diff --git a/README.md b/README.md
index 3e04acb..b4f3fa8 100644
--- a/README.md
+++ b/README.md
@@ -23,10 +23,10 @@
 
 ## ✅ TODO
 
-- [ ] health checks: check merge conflicts async
-  - [ ] unsupported props or props from other managers
-  - [ ] other packages still in site?
-  - [ ] other package manager artifacts still present? compiled etc
+- [x] health checks: check merge conflicts async
+  - [x] unsupported props or props from other managers
+  - [x] other packages still in site?
+  - [x] other package manager artifacts still present? compiled etc
 - [ ] fix plugin details
 - [ ] show disabled plugins (strikethrough?)
 - [ ] log file
diff --git a/lua/lazy/health.lua b/lua/lazy/health.lua
new file mode 100644
index 0000000..612736d
--- /dev/null
+++ b/lua/lazy/health.lua
@@ -0,0 +1,57 @@
+local Util = require("lazy.util")
+local Config = require("lazy.core.config")
+
+local M = {}
+
+function M.check()
+  vim.health.report_start("lazy.nvim")
+
+  local existing = false
+  Util.ls(vim.fn.stdpath("data") .. "/site/pack/", function(path)
+    existing = true
+    vim.health.report_warn("found existing packages at `" .. path .. "`")
+  end)
+  if not existing then
+    vim.health.report_ok("no existing packages found by other package managers")
+  end
+
+  local packer_compiled = vim.fn.stdpath("config") .. "/plugin/packer_compiled.lua"
+  if vim.loop.fs_stat(packer_compiled) then
+    vim.health.report_error("please remove the file `" .. packer_compiled .. "`")
+  else
+    vim.health.report_ok("packer_compiled.lua not found")
+  end
+
+  local valid = {
+    1,
+    "name",
+    "uri",
+    "enabled",
+    "lazy",
+    "dev",
+    "dependencies",
+    "init",
+    "config",
+    "build",
+    "branch",
+    "tag",
+    "commit",
+    "version",
+    "pin",
+    "cmd",
+    "event",
+    "keys",
+    "ft",
+    "dir",
+    "_",
+  }
+  for _, plugin in pairs(Config.plugins) do
+    for key in pairs(plugin) do
+      if not vim.tbl_contains(valid, key) then
+        vim.health.report_warn("{" .. plugin.name .. "}: unknown key <" .. key .. ">")
+      end
+    end
+  end
+end
+
+return M