Reading Ruler is a free Google Chrome extension developed by Denison Linus. This useful tool is designed to assist readers while reading long texts on web pages. It is particularly useful for dyslexic readers who often struggle to keep their place on the page while reading.

The extension comes with several useful features to improve the reading experience. These include highlighting the current reading line, moving the current line with arrow keys, automatic jump to next/previous page, smart adjustment when page resizes, color, opacity and shadow adjustments.

Using Reading Ruler is simple. Double click on the text to start and use the up and down arrow keys to navigate. If you want to cancel, simply press the ESC key.

One of the best things about Reading Ruler is that it doesn't collect any user data or track users. The extension also doesn't use any kind of server connection, which means all the processing is done locally. The extension requires the "read and change websites" permission to access website elements to calculate and render the ruler.

For those interested, the source code for the extension is available on GitHub.