Highlight Opened Tabs EN

Highlight Opened Tabs is a lightweight Firefox extension that helps you see which pages are already open. Hover a link on any page and tabs with the same address are highlighted in your tab strip, while the link itself can be marked right on the page. Duplicates of the active tab are highlighted too, so you can avoid opening the same page twice.

Highlight opened tabs on hover
Hover any link on a webpage – tabs with the same URL are selected in your tab strip. The hover delay is adjustable, and highlights can be cleared automatically when the cursor leaves the page, or kept while you move to the tab bar or side panel.

On‑page link highlight
When the hovered link is already open in another tab, it is marked right on the page. Combine any of three styles:
- Card frame – a thin frame around the result block, with adjustable border width
- Link underline – a line under each line of link text, with adjustable thickness
- Soft glow – a gentle outer glow around the link or card, with adjustable strength and ring width

Pick a general color from 10 presets or any custom color, override the color for each style, and reset any setting to its default with one click. Show the on‑page highlight whenever a duplicate exists, or only when the matching tabs are hidden – handy with extensions that hide tabs, such as Workspaces.

Highlight duplicates of the active tab
When you switch to or load a tab, other tabs with the same normalized URL are briefly highlighted, and the flash duration is adjustable. An optional badge counter on the toolbar icon shows how many copies are open. Matching ignores “www.”, trailing slashes, parameter order and tracking parameters (utm_*, fbclid, gclid and similar), and recognizes the same YouTube video across youtube.com and youtu.be links.

Site access under your control
On‑page highlighting needs access to websites. If access is off – for example, switched off in about:addons – the extension shows a clear banner and a “!” on its icon with a one‑click Grant access button. You can also choose to use it without page highlighting: tab‑strip features keep working.

Language selection
Follow the browser language automatically or pick any of the 19 interface languages in the settings.

Technical details
- Built on Manifest V3
- Uses a lightweight content script and event‑based background logic
- Settings are stored locally – no data collection, tracking, or analytics

Localization
The extension is fully translated into 19 languages, including:
English, Spanish, German, French, Russian, Belarusian, Chinese (Simplified and Traditional), Japanese, Portuguese, Italian, Korean, Polish, Dutch, Turkish, Ukrainian, Indonesian, Arabic, and Vietnamese.

Source
https://github.com/Kustrica/HighlightOpenedTabs