Patent Classification Systems

Below are some of the various schemes historically used or currently used to classify patents. With literally millions of patents, having some sort of classification or organization is a good thing. It's generally useful to be able do searches for patents within a particular class. In theory similar patents should be assigned similar classifications. For extra fun I've added a power search that lets you search the five systems below from that single page.

US Patent Office's Classification System

ccl or USPC is the uspto's original patent classification system which is apparently being phased out through no fault of my own. (They will still be used for design and plant patents so they won't go away entirely.)
  1. Try the beta ccl search! Enter strings to look for in ccl subclass definitions and then search for corresponding patents and/or patent applications.

  2. Display a ccl subclass' details and generate a search for it.

  3. Check out my spin on the NBER's (National Bureau of Economic Research) aggregation of the patent office's classifications.

  4. Class listings

Great Britain Design Classification System

  1. Try the beta classification search!

  2. Class listings

  3. Collapsed listing

  4. Subclass counts

Canadian Patent Classification System

This system was phased out late in 1989 and was what the original cpc acronym stood for.
  1. Here is a Canadian Patent Classification search you can use. It still is relevant on the Canadian Patent Office's web site to find older patents classified under this system.

  2. (Corrected Link) Display a cpc subclass' details and generates a CIPO (Canadian Intellectual Property Office) search for it!

  3. Also available are Canadian class listings.

International Patent Classification

Updated for 2019!
  1. See fun ipc statistics

  2. Try the beta ipc search! Enter strings to look for in ipc subclass definitions and then search for corresponding patents and/or patent applications at the uspto.

  3. Display an ipc subclass' details and generate a CIPO search for it.

Cooperative Patent Classification

Updated for 2020.08

This is the world's newfangled way of classifying patents. Most countries on the planet have adopted it. Here are tools to help you navigate the twisty passages.
  1. See fun cpc statistics

  2. Try the beta cpc search! Enter strings to look for in cpc classifications and then search for corresponding US patents and/or US patent applications.

  3. Display a cpc classification's details and generate a uspto search for it.

  4. Check out this page of patents I've come across without cpcs. The USPTO was supposed to assign cpcs to all utility patent however they missed a few. The uspto makes available a bulk file of cpcs for utility patents as well as a list of withdrawn patents. It's a relatively easy programming task to find the 9,615 utility patents not in the bulk cpc file that weren't withdrawn patents.

  5. No one believes me, but I found that over 50% of US Plant Patents have cpc assignments. Also, as far as I know, there is no bulk source for this data. The bulk cpc data file that is available only contains assignments for utility patents. Bulk CPC assignments for reissued patents apparently aren't available either.

  6. I just loaded 2020.08 which replaced 2019.02 here on my site (I missed a few updates in between). In comparing the plant cpcs just mentioned against 2020.08, I see plant patents with cpc assignments that are no longer valid (the assigned cpc no longer exists in 2020.08). There could be more orphaned cpc assignments, these were found by comparing the plant cpc assignments I have on hand. The orphaned classifications would be easier to find if only, say it with me, there was a bulk source of cpc assignments for non utility patents.

    Orphaned cpc assignments in patft
    A01H5/0222
    Y02E50/17
    Y02P60/247


  7. Add cpc-based searches to your browser's tool bar! Then when you are viewing a page with a cpc classification highlight it and then press one of the bookmarklets in your tool bar to see corresponding applications or patents.

    Try it out here. Highlight the A61K 35/65 and press either bookmarket in your toolbar
    A61K 35/65. . Amphibians, e.g. toads, frogs, salamanders or newts

    Note that the highlighting can be done while viewing a cpc scheme page or an ordinary one like this one!
    Important note: The buttons would break (stop working) if the uspto changes or replaces patft and appft so no warranty is expressed or implied!

    Windows: One-time instructions to load these searches to your tool bar

    Hover over each of these links. Hold down the left mouse button and drag (while still holding down left mouse button) each link to your browsers tool bar (then release the left mouse button): cpc apps cpc patents

    Here's how the bookmarklets look in firefox

    Note that the links need to be dragged individually to your tool bar. This is a one time step up.

    iPad: One time instructions for a Safari tool bar

    It's slightly more work on an iPad but is possible! There is some one time setup: You'll need to enable a tool bar in Safari. Go to "Settings" and tap on "Safari." Set Show Favorites Bar to "ON." Tap "Advanced" and set JavaScript to "ON." Then just repeat this for each bookmark:
    1. Create a bookmark - name it cpc apps and set the location to Favorites
    2. Then Edit the bookmark and delete the url and paste in the javascript block below
    Repeat for cpc patents. This youtube video makes it look easy!

    Here is the block of javascript for the cpc apps link:
    javascript:(function(){q=(document.getSelection()+'').trim().replace(/%20/,'');window.location.href='http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=0&f=S&l=50&d=PG01&Query=CPC%2F%22'+q+'%22%2F';})()
    
    Here is the block of javascript for the cpc patents link:
    javascript:(function(){q=(document.getSelection()+'').trim().replace(/%20/,'');window.location.href='http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&p=1&u=%2Fnetahtml%2Fsearch-bool.html&r=0&f=S&l=50&TERM1='+q+'&FIELD1=CPC&d=pall';})()
    

Classification Case Study