diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index 3e2742de110..46e509cb8f0 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -125,6 +125,9 @@ var/path_type = /obj/item/baseball_bat
 var/path_type = "/obj/item/baseball_bat"
 ```
 
+### Use var/name format when declaring variables
+While DM allows other ways of declaring variables, this one should be used for consistency.
+
 ### Tabs, not spaces
 You must use tabs to indent your code, NOT SPACES.
 
diff --git a/code/_onclick/hud/action_button.dm b/code/_onclick/hud/action_button.dm
index 85ecd036de6..d4d2c2d8a53 100644
--- a/code/_onclick/hud/action_button.dm
+++ b/code/_onclick/hud/action_button.dm
@@ -78,7 +78,7 @@
 
 
 /obj/screen/movable/action_button/hide_toggle/proc/InitialiseIcon(datum/hud/owner_hud)
-	var settings = owner_hud.get_action_buttons_icons()
+	var/settings = owner_hud.get_action_buttons_icons()
 	icon = settings["bg_icon"]
 	icon_state = settings["bg_state"]
 	hide_icon = settings["toggle_icon"]
diff --git a/code/datums/ai_laws.dm b/code/datums/ai_laws.dm
index 24daad00f9e..2222a959bcc 100644
--- a/code/datums/ai_laws.dm
+++ b/code/datums/ai_laws.dm
@@ -310,7 +310,7 @@
 		replaceable_groups[LAW_INHERENT] = inherent.len
 	if(supplied.len && (LAW_SUPPLIED in groups))
 		replaceable_groups[LAW_SUPPLIED] = supplied.len
-	var picked_group = pickweight(replaceable_groups)
+	var/picked_group = pickweight(replaceable_groups)
 	switch(picked_group)
 		if(LAW_ZEROTH)
 			. = zeroth
diff --git a/code/game/gamemodes/antag_spawner.dm b/code/game/gamemodes/antag_spawner.dm
index 9b585ea6532..64b405bbd59 100644
--- a/code/game/gamemodes/antag_spawner.dm
+++ b/code/game/gamemodes/antag_spawner.dm
@@ -261,7 +261,7 @@
 
 /obj/item/antag_spawner/slaughter_demon/spawn_antag(client/C, turf/T, type = "")
 
-	var /obj/effect/dummy/slaughter/holder = new /obj/effect/dummy/slaughter(T)
+	var/obj/effect/dummy/slaughter/holder = new /obj/effect/dummy/slaughter(T)
 	var/mob/living/simple_animal/slaughter/S = new demon_type(holder)
 	S.holder = holder
 	S.key = C.key
diff --git a/code/game/gamemodes/miniantags/slaughter/slaughterevent.dm b/code/game/gamemodes/miniantags/slaughter/slaughterevent.dm
index bcb2218fe69..888a10669e7 100644
--- a/code/game/gamemodes/miniantags/slaughter/slaughterevent.dm
+++ b/code/game/gamemodes/miniantags/slaughter/slaughterevent.dm
@@ -33,7 +33,7 @@
 		message_admins("No valid spawn locations found, aborting...")
 		return MAP_ERROR
 
-	var /obj/effect/dummy/slaughter/holder = new /obj/effect/dummy/slaughter((pick(spawn_locs)))
+	var/obj/effect/dummy/slaughter/holder = new /obj/effect/dummy/slaughter((pick(spawn_locs)))
 	var/mob/living/simple_animal/slaughter/S = new /mob/living/simple_animal/slaughter/(holder)
 	S.holder = holder
 	player_mind.transfer_to(S)
diff --git a/code/game/objects/items/RCD.dm b/code/game/objects/items/RCD.dm
index 26cf258c8e8..6e094a5bbb9 100644
--- a/code/game/objects/items/RCD.dm
+++ b/code/game/objects/items/RCD.dm
@@ -144,7 +144,7 @@ obj/item/construction
 	set category = "Object"
 	set src in usr // What does this do?
 
-	var window_type_name
+	var/window_type_name
 
 	if (window_type == /obj/structure/window/fulltile)
 		window_type = /obj/structure/window/reinforced/fulltile
@@ -240,11 +240,11 @@ obj/item/construction
 	set category = "Object"
 	set src in usr
 
-	var airlockcat = input(usr, "Select whether the airlock is solid or glass.") in list("Solid", "Glass")
+	var/airlockcat = input(usr, "Select whether the airlock is solid or glass.") in list("Solid", "Glass")
 	switch(airlockcat)
 		if("Solid")
 			if(advanced_airlock_setting == 1)
-				var airlockpaint = input(usr, "Select the paintjob of the airlock.") in list("Default", "Engineering", "Atmospherics", "Security", "Command", "Medical", "Research", "Mining", "Maintenance", "External", "High Security")
+				var/airlockpaint = input(usr, "Select the paintjob of the airlock.") in list("Default", "Engineering", "Atmospherics", "Security", "Command", "Medical", "Research", "Mining", "Maintenance", "External", "High Security")
 				switch(airlockpaint)
 					if("Default")
 						airlock_type = /obj/machinery/door/airlock
@@ -275,7 +275,7 @@ obj/item/construction
 
 		if("Glass")
 			if(advanced_airlock_setting == 1)
-				var airlockpaint = input(usr, "Select the paintjob of the airlock.") in list("Default", "Engineering", "Atmospherics", "Security", "Command", "Medical", "Research", "Mining")
+				var/airlockpaint = input(usr, "Select the paintjob of the airlock.") in list("Default", "Engineering", "Atmospherics", "Security", "Command", "Medical", "Research", "Mining")
 				switch(airlockpaint)
 					if("Default")
 						airlock_type = /obj/machinery/door/airlock/glass
diff --git a/code/modules/admin/admin.dm b/code/modules/admin/admin.dm
index 48af29616e5..b56caa4e9af 100644
--- a/code/modules/admin/admin.dm
+++ b/code/modules/admin/admin.dm
@@ -431,7 +431,7 @@
 	else
 		rebootconfirm = TRUE
 	if(rebootconfirm)
-		var result = input(usr, "Select reboot method", "World Reboot", options[1]) as null|anything in options
+		var/result = input(usr, "Select reboot method", "World Reboot", options[1]) as null|anything in options
 		if(result)
 			SSblackbox.add_details("admin_verb","Reboot World") //If you are copy-pasting this, ensure the 2nd parameter is unique to the new proc!
 			switch(result)
diff --git a/code/modules/atmospherics/machinery/components/unary_devices/cryo.dm b/code/modules/atmospherics/machinery/components/unary_devices/cryo.dm
index 76455ada491..2e0d1f38054 100644
--- a/code/modules/atmospherics/machinery/components/unary_devices/cryo.dm
+++ b/code/modules/atmospherics/machinery/components/unary_devices/cryo.dm
@@ -349,7 +349,7 @@
 	data["cellTemperature"] = round(air1.temperature, 1)
 
 	data["isBeakerLoaded"] = beaker ? TRUE : FALSE
-	var beakerContents = list()
+	var/beakerContents = list()
 	if(beaker && beaker.reagents && beaker.reagents.reagent_list.len)
 		for(var/datum/reagent/R in beaker.reagents.reagent_list)
 			beakerContents += list(list("name" = R.name, "volume" = R.volume))
diff --git a/code/modules/mining/abandoned_crates.dm b/code/modules/mining/abandoned_crates.dm
index 10512aa5a22..4db42b69333 100644
--- a/code/modules/mining/abandoned_crates.dm
+++ b/code/modules/mining/abandoned_crates.dm
@@ -83,7 +83,7 @@
 			new /obj/item/clothing/suit/hooded/ian_costume(src)
 		if(67 to 68)
 			for(var/i in 1 to rand(4, 7))
-				var /newitem = pick(subtypesof(/obj/item/stock_parts) - /obj/item/stock_parts/subspace)
+				var/newitem = pick(subtypesof(/obj/item/stock_parts) - /obj/item/stock_parts/subspace)
 				new newitem(src)
 		if(69 to 70)
 			for(var/i in 1 to 5)
diff --git a/code/modules/reagents/chemistry/machinery/chem_dispenser.dm b/code/modules/reagents/chemistry/machinery/chem_dispenser.dm
index 538ae996ea7..ec4a1f58f89 100644
--- a/code/modules/reagents/chemistry/machinery/chem_dispenser.dm
+++ b/code/modules/reagents/chemistry/machinery/chem_dispenser.dm
@@ -112,8 +112,8 @@
 	data["maxEnergy"] = cell.maxcharge * powerefficiency
 	data["isBeakerLoaded"] = beaker ? 1 : 0
 
-	var beakerContents[0]
-	var beakerCurrentVolume = 0
+	var/beakerContents[0]
+	var/beakerCurrentVolume = 0
 	if(beaker && beaker.reagents && beaker.reagents.reagent_list.len)
 		for(var/datum/reagent/R in beaker.reagents.reagent_list)
 			beakerContents.Add(list(list("name" = R.name, "volume" = R.volume))) // list in a list because Byond merges the first list...
@@ -129,7 +129,7 @@
 		data["beakerMaxVolume"] = null
 		data["beakerTransferAmounts"] = null
 
-	var chemicals[0]
+	var/chemicals[0]
 	var/is_hallucinating = FALSE
 	if(user.hallucinating())
 		is_hallucinating = TRUE
diff --git a/code/modules/reagents/chemistry/machinery/chem_master.dm b/code/modules/reagents/chemistry/machinery/chem_master.dm
index 802e4c70ca6..c6a01bc45f5 100644
--- a/code/modules/reagents/chemistry/machinery/chem_master.dm
+++ b/code/modules/reagents/chemistry/machinery/chem_master.dm
@@ -133,13 +133,13 @@
 		data["pillBotMaxContent"] = bottle.storage_slots
 
 
-	var beakerContents[0]
+	var/beakerContents[0]
 	if(beaker)
 		for(var/datum/reagent/R in beaker.reagents.reagent_list)
 			beakerContents.Add(list(list("name" = R.name, "id" = R.id, "volume" = R.volume))) // list in a list because Byond merges the first list...
 		data["beakerContents"] = beakerContents
 
-	var bufferContents[0]
+	var/bufferContents[0]
 	if(reagents.total_volume)
 		for(var/datum/reagent/N in reagents.reagent_list)
 			bufferContents.Add(list(list("name" = N.name, "id" = N.id, "volume" = N.volume))) // ^