity`.
+Used by `core.register_entity` and `core.override_entity`.
 The entity definition table becomes a metatable of a newly created per-entity
 luaentity table, meaning its fields (e.g. `initial_properties`) will be shared
 between all instances of an entity.
@@ -9314,7 +9317,7 @@ between all instances of an entity.
 ABM (ActiveBlockModifier) definition
 ------------------------------------
 
-Used by `core.register_abm`.
+Used by `core.register_abm` and `core.override_abm`.
 
 ```lua
 {
@@ -9322,6 +9325,10 @@ Used by `core.register_abm`.
     -- Descriptive label for profiling purposes (optional).
     -- Definitions with identical labels will be listed as one.
 
+    name = "modname:replace_legacy_door",
+    -- Optional filed, required for make ABM overridable.
+    -- Identifier of the ABM, should follow the modname:<whatever> convention.
+
     nodenames = {"default:lava_source"},
     -- Apply `action` function to these nodes.
     -- `group:groupname` can also be used here.
@@ -9368,7 +9375,7 @@ Used by `core.register_abm`.
 LBM (LoadingBlockModifier) definition
 -------------------------------------
 
-Used by `core.register_lbm`.
+Used by `core.register_lbm` and `core.override_lbm`.
 
 A loading block modifier (LBM) is used to define a function that is called for
 specific nodes (defined by `nodenames`) when a mapblock which contains such nodes
@@ -9386,7 +9393,8 @@ contain a matching node.
     -- Definitions with identical labels will be listed as one.
 
     name = "modname:replace_legacy_door",
-    -- Identifier of the LBM, should follow the modname:<whatever> convention
+    -- Identifier of the LBM, should follow the modname:<whatever> convention.
+    -- Also used for overriding LBM.
 
     nodenames = {"default:lava_source"},
     -- List of node names to trigger the LBM on.
diff --git a/games/devtest/mods/testabms/after_node.lua b/games/devtest/mods/testabms/after_node.lua
index fa2b3ab1600ca..d0d9d8866a345 100644
--- a/games/devtest/mods/testabms/after_node.lua
+++ b/games/devtest/mods/testabms/after_node.lua
@@ -9,4 +9,3 @@ core.register_node("testabms:after_abm", {
 
 	groups = { dig_immediate = 3 },
 })
-
diff --git a/games/devtest/mods/testabms/chances.lua b/games/devtest/mods/testabms/chances.lua
index a84e75260fcae..06f22605aca9b 100644
--- a/games/devtest/mods/testabms/chances.lua
+++ b/games/devtest/mods/testabms/chances.lua
@@ -53,4 +53,3 @@ core.register_abm({
 		meta:set_string("infotext", "ABM testabsm:chance_20 changed this node.")
 	end
 })
-
diff --git a/games/devtest/mods/testabms/init.lua b/games/devtest/mods/testabms/init.lua
index 8bf4975cf9738..0926f6498cda0 100644
--- a/games/devtest/mods/testabms/init.lua
+++ b/games/devtest/mods/testabms/init.lua
@@ -5,3 +5,4 @@ dofile(path.."/chances.lua")
 dofile(path.."/intervals.lua")
 dofile(path.."/min_max.lua")
 dofile(path.."/neighbors.lua")
+dofile(path.."/override.lua")
diff --git a/games/devtest/mods/testabms/intervals.lua b/games/devtest/mods/testabms/intervals.lua
index 928406508b160..8f432f21d3352 100644
--- a/games/devtest/mods/testabms/intervals.lua
+++ b/games/devtest/mods/testabms/intervals.lua
@@ -53,4 +53,3 @@ core.register_abm({
 		meta:set_string("infotext", "ABM testabsm:interval_60 changed this node.")
 	end
 })
-
diff --git a/games/devtest/mods/testabms/min_max.lua b/games/devtest/mods/testabms/min_max.lua
index b5df4e40ec00d..7b26b08d9d48e 100644
--- a/games/devtest/mods/testabms/min_max.lua
+++ b/games/devtest/mods/testabms/min_max.lua
@@ -55,4 +55,3 @@ core.register_abm({
 		meta:set_string("infotext", "ABM testabsm:max_y changed this node.")
 	end
 })
-
diff --git a/games/devtest/mods/testabms/neighbors.lua b/games/devtest/mods/testabms/neighbors.lua
index 0ce21c23cec2f..ca79edfc2b52b 100644
--- a/games/devtest/mods/testabms/neighbors.lua
+++ b/games/devtest/mods/testabms/neighbors.lua
@@ -96,4 +96,3 @@ core.register_abm({
 			"ABM testabsm:required_missing_neighbor changed this node.")
 	end
 })
-
diff --git a/games/devtest/mods/testabms/override.lua b/games/devtest/mods/testabms/override.lua
new file mode 100644
index 0000000000000..6c2fe0918e6af
--- /dev/null
+++ b/games/devtest/mods/testabms/override.lua
@@ -0,0 +1,40 @@
+-- test ABMs with override
+
+local S = core.get_translator("testabms")
+
+-- ABM override
+core.register_node("testabms:override", {
+	description = S("Node for test ABM override"),
+	drawtype = "normal",
+	tiles = { "testabms_wait_node.png" },
+
+	groups = { dig_immediate = 3 },
+	
+	on_construct = function (pos)
+		local meta = core.get_meta(pos)
+		meta:set_string("infotext", "Waiting for ABM testabms:overrid")
+	end,
+})
+
+core.register_abm({
+		label = "testabms:override",
+		name = "testabms:override",
+		nodenames = "testabms:override",
+		interval = 1000,
+		chance = 5000,
+		action = function (pos)
+			core.swap_node(pos, {name="testabms:after_abm"})
+			local meta = core.get_meta(pos)
+			meta:set_string("infotext", "ABM testabms:override changed this node.")
+		end
+	})
+
+core.override_abm("testabms:override", {
+		interval = 1,
+		chance = 1,
+		action = function (pos)
+			core.swap_node(pos, {name="testabms:after_abm"})
+			local meta = core.get_meta(pos)
+			meta:set_string("infotext", "Override ABM testabms:override changed this node.")
+		end
+	})
diff --git a/games/devtest/mods/testlbms/README.md b/games/devtest/mods/testlbms/README.md
new file mode 100644
index 0000000000000..0be7847bb882e
--- /dev/null
+++ b/games/devtest/mods/testlbms/README.md
@@ -0,0 +1,5 @@
+# Test LBMs
+
+This mod contains a nodes and related LBM actions.
+By placing these nodes, you can test basic LBM behaviours.
+
diff --git a/games/devtest/mods/testlbms/init.lua b/games/devtest/mods/testlbms/init.lua
new file mode 100644
index 0000000000000..06d11d7fd2ee2
--- /dev/null
+++ b/games/devtest/mods/testlbms/init.lua
@@ -0,0 +1,45 @@
+local S = minetest.get_translator("testlbms")
+
+-- After LBM node
+minetest.register_node("testlbms:after_lbm", {
+	description = S("After LBM processed node."),
+	drawtype = "normal",
+	tiles = { "testlbms_after_node.png" },
+
+	groups = { dig_immediate = 3 },
+})
+
+-- LBM onload change
+minetest.register_node("testlbms:onload_change", {
+	description = S("Node for test LBM"),
+	drawtype = "normal",
+	tiles = { "testlbms_wait_node.png" },
+
+	groups = { dig_immediate = 3 },
+	
+	on_construct = function (pos)
+		local meta = minetest.get_meta(pos)
+		meta:set_string("infotext", "Waiting for LBM testlbms:chance_5")
+	end,
+})
+
+minetest.register_lbm({
+		label = "testlbms:onload_change",
+		name = "testlbms:onload_change",
+		nodenames = "testlbms:onload_change",
+		run_at_every_load = true,
+		action = function (pos)
+			minetest.swap_node(pos, {name="testlbms:after_lbm"})
+			local meta = minetest.get_meta(pos)
+			meta:set_string("infotext", "LBM testlbms:onload_change changed this node.")
+		end
+	})
+
+minetest.override_lbm("testlbms:onload_change", {
+		action = function (pos)
+			minetest.swap_node(pos, {name="testlbms:after_lbm"})
+			local meta = minetest.get_meta(pos)
+			meta:set_string("infotext", "Override LBM testlbms:onload_change changed this node.")
+		end,
+	})
+
diff --git a/games/devtest/mods/testlbms/mod.conf b/games/devtest/mods/testlbms/mod.conf
new file mode 100644
index 0000000000000..b94f5e1301e63
--- /dev/null
+++ b/games/devtest/mods/testlbms/mod.conf
@@ -0,0 +1,2 @@
+name = testlbms
+description = Contains some nodes for test LBMs.
diff --git a/games/devtest/mods/testlbms/textures/testlbms_after_node.png b/games/devtest/mods/testlbms/textures/testlbms_after_node.png
new file mode 100644
index 0000000000000..9bdb1987d979a
Binary files /dev/null and b/games/devtest/mods/testlbms/textures/testlbms_after_node.png differ
diff --git a/games/devtest/mods/testlbms/textures/testlbms_wait_node.png b/games/devtest/mods/testlbms/textures/testlbms_wait_node.png
new file mode 100644
index 0000000000000..3d26f0c07523b
Binary files /dev/null and b/games/devtest/mods/testlbms/textures/testlbms_wait_node.png differ
diff --git a/games/devtest/mods/unittests/entity.lua b/games/devtest/mods/unittests/entity.lua
index af91a2a943544..0848225d46864 100644
--- a/games/devtest/mods/unittests/entity.lua
+++ b/games/devtest/mods/unittests/entity.lua
@@ -13,7 +13,7 @@ end
 
 core.register_entity("unittests:callbacks", {
 	initial_properties = {
-		hp_max = 5,
+		hp_max = 1,
 		visual = "upright_sprite",
 		textures = { "unittests_callback.png" },
 		static_save = false,
@@ -76,6 +76,13 @@ core.register_entity("unittests:callbacks", {
 	end,
 })
 
+core.override_entity("unittests:callbacks", {
+		initial_properties = {
+			hp_max = 5,
+		},
+		_lua_hp_max = 6,
+	})
+
 --
 
 local function check_log(expect)
@@ -234,3 +241,21 @@ local function test_get_bone_rot(_, pos)
 	end
 end
 unittests.register("test_get_bone_rot", test_get_bone_rot, {map=true})
+
+unittests.register("test_entity_override", function(_, pos)
+	log = {}
+
+	local obj = core.add_entity(pos, "unittests:callbacks")
+	check_log({"on_activate(0)"})
+
+	-- check properties
+	local props = obj:get_properties()
+	assert(props.hp_max == 5)
+	assert(props.visual == "upright_sprite")
+
+	-- check entity
+	local lua = obj:get_luaentity()
+	assert(lua._lua_hp_max == 6)
+
+	obj:remove()
+end, {map=true})
diff --git a/src/script/cpp_api/s_client.cpp b/src/script/cpp_api/s_client.cpp
index 772bc24121af1..2c3c7e58cdaa9 100644
--- a/src/script/cpp_api/s_client.cpp
+++ b/src/script/cpp_api/s_client.cpp
@@ -25,6 +25,10 @@ void ScriptApiClient::on_mods_loaded()
 	} catch (LuaError &e) {
 		getClient()->setFatalError(e);
 	}
+	// set is_mods_loaded
+	lua_getglobal(L, "core");
+	lua_pushboolean(L, true);
+	lua_setfield(L, -2, "is_mods_loaded");
 }
 
 void ScriptApiClient::on_shutdown()
diff --git a/src/script/cpp_api/s_server.cpp b/src/script/cpp_api/s_server.cpp
index faacf97141f7a..933ded7367496 100644
--- a/src/script/cpp_api/s_server.cpp
+++ b/src/script/cpp_api/s_server.cpp
@@ -147,6 +147,10 @@ void ScriptApiServer::on_mods_loaded()
 	lua_getfield(L, -1, "registered_on_mods_loaded");
 	// Call callbacks
 	runCallbacks(0, RUN_CALLBACKS_MODE_FIRST);
+	// set is_mods_loaded
+	lua_getglobal(L, "core");
+	lua_pushboolean(L, true);
+	lua_setfield(L, -2, "is_mods_loaded");
 }
 
 void ScriptApiServer::on_shutdown()
diff --git a/src/unittest/test_servermodmanager.cpp b/src/unittest/test_servermodmanager.cpp
index 500d0f2884950..65a33f027b84f 100644
--- a/src/unittest/test_servermodmanager.cpp
+++ b/src/unittest/test_servermodmanager.cpp
@@ -107,7 +107,7 @@ void TestServerModManager::testGetMods()
 	ServerModManager sm(m_worlddir);
 	const auto &mods = sm.getMods();
 	// `ls ./games/devtest/mods | wc -l` + 1 (test mod)
-	UASSERTEQ(std::size_t, mods.size(), 34 + 1);
+	UASSERTEQ(std::size_t, mods.size(), 35 + 1);
 
 	// Ensure we found basenodes mod (part of devtest)
 	// and test_mod (for testing MINETEST_MOD_PATH).