Edge is an on-screen ruler that supports multiple units, horizontal & vertical orientation, and looks like a native application.

This is a typical developer tool, but muggles like me can use this once in a while for measuring things online.

Note: I couldn’t get this working on my Chromebook. I am guessing this is a non-Chrome OS app.

Here is the official list of features:

* Support for pixels, inches, and centimeters
* Both Horizontal and Vertical rulers
* Move the ruler with your arrow keys (+ shift for 10px changes)
* resize the ruler with your arrow keys + alt (+ shift for 100px changes)
* Calibrate the ruler with your screen size
* Exists separately from any browser tab
* Easily resizable
* Settings are remembered across launches
* Always on top mode

You can download Edge from here.