diff --git a/README.md b/README.md
index a542b2ad..ec4b5959 100644
--- a/README.md
+++ b/README.md
@@ -45,6 +45,12 @@ The variant is updated:
 
 However, be advised that the plugin using nvim-web-devicons may have cached the icons.
 
+### Case Sensitivity
+
+Filename icons e.g. `"Dockerfile"` are case insensitively matched.
+
+Extension icons e.g. `"lua"` are case sensitive.
+
 ### Setup
 
 This adds all the highlight groups for the devicons
diff --git a/lua/nvim-web-devicons.lua b/lua/nvim-web-devicons.lua
index 44cbc7ec..1931d330 100644
--- a/lua/nvim-web-devicons.lua
+++ b/lua/nvim-web-devicons.lua
@@ -353,6 +353,24 @@ local function get_highlight_ctermfg(icon_data)
   return nvim_get_hl_by_name(get_highlight_name(icon_data), false).foreground
 end
 
+---Change all keys in a table to lowercase
+---@param t table
+local function lowercase_keys(t)
+  if not t then
+    return
+  end
+
+  for k, v in pairs(t) do
+    if type(k) == "string" then
+      local lower_k = k:lower()
+      if lower_k ~= k then
+        t[lower_k] = v
+        t[k] = nil
+      end
+    end
+  end
+end
+
 local loaded = false
 
 function M.has_loaded()
@@ -396,6 +414,11 @@ function M.setup(opts)
   local user_desktop_environment_icons = user_icons.override_by_desktop_environment
   local user_window_manager_icons = user_icons.override_by_window_manager
 
+  -- filename matches are case insensitive
+  lowercase_keys(icons_by_filename)
+  lowercase_keys(user_icons.override)
+  lowercase_keys(user_icons.override_by_filename)
+
   icons = vim.tbl_extend(
     "force",
     icons,