How the QR Code Works
The 1995 patent by Toyota Central R&D Labs that invented the QR code, using three distinct corner squares with a unique 1:1:3:1:1 pixel ratio to let scanners instantly find and read the code from any angle.
Original patent title: “Optically readable two-dimensional code and method and apparatus using the same”
The 1995 patent by Toyota Central R&D Labs that invented the QR code, using three distinct corner squares with a unique 1:1:3:1:1 pixel ratio to let scanners instantly find and read the code from any angle. Granted to Toyota Central R&D Labs Inc in 1998 with 85 claims and 250 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
The patent describes a square two-dimensional barcode containing data cells and three specific positioning symbols at its corners. These positioning symbols consist of concentric black and white squares. When a scanner draws a line through the center of any of these symbols at any angle, it always detects a specific pattern of dark and light widths in a 1:1:3:1:1 ratio. The scanner uses this unique ratio to locate the boundaries and rotational angle of the code. It then uses alternating light and dark timing cells to align its reading grid and decode the data stored in the remaining cells.
The gap
What does this patent NOT cover?
- Does not cover standard one-dimensional barcodes that only store data along a single horizontal axis.
- Does not cover two-dimensional codes that use circular or hexagonal grid layouts instead of a square matrix.
- Does not cover codes that rely on color variations rather than binary dark and light cells to store data.
- Does not cover codes that lack the specific 1:1:3:1:1 ratio positioning symbols at three corners.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The inventors realized that a 1:1:3:1:1 ratio of dark and light areas rarely occurs in printed text or packaging. By placing three squares with this exact ratio in the corners, a scanner can instantly find the code's orientation in a fraction of a second, regardless of rotation.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
QR codes on restaurant tables for digital menus
Boarding passes and concert tickets scanned at gates
Mobile payment codes in apps like WeChat Pay and Venmo
Inventory tracking labels on automotive parts
Why it matters
The bigger picture
This patent laid the foundation for the QR (Quick Response) code, which replaced traditional barcodes in manufacturing and logistics because it could hold vastly more data and be scanned from any angle. Originally designed to track automotive parts in Toyota factories, it became a global standard for mobile payments, digital ticketing, and contactless menus.
Filed
March 14, 1995
Granted
March 10, 1998
Market context
Who's building on this
Companies in this space
Denso Wave, the original developer and a subsidiary of Toyota, remains a key player in industrial scanning. Virtually every modern smartphone manufacturer, including Apple and Samsung, builds native QR code scanning directly into their camera software.
Market impact
By choosing not to enforce their patent rights, Denso Wave allowed the QR code to become an open, globally adopted standard. This decision enabled the rapid rise of mobile-first payment systems in Asia and contactless interactions globally during the COVID-19 pandemic.
Claim 1 — Plain English
What this patent covers
The patent describes a square two-dimensional barcode containing data cells and three specific positioning symbols at its corners. These positioning symbols consist of concentric black and white squares. When a scanner draws a line through the center of any of these symbols at any angle, it always detects a specific pattern of dark and light widths in a 1:1:3:1:1 ratio. The scanner uses this unique ratio to locate the boundaries and rotational angle of the code. It then uses alternating light and dark timing cells to align its reading grid and decode the data stored in the remaining cells.
The clever bit
The inventors realized that a 1:1:3:1:1 ratio of dark and light areas rarely occurs in printed text or packaging. By placing three squares with this exact ratio in the corners, a scanner can instantly find the code's orientation in a fraction of a second, regardless of rotation.
What it does not cover
- Does not cover standard one-dimensional barcodes that only store data along a single horizontal axis.
- Does not cover two-dimensional codes that use circular or hexagonal grid layouts instead of a square matrix.
- Does not cover codes that rely on color variations rather than binary dark and light cells to store data.
- Does not cover codes that lack the specific 1:1:3:1:1 ratio positioning symbols at three corners.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Strong
Citation count
40/40
Highly cited
Claim breadth
20/20
Very broad protection
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$144K – $461K
Midpoint $288K · expired or expiring · industry ×1.6
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
85 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Uchiyama, Y., Watabe, M., Nagaya, T., Nojiri, T., & Hara, M. (1998). How the QR Code Works (U.S. Patent No. 5,726,435). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/5726435/qr-code-two-dimensional-barcode
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How the QR Code Works cover?
The 1995 patent by Toyota Central R&D Labs that invented the QR code, using three distinct corner squares with a unique 1:1:3:1:1 pixel ratio to let scanners instantly find and read the code from any angle.
Who owns patent US 5726435?
Toyota Central R&D Labs Inc owns this patent, granted in 1998.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 5726435 cited by?
This patent has been cited by 250 later patents that build on its ideas.
What problem does this patent solve?
This patent laid the foundation for the QR (Quick Response) code, which replaced traditional barcodes in manufacturing and logistics because it could hold vastly more data and be scanned from any angle. Originally designed to track automotive parts in Toyota factories, it became a global standard for mobile payments, digital ticketing, and contactless menus.
What does this patent NOT cover?
Does not cover standard one-dimensional barcodes that only store data along a single horizontal axis.
Patent monitoring