Reading Helper Ruler has been rebuilt from the ground up. It now works on Chrome, Edge, and Firefox from the same release, with a redesigned popup and several new ways to customize your reading line.

New:

Quick-adjust panel: hold Shift to resize the bar, lock it in place, or reset it directly on the page — no need to open the popup.
Full window width mode with proper handling when you resize your browser.
Position indicator: shows exactly where your cursor is along a locked or full-width bar, with a choice of shape (triangle, line, diamond).
Highlighter blend style plus a new fluorescent color palette alongside the original colors.
Save, apply, and delete configuration profiles, so you can build a look once and reuse it on any site.
Redesigned, more compact popup with live value tooltips on every slider.
Fixed:

The keyboard shortcut shown in the popup now always matches what's actually bound on your system.
Settings changes no longer risk hitting the browser's storage write limits during rapid adjustments.
Several smaller bugs from the previous version.
Under the hood:

Migrated to Manifest V3 for long-term compatibility with Chrome and Firefox.

Added a feature to use the full window width activated / deactivated via checkbox in the properties panel.

Core Functionality

Dynamic rectangle overlay that tracks mouse movement across web pages.
Configurable dimensions (width and height).
Customizable colors with an integrated visual picker.
Adjustable opacity control.
Vertical offset adjustment relative to mouse position.

Advanced Movement Controls
Smooth downward movement via Shift + Ctrl keyboard shortcut. Continuous animation when keys are held.
Automatic boundary detection to keep the rectangle within the viewport.
Resize the ruler using Ctrl + Alt + Arrow keys.

User Interface Features

Popup interface with intuitive controls, including:
Toggle button for activation and deactivation.
Interactive sliders for all adjustable parameters.
Real-time color selection with visual feedback.
Linked height/offset mode for synchronized adjustments.
Status panel displaying the current domain and activation state.

Persistence & Customization

Domain-specific configurations, allowing different settings per website.
Automatic saving via browser sync storage.
Persistent active/inactive state across browsing sessions.
Quick toggle using a dedicated keyboard shortcut (Ctrl + Shift + L).

General Bug fixes.