Google Search Centered (Firefox)

Centers Google's search UI on wide screens.

On big monitors Google pins the search results column, the search box and the filter-tabs row (AI Mode / All / Images / ...) to the LEFT zone of its CSS grids, even when the right side of the page is empty. This add-on centers three elements on the viewport center:

1. the results column (#center_col) — spans the full grid row (grid-column: 1 / -1) and centers with auto margins;
2. the search bar pill;
3. the filter tabs row (All / Images / Videos / ...);
4. the AI overview panel ("AI Overview" / "Visão geral criada por IA"), when the page has one.

Items 2 and 3 are shifted with transform: translateX(delta) where delta is derived at runtime from each element's untransformed baseline — nothing is hardcoded, so any viewport width between (or beyond) the tested sizes stays correct. A live overlap guard drops the shifting when a centered item would collide with the header controls (Settings / Apps / Sign in); at those widths the native layout is kept.

What it does

        NATIVE LAYOUT                        WITH THIS ADD-ON
┌───────────────────────────────┐    ┌───────────────────────────────┐
│ ▓▓  ▄▄▄▄▄▄▄▄▄▄▄▄▄       ░░ ░░  │    │       ░░  ▄▄▄▄▄▄▄▄▄▄▄▄▄ ▓▓    │
│ ───────────────────────       │    │     ───────────────────────   │
│ ██████                        │    │            ██████             │
│ ██████    (empty space)       │    │            ██████             │
│ ██████                        │    │            ██████             │
└───────────────────────────────┘    └───────────────────────────────┘
   results, search bar and              all three sit on the viewport
   tabs hug the left edge               center, aligned with each other

▓▓ logo   ▄▄ search bar   ── filter tabs   ██ results   ░░ header controls

It only kicks in when:

• the window is at least 1440px wide (one knob, MIN_WIDTH in content.js), and
• no knowledge panel (#rhs) is visible — when Google shows one, the add-on leaves the original layout untouched.

Works on google.com and regional Google domains (see the matches list in manifest.json; add your country TLD there if it is missing).

Install (temporary, for development / personal use)

1. Open Firefox and go to about:debugging#/runtime/this-firefox
2. Click Load Temporary Add-on…
3. Select manifest.json from this folder

The add-on stays active until Firefox is closed.

Install (permanent — signed release)

Every release ships a Mozilla-signed .xpi that installs permanently in any Firefox (release channel):

1. Download the signed .xpi (google-search-centered-<version>.xpi) from the latest release
2. In Firefox: about:addons → gear icon → Install Add-on From File… → pick the file (or just drag the file into the Firefox window)

To sign your own builds instead:

npx web-ext sign --source-dir . --api-key=<JWT issuer> --api-secret=<secret> --channel unlisted

(AMO developer credentials: https://addons.mozilla.org/developers/addon/api/key/)

Verified behavior (Firefox 151, Sep 2026 — measured live in the browser)

Window	client width	column	pill	tabs
2560x1440 (full)	2548	centered	centered	centered
1920x1080 (full)	1908	centered	centered	centered
1600	1588	centered	centered	centered
1440x900	1428	centered	centered	centered
1280 (2560 half)	1268	native	native	native
960 (1920 half)	948	native	native	native
any width + knowledge panel	—	native	native	native

All centered states land within ±1px of clientWidth / 2, with zero horizontal overflow, and re-center correctly when the window is resized in either direction (including across the 1440px threshold). Larger monitors (4K etc.) use the same live math and need no changes.

Customization

• MIN_WIDTH in content.js — threshold (px) above which centering applies.
• Results column width and all offsets are captured from the live page.

Notes

• Google renders the tabs strip differently per locale/layout (en-US uses a role="navigation" wrapper; pt-BR 2026 renders div-based tabs in a different container). The add-on locates the strip by tab-label text and centers the label row plus its clip/fade frame, so both variants work.
• tools/ contains Marionette probe scripts that can inspect and measure a live Firefox window (used to verify against the real browser).

Screenshots

• screenshots/before.png — native 2560px layout (column at 9% of the width)
• screenshots/after.png — with the add-on: pill, tabs and results centered