About this extension

This add-on may no longer receive updates, as tab preview is now supported in current versions of Firefox.

What Does the Add-on & CSS Theme Do

With the add-on and the supporting CSS theme, tab preview will appear when a tab is hovered over.

There will be a delay before tab preview shows up. At the same time, if the cursor hovers from one tab over another tab, there’ll be no delay. If the cursor leaves the tab area for a short moment and goes back, the delay will come back. The behaviour is controlled by the CSS theme, user can simply change --preview-delay and --preview-delay-tolerance to adjust the timing.

How to Install the CSS Theme

Go to about:support and locate Profile Folder
Download or copy the CSS theme and move it into Profile Folder -> chrome
Go to about:config and turn toolkit.legacyUserProfileCustomizations.stylesheets to true
Restart Firefox

Compromises

Background image for the browser navbar will be disabled
Incompatible with built-in browser themes “System theme – auto” and “Firefox Alpenglow”
Only the first ten tabs on the left will have tab preview
Adaptive Tab Bar Colour can cause the tab preview to disappear at times, as it resets the browser theme whenever it changes the colour of the tab bar

Supporting CSS Theme

The CSS theme is also available here: download.


/* Tab Preview On Hover supporting CSS theme */

/* Move this file to profile folder > chrome, or append to existing userChrome.css */

/* Version 2024-03-01 */

#navigator-toolbox:-moz-lwtheme {background-image: none !important;
}

#navigator-toolbox {z-index: 10 !important;
}

#tabbrowser-tab-tooltip {display: none !important;
}

.tabbrowser-tab::after {--preview-delay: 1s; /* Delay of tab preview when the cursor move onto a tab from outside of tab bar */
--preview-delay-tolerance: 0.75s; /* Max time period of cursor not hovering on tab bar before preview delay re-engages */
--preview-width: 200px; /* Width of the preview panel */
--preview-height: 150px; /* Height of the preview panel */
}

.tabbrowser-tab::after {box-shadow: 0 0 50px black, 0 0 0 1px var(--arrowpanel-border-color) inset;
outline: 0.5px solid black;
pointer-events: none;
content: "";
display: none;
position: absolute;
z-index: 10000;
top: 50px /* Edit if the preview panel is misplaced */;
width: var(--preview-width);
height: var(--preview-height);
background-color: var(--lwt-accent-color);
background-image: var(--lwt-additional-images);
background-repeat: no-repeat;
background-clip: padding-box;
border-radius: 8px;
}

#tabbrowser-arrowscrollbox:not(:hover) .tabbrowser-tab::after {transition: opacity 0.5s, filter 0s var(--preview-delay-tolerance);
filter: opacity(0);
}

#tabbrowser-arrowscrollbox:hover .tabbrowser-tab::after {transition: opacity 0.5s, filter 0.5s var(--preview-delay);
filter: opacity(1);
}

.tabbrowser-tab:not(:hover)::after {opacity: 0;
}

.tabbrowser-tab:hover::after {opacity: 1;
}

.tabbrowser-tab[selected]:hover::after {opacity: 0;
transition-duration: 0.25s !important;
}

.tabbrowser-tab:nth-of-type(1)::after {display: block;
background-size: cover, 0, 0, 0, 0, 0, 0, 0, 0, 0;
}

.tabbrowser-tab:nth-of-type(2)::after {display: block;
background-size: 0, cover, 0, 0, 0, 0, 0, 0, 0, 0;
}

.tabbrowser-tab:nth-of-type(3)::after {display: block;
background-size: 0, 0, cover, 0, 0, 0, 0, 0, 0, 0;
}

.tabbrowser-tab:nth-of-type(4)::after {display: block;
background-size: 0, 0, 0, cover, 0, 0, 0, 0, 0, 0;
}

.tabbrowser-tab:nth-of-type(5)::after {display: block;
background-size: 0, 0, 0, 0, cover, 0, 0, 0, 0, 0;
}

.tabbrowser-tab:nth-of-type(6)::after {display: block;
background-size: 0, 0, 0, 0, 0, cover, 0, 0, 0, 0;
}

.tabbrowser-tab:nth-of-type(7)::after {display: block;
background-size: 0, 0, 0, 0, 0, 0, cover, 0, 0, 0;
}

.tabbrowser-tab:nth-of-type(8)::after {display: block;
background-size: 0, 0, 0, 0, 0, 0, 0, cover, 0, 0;
}

.tabbrowser-tab:nth-of-type(9)::after {display: block;
background-size: 0, 0, 0, 0, 0, 0, 0, 0, cover, 0;
}

.tabbrowser-tab:nth-of-type(10)::after {display: block;
background-size: 0, 0, 0, 0, 0, 0, 0, 0, 0, cover;
}

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