A patentability* search identifies documents which may bar the granting of claims for an invention.

In some cases, claims will have already been prepared. Claims help focus the searcher's attention on the features thought to distinguish the invention from the prior art.

When claims have not been prepared, the searcher uses his judgment, focusing on features which might be claimed.

Providing the searcher with any known prior art, results of prior searches, and names of companies and inventors likely to be active in the field of the invention will help him find the best references.

* also called "novelty" or "pre-examination" or "preliminary" or "pre-ex"

An infringement (or "clearance") search is a thorough search of unexpired patents to locate claims of others which may cover a given product or method. The searcher identifies possibly problematic claims. This enables an attorney to form an opinion on infringement risk, and to advise on claim avoidance.

Sometimes this type of search is called a "right to use" search; that term implies the searcher will review not only active patents, but also expired patents from which one may infer that the invention is in the public domain.

An infringement search may be done early in a product's development, to identify field-dominating patents. However, infringement is often in the details, so one should update the search on the final version of a product before going to market.

A validity search is a thorough patentability search done after a patent has issued to determine whether one or more claims of the patent are valid. The searcher looks for documents more pertinent than those the examiner considered.

Potentially invalidating references may be used

The searcher may also check the maintenance fee status of the patent, do a title search, and determine whether the patent has been involved in litigation.

In a collection search, the searcher reports all patents relating to a specified idea or concept.

A collection search is particularly useful to someone entering a new technical field. The purpose of the patent system is to educate the public, and the existing patents contain a wealth of knowledge from which one can draw. Having a library of the pertinent patents on hand may be very useful during product development, particularly if certain patents are identified as important to patentability or infringement risk.

A state-of-the-art search identifies patents representing major developments in a technology. The searcher typically cites only one of a set of patents having the same teaching, and emphasizes unexpired patents. The goal is to provide a manageable collection of the most pertinent documents.
The Patent and Trademark Office will record documents which affect title to inventions. Recordation is not mandatory, but most assignments are recorded because one effect of recording is to protect the assignee from subsequent transfers of the property by the assignor. Recording ownership by assignment is also a prerequisite to suing for infringement.

A title search identifies all recorded transfers involving a patent. The searcher looks for an identifies any irregularities such as breaks in the chain of title which might indicate legal confusion about who the true owner of the property is.

Whereas a title search is for all documents affecting a single patent, an assignee search identifies all patents which have been assigned to a particular party. Assignee and title searches are commonly done as part of the "due diligence" required before completing a corporate acquisition or merger.