International Patent Classification: Frequently Asked Questions

The acronym IPC stands for “International Patent Classification”, a hierarchical classification system used primarily to classify and search patent documents (patent applications, specifications of granted patents, utility models, etc.) according to the technical fields they pertain. It serves as an instrument for an orderly arrangement of the patent documents, a basis for selective dissemination of information and a basis for investigating the state of the art in given fields of technology.

(See also the “Guide to the IPC” for more information.)

The Strasbourg Agreement is the legal foundation of the creation and revision of the IPC. On March 24, 1971, a Diplomatic Conference adopted the Strasbourg Agreement Concerning the International Patent Classification (IPC), which on that date was signed by 15 States. Following that, the International (European) Classification of Patents for Inventions became de facto the first edition of the IPC. The Strasbourg Agreement entered into force in 1975. The members to the Strasbourg Agreement constitute the Special Union of the IPC.

(See also a brief Summary of the Strasbourg Agreement for more information.)

The IPC is a very powerful tool for searching patent-related databases. The IPC enables the user to locate the right technology in many types of patent-related searches, or find an informative technology overview or a complete and detailed list of patent documents relating to a specific technology represented by IPC symbols.

Patent offices use the IPC to classify patent applications and to search for the purpose of examination. Anybody involved in research and development, inventing or applying technical solutions can benefit from using the IPC to search patents or patent-related information. Inventors, researchers, teachers, students, lawyers, global companies, SMEs and start-ups may find it very useful.

The number of countries using the IPC when publishing their patent documents is much higher than the number of members of the Strasbourg Union; the IPC is used by patent offices in more than 100 countries in the world. The IPC is, so to speak, the lingua franca of the patent classification.

  • Use of the IPC by industrial property offices [PDF] [DOC]

Detailed information about the IPC can be found on the WIPO IPC website. The site also provides access to the documentation of the IPC revision process, i.e. documents and reports of different meetings of the IPC bodies.

The most comprehensive information about the structure, principles and rules of the IPC is collected in the “Guide to the IPC”. The Guide is the official document approved by the bodies of the Strasbourg Agreement, which explains the use of the IPC. It describes in simple terms and by means of examples the structure and elements of the IPC and how the Classification should be used for classifying or retrieving patent documents. The Guide is revised on a regular basis.

The IPC homepage provides an access to supporting IPC resources such as IPCCAT (IPC Computer-Assisted Categorization), STATS (IPC predictions based on statistical analysis), the IPC Green Inventory (environmentally sound technologies) or IPC training materials. The IPC Publication Help is available in its online publication, with an explanation of its content, navigation, presentation details, search functions, specific notions, e.g. the Revision Concordance List (RCL) or Catchword Index, IPC/CPC/FI parallel viewer or even web services of the IPC. (See also the WIPO technology breakdown/concordance table with links to IPC symbols in “Other resources” under “Intellectual Property Statistics” page.)

The authentic versions of the IPC are English and French. Translations of the IPC are also prepared and published in other languages. For example, the IPC is available in the following languages through the IPC Official Publication’s "bridge" arrow function: Chinese, Czech, Dutch, German, Japanese, Korean, Polish, Portuguese (Brazil), Serbian, Slovak, Spanish, Russian and Ukrainian.

The IPC Official Publication is available online via the IPC homepage as well as in a PDF and other formats for an offline inspection or use. IPC-related files are available in XML, TXT, PDF, etc., on the IPC Download and IT Support Area.

The IPC is periodically revised for improving the system and for reflecting technical developments in its contents. Between 1968 and 2006, the IPC was revised roughly every five years and, after each revision, a new edition was published. The eighth edition of the IPC entered into force on January 1, 2006. Since 2006, the IPC has been revised more frequently and each edition, called also version, is indicated by the year and month of its entry into force. Since 2010, the IPC is revised once a year and each new version enters into force on January 1. Six months in advance, the new scheme, compilation and revision concordance files are available for download or consultation.

The version indicator gives the edition/version where the corresponding entry was introduced in the IPC as a new entry or where its "file scope" was modified, for example [4] or [2008.01]. New entries are progressively introduced in new IPC versions because there are new emerging technologies for which the coverage was not sufficient in the previous versions. In addition, existing classification places can be modified because their original design does not fit the needs of the patent classification. Often, they can be transferred to newly created places where a new, more appropriate classification tree, can be elaborated.

With the reformed IPC, generally, there should be no need to use previous IPC versions for search because a major part of patent files was supposed to be reclassified according to the revision changes. However, in some areas, the reclassification works are delayed, thus it is highly recommended to consider version indicators for IPC-based search and to use the Revision Concordance List to identify relevant IPC symbols for previous IPC versions. Please note the IPC Warnings warning assigned to such places where reclassification has not yet been completed.

(See also paragraphs 8 to 10bis and 42 of the “Guide to the IPC” for more information.)

The classification scheme contains almost 80,000 entries identified by classification symbols that can be allotted to patent documents. These different classification places are arranged in a hierarchical, tree-like structure.

  • The highest hierarchical level are the eight sections of the IPC corresponding to very broad technical fields. For example, Section C deals with "CHEMISTRY” and “METALLURGY".
  • Sections are subdivided into classes, e.g. class C21 deals with the "METALLURGY OF IRON".
  • Classes are further subdivided into subclasses, e.g. subclass A21B deals with "BAKERS' OVENS; MACHINES OR EQUIPMENT FOR BAKING".
  • Subclasses are divided into main groups and subgroups.
  • Main group symbols always end with "/00", e.g. main group A21C 5/00 deals with "Dough-dividing machines".
  • The hierarchy of subgroups under main groups is designated by dots preceding the titles of the groups, e.g. 1-dot subgroup A21C 5/02 deals with “Dough-dividing machines with division boxes and ejection plungers”.

(See also paragraphs 19 to 42 of the “Guide to the IPC” and “Statistics” for more information.)

Definitions are used for clarifying the exact boundaries of the subject matter appropriate for the classification place. They provide additional information in respect of classification entries and serve for their clarification, but do not change the scope of classification entries.

They may consist of six subsections:

  • Definition statement
  • Relationship with other classification places
  • References
  • Special rules of classification
  • Glossary of terms
  • Synonyms and keywords

Definitions are provided only for a limited number of subclasses and groups. In the course of the further development of the IPC, definitions will be elaborated for all its subclasses, and for main groups and subgroups, where appropriate. Definitions are accessible via the Internet publication of the IPC (a definition is available if there is an icon definition shown next to a symbol. See, for example, subclass G01S; by clicking on the definition will open its definition).

(See also paragraphs 44 to 47 of the “Guide to the IPC” for more information.)

The Catchword Index is an alphabetically ordered list of about 20,000 technical terms/keywords in both English and French, which refer to appropriate classification places. It is available online in the IPC Official Publication; it can be browsed or searched.

The German Patent and Trade Mark Office has prepared a more detailed version of a Catchword Index in German and English languages. It offers far more than 100,000 different entries; it is available on the IPC website of the German Patent and Trade Mark Office.

(See also the IPC Publication Help available in the IPC online publication for more information.)

The Revision Concordance List (RCL) shows places where technical subject matter was substantially revised between two consecutive (old and new) IPC versions. It indicates IPC symbols in the new IPC version where the subject matter was moved after deletion or changing scope of places existing in the old IPC version. (See also the IPC Publication Help available in the IPC online publication for more information.)

The Compilation of amendments to the IPC presents all amendments between two consecutive (old and new) IPC versions. It indicates places in the IPC where the title or subject matter was modified and how it was modified with respect to the old IPC version. (See also the IPC Publication Help available in the IPC online publication for more information.)

There are two important classification systems maintained by some of the largest patent offices, namely the European Patent Office (EPO), the United States Patent and Trademark Office (USPTO) and the Japan Patent Office (JPO), i.e. the EPO and USPTO joint Cooperative Patent Classification (CPC) system and the Japanese FI system; both of the two systems are based on the IPC. Using the CPC, a user can carry out a high precision search in the patent documentation classified by the use of this classification system. Using FI/F-term, a user can carry out a high precision search in the Japanese documentation. However, the IPC is used universally all over the world, which enables a user to search, for example, both US and JP documents, or documents published by many other countries using no other classification system than the IPC. Online viewer of both CPC and FI/F-term has been integrated in the IPC Official Publication where they can be displayed in the context of the IPC scheme.