Firefox Browser Add-ons
  • Extensions
  • Themes
    • for Firefox
    • Dictionaries & Language Packs
Log in
Preview of CineCanvas

CineCanvas by Ship of Agony LABs

CineCanvas for YouTube: Get the most out of your 21:9 ultrawide screen. Seamlessly fit 16:9 and 4:3 YouTube videos to 21:9 fullscreen with smart scaling, auto letterbox detection, soft edge blending, and immersive YouTube-styled ambient lighting.

0 (0 reviews)0 (0 reviews)
Download Firefox and get the extension
Download file

Extension Metadata

About this extension
Get the most out of your 21:9 ultrawide display on YouTube. CineCanvas delivers smart aspect ratio scaling, soft edge blending, live ambient glow, customizable side frames, and custom wallpapers — engineered exclusively for YouTube.

  • Optimized for YouTube: CineCanvas is specifically designed and optimized for a flawless ultrawide viewing experience on YouTube.
  • Universal YouTube Integration: Seamlessly works with standard YouTube desktop playback, theater mode, and full-screen view.
  • Direct In-Player Control: Access all mode selections, toggles, and adjustment sliders straight from the embedded player button without needing to open the browser menu.
  • Feature Requests & Feedback: If you have requests for additional features or enhancements, please reach out via email to ship.of.agony.labs@gmail.com.
  • 21:9 Crop: Zooms seamlessly to completely fill your 21:9 ultrawide monitor without distorting the picture.
  • 21:9 Stretch: Expands 16:9 videos horizontally to cover the entire panel.
  • Original (Off): Keeps native aspect ratios untouched.
  • Vivid Ambilight: Maximum luminance and rich, saturated dynamic glow for full ultrawide immersion.
  • Soft Ambient Glow: Milky, diffused background projection reflecting live colors across the side wings.
  • Cinematic Shadow: Subtle edge darkening paired with smooth ambient falloff.
  • Granular Background Blur Slider: Dedicated slider (0px to 80px) accessible directly in the player and popup, ranging from mirror-sharp reflections to deeply blurred velvety auras.
  • GPU-Powered CSS Masking: Utilizes native linear gradient masks directly on the <video> element, avoiding expensive filter bottlenecks.
  • Seamless Inward Fade Slider: Dedicated control (0 to 50) to soften harsh video borders. At 0, edges stay razor-sharp; higher values blend the video naturally into the ambient aura or background.
  • Automatic Pillarbox Boundary Correction: Automatically detects hardcoded black bars in 4:3 streams and positions the soft blend precisely where visible video begins.
  • Seamless Bezel Transition: Smooth slider (0% to 100%) fading outer monitor edges into deep black for a clean transition into physical screen bezels.
  • Intelligent Bar Detection: Scans for black letterbox and pillarbox bars (including hardcoded 4:3 content inside 16:9 containers) and adapts video scaling dynamically.
  • Full 0% to 100% Dimming Slider: Adjust background brightness all the way down to true solid black.
  • Cinema Side Wings (Frames): Replace plain black pillarbox bars with stylized official YouTube badges, pre-saved theater frames (Frame 1 to Frame 5), or upload your own custom high-resolution wallpaper.
  • Independent Presets & Profiles: Slider values for static frames and dynamic Ambilight operate independently — fine-tuning one does not overwrite the other.
  • Dynamic Theme Switching: Supports automatic or manual Dark/Light mode switching.
  • Automatic Language Detection: CineCanvas detects and matches your browser language automatically.
  • 10 Fully Localized Languages: Both the browser popup and the embedded in-player menu are localized in English, German, French, Spanish, Italian, Portuguese, Dutch, Polish, Czech, and Russian (English serves as the default fallback).
  • Alt + C: Cycle through video and ambilight modes.
  • Alt + W: Toggle side wing overlays.
  • Alt + L: Switch wing themes (Dark / Light).
  • Alt + A: Enable or disable automatic letterbox detection.
  • On-Screen Display (OSD): Subtle HUD badges provide immediate visual feedback on keypresses.
  • Completely Free: No paywalls, no subscriptions, no ads.
  • Zero Data Collection: No analytics, no telemetry, no external server requests (data_collection_permissions: none).
  • 100% Local Processing: Color extraction, canvas rendering, and custom background storage operate strictly client-side within your browser.


This project is licensed under the GNU General Public License v3.0.
Rated 0 by 0 reviewers
Log in to rate this extension
There are no ratings yet

Star rating saved

5
0
4
0
3
0
2
0
1
0
No reviews yet
Permissions and data

Required permissions:

  • Access your data for sites in the youtube.com domain

Data collection:

  • The developer says this extension doesn't require data collection.
Learn more
More information
Add-on Links
  • Homepage
  • Support site
  • Support Email
  • Copy add-on ID
Version
0.4.2
Size
10.36 MB
Last updated
4 hours ago (Nov 12, 2026)
Related Categories
  • Appearance
  • Photos, Music & Videos
License
GNU General Public License v3.0 only
Version History
  • See all versions
Tags
  • streaming
  • youtube
  • zoom
Add to collection
Report this add-on
Go to Mozilla's homepage

Add-ons

  • About
  • Firefox Add-ons Blog
  • Extension Workshop
  • Developer Hub
  • Developer Policies
  • Community Blog
  • Forum
  • Report a bug
  • Review Guide

Download

  • Download Firefox
  • Windows
  • macOS
  • iOS
  • Android
  • Linux
  • All

Latest Builds

  • Nightly
  • Beta

Firefox for Business

  • Enterprise

Community

  • Connect
  • Contribute
  • Developer

Follow

  • Instagram
  • YouTube
  • TikTok
  • Bluesky
  • Podcast
  • Privacy
  • Cookies
  • Legal

Except where otherwise noted, content on this site is licensed under the Creative Commons Attribution Share-Alike License v3.0 or any later version.