Patent Classification Explorer
Browse, compare and understand IPC and CPC patent classification codes. Navigate hierarchies, switch between systems, and explore differences.
254,249
CPC Classifications
80,145
IPC Classifications
21,361
Catchword Keywords
What Is the Patent Classification Explorer?
The Patent Classification Explorer is a free tool for navigating the two major patent classification systems used worldwide: the International Patent Classification (IPC) maintained by WIPO, and the Cooperative Patent Classification (CPC) jointly managed by the EPO and USPTO.
Patent classification codes organize every area of technology into a structured hierarchy – from broad sections like “Electricity” or “Chemistry” down to highly specific subgroups. They are essential for patent searching, prior art analysis, and technology landscaping.
With this tool you can browse the full IPC and CPC hierarchies, switch between systems for the same code, and use the Diff view to see exactly where the two systems diverge. Every page includes details like code descriptions, hierarchy context, and cross-system mappings.
Sections
A
Human Necessities
9,906 IPC 29,967 CPC
B
Performing Operations; Transporting
18,398 IPC 56,958 CPC
C
Chemistry; Metallurgy
15,230 IPC 38,319 CPC
D
Textiles; Paper
3,301 IPC 5,692 CPC
E
Fixed Constructions
3,485 IPC 9,270 CPC
F
Mechanical Engineering; Lighting; Heating; Weapons; Blasting
9,609 IPC 28,141 CPC
G
Physics
9,601 IPC 38,254 CPC
H
Electricity
10,615 IPC 32,161 CPC
Y
Emerging Cross-Sectional Technologies
15,487 CPC CPC only
Patent Insights
Explore global patent filing data, top applicants, and trending technology areas.
Frequently Asked Questions
What is the International Patent Classification (IPC)?
The IPC is a hierarchical classification system maintained by the World Intellectual Property Organization (WIPO). It divides all technology into eight sections (A–H) and further subdivides them into classes, subclasses, main groups and subgroups. Patent offices worldwide use the IPC to organize and retrieve patent documents.
What is the Cooperative Patent Classification (CPC)?
The CPC is a jointly managed extension of the IPC, developed by the European Patent Office (EPO) and the United States Patent and Trademark Office (USPTO). It uses the same top-level structure as the IPC but adds significantly more detail – over 250,000 entries compared to roughly 80,000 in the IPC – plus an additional section Y for emerging cross-sectional technologies.
What is the difference between IPC and CPC?
Both systems share the same hierarchical structure (section → class → subclass → group → subgroup), but the CPC is more granular. The CPC builds on the IPC structure, covers nearly all of it and adds further subdivisions for finer categorization. It also introduces section Y for cross-cutting themes like climate-change mitigation. Use the Diff view on this site to see exactly where the two systems diverge, or read the full guide: IPC vs CPC: the key differences.
How do I read a patent classification code?
A code like H04L 9/32 breaks down as follows: H = section (Electricity), H04 = class (Electric Communication Technique), H04L = subclass (Transmission of Digital Information), 9/00 = main group (Cryptographic mechanisms), 9/32 = subgroup (including means for verifying identity). Codes read left to right from broadest to most specific. The full walkthrough: How to read patent classification codes.
How do I find the classification code for my invention?
Describe your technology in plain language on the AI Classification Suggest page and it returns matching IPC and CPC codes with explanations. Alternatively, browse from a section page down the hierarchy, or search codes and keywords directly.
Can a patent have multiple classification codes?
Yes, and most do. A patent receives one first classification for the core invention plus additional codes for its other technical aspects. In the CPC, codes are further marked as inventive or additional information.
What is the classification code for machine learning and AI?
Machine learning is classified under G06N 20/00. The surrounding subclass G06N covers computing arrangements based on specific computational models, including neural networks and other AI approaches. The CPC subdivides this area much deeper than the IPC. See the topic overview: AI and machine learning patent classification.
Are kind codes like A1 or B1 classification codes?
No. Kind codes such as A1 or B1 describe the publication stage of a document, for example an application versus a granted patent. Classification codes like H04L 9/32 describe the technical content. The two appear together on patent documents but are independent systems.
What do sections, classes, subclasses, main groups and subgroups mean?
These are the five levels of the hierarchy. Sections (A–H, plus Y in CPC) are the broadest groupings. Classes (e.g. H04) narrow the topic. Subclasses (e.g. H04L) specify a field within the class. Main groups (e.g. H04L 9/00) define a broad subject, and subgroups (e.g. H04L 9/32) provide the most specific categorization.
What does "Not Allocatable" mean in CPC?
A CPC code marked Not Allocatable is a structural placeholder that exists only to organize the hierarchy. Patents cannot be classified under it directly – you must use one of its more specific child codes instead.
What does "Additional Only" mean in CPC?
A CPC code marked Additional Only can only be used as a secondary (additional) classification. It cannot serve as the primary classification for a patent document. These codes typically capture auxiliary aspects of an invention.
What is the Y section in CPC?
Section Y is unique to the CPC and covers emerging cross-sectional technologies. It includes codes for topics like climate change mitigation (Y02) and information or communication technologies with potential sustainability impact (Y04). There is no equivalent in the IPC.
What is the /00 convention?
A subgroup number ending in /00 denotes a main group – the top-level entry under a subclass. All other subgroup numbers (e.g. /02, /32) represent progressively more specific subdivisions of that main group.
How does the Diff view work?
The Diff view compares a classification code’s children in both IPC and CPC side by side. Entries are color-coded: codes that exist in both systems are neutral, codes only in CPC are highlighted in blue, and codes only in IPC are highlighted in amber. This makes it easy to spot where the CPC adds extra detail.
Where does the data come from?
How often is the data updated?
The data reflects the latest available IPC and CPC release 2026.01. Updates are performed periodically as new revisions become available, typically every few months.
What changed in the latest IPC revision?
The IPC Changelog shows all codes that were created or deleted between IPC versions. The current revision (2025.01 → 2026.01) includes hundreds of classification changes across multiple revision projects.
How many classification codes are there?
The IPC contains roughly 80,145 entries and the CPC contains roughly 254,249 entries. The exact count changes with each revision as codes are added, deprecated or reclassified.
Is this tool free to use?
Yes. The Patent Classification Explorer is a free, open resource. The underlying classification data is published under the CC BY 4.0 license by WIPO and the EPO/USPTO.