diff --git a/readme.md b/readme.md
index 88e1a50..135a528 100644
--- a/readme.md
+++ b/readme.md
@@ -163,3 +163,4 @@ Inspired by [awesome](https://github.com/sindresorhus/awesome).
 
 PRs welcome!
 
+- [KeyboardTester.click Online Ruler](https://keyboardtester.click/online-ruler.php) - Free browser SVG ruler in actual size (cm + inches), calibrate with credit card or DPI. Useful for verifying physical dimensions on screen.