diff --git a/.test/tests.lua b/.test/tests.lua
index 6b96236..43407fb 100644
--- a/.test/tests.lua
+++ b/.test/tests.lua
@@ -5,6 +5,7 @@ package.path = package.path .. ";../?.lua"
 
 local assert = require("batteries.assert")
 local tablex = require("batteries.tablex")
+local identifier = require("batteries.identifier")
 
 -- tablex {{{
 
@@ -155,3 +156,43 @@ local function test_spairs()
 		10, 8, 7
 	}))
 end
+
+local function test_uuid4()
+	for i = 1, 5 do
+		local id = identifier.uuid4()
+
+		-- right len
+		assert(#id == 36)
+		-- right amount of non hyphen characters
+		assert(#id:gsub("-", "") == 32)
+
+		-- 15th char is always a 4
+		assert(id:sub(15, 15) == "4")
+		-- 20th char is always between 0x8 and 0xb
+		local y = tonumber("0x" .. id:sub(20, 20))
+		assert(y >= 0x8 and y <= 0xb)
+
+		-- everything is a valid 8 bit num
+		for char in id:gsub("-", ""):gmatch(".") do
+			local num = assert(tonumber("0x" .. char))
+			assert(num >= 0 and num <= 0xf)
+		end
+	end
+end
+
+local function test_ulid()
+	-- bail if there's no appropriate time func
+	if select(2, pcall(identifier.ulid)):find('time function') then return end
+
+	for i = 1, 5 do
+		local ulid = assert(identifier.ulid())
+
+		-- right len
+		assert(#ulid == 26)
+		-- have the same timestamp with the same time
+		local a, b = identifier.ulid(nil, 1):sub(1, 10), identifier.ulid(nil, 1):sub(1, 10)
+		assert(a == b)
+		-- don't have characters out of crockford base32
+		assert(not ulid:match("[ILOU%l]"))
+	end
+end
diff --git a/identifier.lua b/identifier.lua
new file mode 100644
index 0000000..e7352e4
--- /dev/null
+++ b/identifier.lua
@@ -0,0 +1,76 @@
+--[[
+	identifier generation
+
+	uuid is version 4, ulid is an alternative to uuid (see
+	https://github.com/ulid/spec).
+
+	todo:
+		this ulid isn't guaranteed to be sortable for ulids generated
+		within the same second yet
+]]
+
+local path = (...):gsub("identifier", "")
+
+local identifier = {}
+
+--(internal; use a provided random generator object, or not)
+local function _random(rng, ...)
+	if rng then return rng:random(...) end
+	if love then return love.math.random(...) end
+	return math.random(...)
+end
+
+local uuid4_template = "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx"
+
+--generate a UUID version 4
+function identifier.uuid4(rng)
+	--x should be 0x0-0xf, the single y should be 0x8-0xb
+	--4 should always just be 4 (denoting uuid version)
+    local out = uuid4_template:gsub("[xy]", function (c)
+        return string.format(
+			"%x",
+			c == "x" and _random(rng, 0x0, 0xf) or _random(rng, 0x8, 0xb)
+		)
+    end)
+
+	return out
+end
+
+--crockford's base32 https://en.wikipedia.org/wiki/Base32
+local _encoding = {
+	"0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
+	"A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "M",
+	"N", "P", "Q", "R", "S", "T", "V", "W", "X", "Y", "Z"
+}
+
+--since ulid needs time since unix epoch with miliseconds, we can just
+--use socket. if that's not loaded, they'll have to provide their own
+local function _now(time_func, ...)
+	if package.loaded.socket then return package.loaded.socket.gettime(...) end
+	if pcall(require, "socket") then return require("socket").gettime(...) end
+	if time_func then return time_func(...) end
+	error("assertion failed: socket can't be found and no time function provided")
+end
+
+--generate an ULID using this rng at this time (now by default)
+--implementation based on https://github.com/Tieske/ulid.lua
+function identifier.ulid(rng, time)
+	time = math.floor((time or _now()) * 1000)
+
+	local time_part = {}
+	local random_part = {}
+
+	for i = 10, 1, -1 do
+		local mod = time % #_encoding
+		time_part[i] = _encoding[mod + 1]
+		time = (time - mod) / #_encoding
+	end
+
+	for i = 1, 16 do
+		random_part[i] = _encoding[math.floor(_random(rng) * #_encoding) + 1]
+	end
+
+	return table.concat(time_part) .. table.concat(random_part)
+end
+
+return identifier