Hi folks!
Firefox already lets users indirectly improve readability of overly wide webpages by opening the sidebar or docking DevTools to the side, then resizing that panel. This narrows the webpage viewport and often makes long-form pages, documentation, forums, and text-heavy sites much easier to read.
However, the sidebar or DevTools content itself is usually irrelevant and visually distracting. It would be useful to have a simple toggle that hides the contents of the side panel while keeping its width, effectively turning it into a blank “curtain” or spacer.
Suggested behavior:
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In the sidebar and side-docked DevTools, add a small toggle such as “Hide panel contents,” “Curtain mode,” or “Spacer mode.”
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When enabled, the panel keeps its current width but displays only a neutral blank surface.
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The webpage viewport remains narrowed exactly as if the panel were open.
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The user can drag the curtain width as usual.
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Clicking the toggle again restores the normal sidebar or DevTools contents.
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Optional: allow left, right, or both-side curtains for centered reading width.
Why this helps:
Many modern webpages use very wide layouts that are uncomfortable for reading. Reader View is excellent when available, but it does not work on all pages, documentation sites, forums, web apps, or pages where the user wants to keep the original layout. A curtain/spacer mode would give users a quick, built-in way to reduce readable line length without zooming, editing CSS, installing extensions, or keeping distracting DevTools/sidebar content visible.
This would be useful for reading documentation, articles, forums, issue trackers, long comments, and pages where Responsive Design Mode or Reader View is not ideal.
The feature could be considered an accessibility/readability improvement: it gives users control over line length and page width while preserving the actual site layout.
