A simple Firefox extension that lets you set YouTube grid columns (2–8) on Home and main feed pages, hide Shorts shelves, and hide in-feed sponsored/ad tiles. Release notes (0.1.11)

Fixed a bug where the Subscriptions page shelf hiding could miss English Relevance/Latest sections
Restore the documented five-language support for Subscriptions page shelf hiding (Korean, English, Japanese, German, Russian)

Release notes (0.1.10)

Hide the Shorts, Relevance, and Latest shelves on the Subscriptions page
Improve SPA handling for Subscriptions page shelf hiding

Release notes (0.1.9)

Fixed a bug where Home navigation could reset the stored column setting back to the default 4-column layout

Release notes (0.1.8)

Apply the grid layout across YouTube feed-style pages, including Home variants such as /?bp=...
Exclude non-feed pages and the You page (/feed/you) from grid styling

Release notes (0.1.7)

Hide Russian breaking news shelves (for example, "Срочные новости").

Release notes (0.1.6)

Hide German breaking news shelves (for example, "Eilmeldungen").
Hide the top masthead sponsored video section on supported pages.

Release notes (0.1.5)

Show a refresh hint when the popup cannot connect to the YouTube page

Release notes (0.1.4)

Limit the add-on to YouTube Home and main feed pages only (reduced match patterns).
Match the popup UI theme to YouTube dark/light mode.
Hide in-feed sponsored/ad tiles on supported pages.
Polish the popup UI (cleaner button, no reserved status space, clearer slider fill).

Source code: https://github.com/GGyo245/firefox-youtube-grid-columns

GGyo245

Published Firefox add-on:

YouTube Grid Simple