知識社｜冷知識 06｜為什麼 QR Code 一定有三個大方格？ Why Do QR Codes Always Have Three Large Squares?

無論掃描付款碼、登入網站，還是查看餐廳餐牌，你都會看見 QR Code 三個角落的大方格。它們並不是裝飾，而是讓手機能夠快速辨識 QR Code 的重要關鍵。
Every QR Code features three large squares positioned at its corners. They may look like decorative elements, but they are actually essential reference points that allow scanners to recognize and decode the code almost instantly.

中文版本
QR Code 已成為現代生活不可或缺的一部分，從電子支付、產品包裝、活動門票，到網站連結與電子名片，都能看到它的身影。不過，只要仔細觀察，就會發現每一個標準 QR Code 的左上、右上及左下三個角落，都有一個醒目的黑白大方格。很多人以為它們只是設計上的特色，其實它們被稱為「定位標記」（Finder Patterns），是 QR Code 最重要的組成部分之一。QR Code 由日本 Denso Wave 公司於1994年研發，目的就是讓工廠能比傳統條碼更快、更準確地讀取大量資料。工程師發現，如果沒有明確的定位標誌，掃描器便難以判斷 QR Code 的方向、角度及大小，尤其當條碼出現傾斜、旋轉甚至部分遮擋時，更容易發生讀取失敗。因此，他們在三個角落加入大小一致的定位方格，讓掃描器只需找到這三個標記，便能立即計算 QR Code 的位置、旋轉角度及比例，即使倒轉、傾斜或遠近不同，也能迅速完成辨識。除了三個定位標記外，QR Code 內還包含校正線、時序圖案、資料區及錯誤修正碼等不同結構，共同確保資料能正確讀取。其中最令人驚訝的是錯誤修正技術，即使 QR Code 被污漬遮蓋、刮花，甚至缺少部分圖案，只要損毀程度未超出容錯範圍，系統仍然可以成功還原資料。這也是為什麼不少公司會把 Logo 放在 QR Code 中央，看似遮住部分圖案，依然可以正常掃描。今天的 QR Code 已不只是黑白方格，它可以加入不同顏色、圖案甚至品牌設計，但無論如何變化，那三個定位方格幾乎都必須保留，否則大部分掃描器便無法快速辨識。可以說，這三個看似普通的大方格，就是 QR Code 能夠在全球普及的重要原因之一。每當我們用手機掃描一個 QR Code，只需不到一秒鐘便完成辨識，背後其實正是這套精密設計默默發揮作用。

English Version
QR Codes have become an everyday technology, appearing on restaurant menus, payment terminals, event tickets, advertisements, and product packaging around the world. Although most people recognize their distinctive appearance, few realize that the three large squares found in the corners are the key to making the entire system work. These squares are known as finder patterns, and they serve as the scanner’s visual reference points. The QR Code was invented in 1994 by the Japanese company Denso Wave to overcome the limitations of traditional barcodes. Engineers needed a code that could hold far more information while being read quickly from almost any angle. To achieve this, they designed three identical finder patterns in three corners of the code. When a camera captures the image, its software immediately searches for these distinctive squares. Once detected, the scanner can calculate the code’s position, orientation, rotation, and scale in a fraction of a second. Whether the QR Code is tilted, upside down, or viewed from an angle, the finder patterns allow the decoding process to begin almost instantly. The QR Code contains many other sophisticated components as well, including timing patterns, alignment patterns, encoded data, and powerful error-correction algorithms. One of its greatest strengths is its ability to recover information even when part of the code is scratched, dirty, folded, or partially covered. This built-in redundancy is why companies can often place their logos in the center of a QR Code without preventing it from being scanned successfully. Although designers today create colorful, artistic, and highly customized QR Codes, the three finder patterns almost always remain unchanged because they are fundamental to recognition. Without them, most scanners would struggle to identify the code correctly. Every time a smartphone scans a QR Code in less than a second, it is these three simple-looking squares that guide the entire decoding process. They are a perfect example of how thoughtful engineering can make advanced technology feel effortless to millions of users every day.

總評
QR Code 三個大方格並非裝飾，而是整個辨識系統的核心。正因這項巧妙設計，才能讓我們快速、安全地完成每一次掃描。

Summary
The three large squares on every QR Code are far more than a visual trademark. They are the foundation of the technology, enabling fast, accurate scanning in countless situations around the world.