Subject matter eligibility under § 101
Section 101 defines what kinds of inventions can be patented. The statute is broad on its face, but the Supreme Court has long held that laws of nature, natural phenomena, and abstract ideas lie outside the categories of patent-eligible subject matter. The two-step framework synthesized in Mayo and Alice now governs every § 101 inquiry, and it has become the most volatile and contested doctrine in modern patent law.
The rule
A claim is patent-eligible under § 101 only if it is directed to a process, machine, manufacture, or composition of matter that is not, in substance, a law of nature, a natural phenomenon, or an abstract idea. Under the two-step framework set out in Mayo Collaborative Services v. Prometheus Laboratories, Inc., 566 U.S. 66 (2012), and reaffirmed in Alice Corp. v. CLS Bank International, 573 U.S. 208 (2014), a court first asks whether the claim is "directed to" one of the three judicial exceptions; if so, it then asks whether the claim's additional elements supply an "inventive concept" that transforms the ineligible concept into a patent-eligible application.
The exceptions are not statutory. They are judge-made, grounded in the long-standing concern that monopolies on the basic tools of scientific and technological work would impede rather than promote progress. The result is that § 101 operates not as a positive grant of authority but as a screen, applied at the threshold of validity, that can defeat a claim before any inquiry into anticipation, obviousness, or written description and enablement.
Statutory and constitutional source
Section 101 of the Patent Act provides: "Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefor, subject to the conditions and requirements of this title." 35 U.S.C. § 101. The four enumerated categories — process, machine, manufacture, composition of matter — have been treated as expansive. In Diamond v. Chakrabarty, 447 U.S. 303 (1980), the Court held that a genetically engineered, oil-eating bacterium was patentable as a "manufacture" or "composition of matter," and described the statutory scope as covering "anything under the sun that is made by man," subject to the three exceptions.
The constitutional grounding is Article I, Section 8, Clause 8, the Patent and Copyright Clause, which empowers Congress "to promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries." The Court has read this clause as a constraint on what Congress may patent, and the judicial exceptions to § 101 are framed as an effort to keep the patent system within that constitutional purpose. See Bilski v. Kappos, 561 U.S. 593 (2010); Mayo, 566 U.S. at 71–72.
The framework the courts apply
Although the modern test crystallized in 2012 and 2014, its lineage runs through Gottschalk v. Benson, 409 U.S. 63 (1972), Parker v. Flook, 437 U.S. 584 (1978), and Diamond v. Diehr, 450 U.S. 175 (1981). In Diehr the Court upheld a process for curing rubber that incorporated the Arrhenius equation, holding that a claim does not become ineligible merely because it employs a mathematical formula. In Bilski the Court rejected the Federal Circuit's "machine-or-transformation" test as the sole measure of process eligibility and invalidated claims to a method of hedging risk, reasoning that the claimed process recited an abstract idea.
Step one: "directed to" an exception
The first step asks whether the claim is "directed to" a law of nature, a natural phenomenon, or an abstract idea. The inquiry is one of characterization. Courts examine the claim "as a whole" and identify its "focus" or "character." See Enfish, LLC v. Microsoft Corp., 822 F.3d 1327 (Fed. Cir. 2016). In Enfish, the Federal Circuit held that claims to a self-referential database table were not directed to an abstract idea at step one because they recited a specific improvement to the way computers store and retrieve data, not a generic invocation of computers to implement a longstanding business practice.
By contrast, claims that invoke a computer only to apply a familiar economic or organizational practice are typically deemed directed to an abstract idea. Alice itself involved claims to a computerized scheme for mitigating settlement risk in financial transactions; the Court held that such intermediated settlement was a "fundamental economic practice long prevalent in our system of commerce" and therefore an abstract idea.
Step two: the "inventive concept"
If the claim is directed to an exception, step two asks whether the claim's elements, considered individually and as an ordered combination, "transform the nature of the claim" into a patent-eligible application — that is, whether they supply an "inventive concept." Alice, 573 U.S. at 217–18; Mayo, 566 U.S. at 72–73. Generic computer implementation, recitation of conventional steps at a high level of generality, or appending the words "apply it" to an abstract idea will not satisfy step two.
In McRO, Inc. v. Bandai Namco Games America Inc., 837 F.3d 1299 (Fed. Cir. 2016), the Federal Circuit upheld claims to rules-based lip synchronization for animated characters, reasoning that the claims used a combined order of specific rules to render information into a specific format and produced an improvement over prior animation methods. McRO illustrates that a sufficiently specific algorithmic improvement can carry a claim past step two even when the claim concerns software.
The Federal Circuit's later decisions in Berkheimer v. HP Inc., 881 F.3d 1360 (Fed. Cir. 2018), and Aatrix Software, Inc. v. Green Shades Software, Inc., 882 F.3d 1121 (Fed. Cir. 2018), held that the question whether a claim element or combination is "well-understood, routine, and conventional" is a question of fact, not pure law. Where that factual question is genuinely disputed and material to the step-two analysis, summary judgment or dismissal under § 101 is improper.
The natural-phenomenon and law-of-nature exceptions
The same two-step framework governs claims drawn to laws of nature and natural phenomena, with results that have been particularly difficult for the life sciences. In Mayo, the Court invalidated claims that correlated metabolite levels with drug efficacy, holding that the underlying correlation was a law of nature and that the claimed steps of administering, determining, and adjusting added nothing inventive. In Association for Molecular Pathology v. Myriad Genetics, Inc., 569 U.S. 576 (2013), the Court held that isolated naturally occurring DNA segments are products of nature and not patent-eligible, while complementary DNA (cDNA) is eligible because it is not naturally occurring.
Burden and proof
Issued patents are presumed valid under 35 U.S.C. § 282(a), and an accused infringer must prove invalidity by clear and convincing evidence. Microsoft Corp. v. i4i Limited Partnership, 564 U.S. 91 (2011). That presumption applies to § 101 challenges as well, but it interacts awkwardly with the doctrine because eligibility is treated as a question of law that may rest on underlying questions of fact. Berkheimer, 881 F.3d at 1365.
Where eligibility can be decided without resolving any disputed historical fact — for example, where the patent's specification itself concedes that the additional elements were conventional — courts decide § 101 as a matter of law and the clear-and-convincing standard does not meaningfully bear on the result. Where the conventional-or-not question is contested with record evidence, the standard becomes more important, and dismissal at the pleading stage will often be unavailable. The doctrine accordingly has a procedural posture that differs from other invalidity defenses: it is frequently raised on a motion to dismiss under Rule 12(b)(6) or on early summary judgment, and the Federal Circuit has repeatedly cautioned that such early disposition is appropriate only when the patent's intrinsic record resolves the dispositive factual issues.
Interaction with related doctrines
Because § 101 is a threshold validity inquiry, its operation overlaps and sometimes collides with other doctrines. The Court in Mayo rejected the argument that novelty and nonobviousness analyses should be folded into eligibility, but the step-two question whether claim elements are "well-understood, routine, and conventional" plainly resembles the inquiry that § 102 and § 103 address. The Federal Circuit has insisted that § 101 is not a substitute for anticipation or obviousness, but the conceptual overlap is real and unresolved.
Section 101 also intersects with claim construction. The eligibility analysis depends on what the claim covers, and the Federal Circuit has at times resolved § 101 disputes by reference to the construction of disputed terms. See, e.g., Aatrix, 882 F.3d at 1125. Where construction is necessary to resolve eligibility, courts ordinarily defer the § 101 ruling until after a Markman hearing.
A further interaction arises with enablement and written description under § 112. Functional claims that the Federal Circuit has invalidated under § 101 often raise § 112 concerns as well, particularly where the claim attempts to capture a result without disclosing how to achieve it.
Practical notes
Section 101 is most often raised at the pleadings stage by motion to dismiss or judgment on the pleadings, and on early motions for summary judgment. The defense is attractive to accused infringers because, when granted, it disposes of the case before the expense of discovery and claim construction. District courts in software-heavy jurisdictions handle § 101 motions frequently; Eastern District of Texas, Western District of Texas, Delaware, and Northern District of California dockets contain a steady stream of opinions applying the framework.
The Federal Circuit reviews § 101 determinations de novo, with underlying factual findings reviewed for clear error. The PTAB does not have authority to institute inter partes review on § 101 grounds, but eligibility may be raised in post-grant review within nine months of issuance. The U.S. Patent and Trademark Office issues subject-matter eligibility guidance that examiners follow during prosecution; that guidance does not bind the courts but shapes the prosecution record and may influence litigation positions.
Drafting practice has adapted to the doctrine. Specifications now commonly emphasize specific technological problems and concrete improvements, and claims frequently recite tangible outputs and specific algorithmic operations. Whether such drafting choices alter outcomes turns on the same fact-intensive characterization questions that the framework leaves unresolved.
Open questions
The state of § 101 doctrine is unsettled. The Federal Circuit's decisions are difficult to reconcile across technology areas; panels have reached divergent conclusions on facially similar claims. The Supreme Court has repeatedly declined to revisit Alice, including denying certiorari in cases that the Solicitor General urged it to take. Congress has held hearings on potential statutory reform, but no enacted legislation has emerged. The Federal Circuit has acknowledged the difficulty publicly, and several judges have called for clarification.
Open questions include the proper level of generality at which to characterize a claim at step one; the relationship between the conventional-or-not factual inquiry and the legal question of eligibility; the application of the framework to diagnostic claims after Mayo and Myriad; and whether the judicial exceptions are constitutionally compelled or merely a long-standing gloss that Congress could displace. Practitioners should expect continued instability and pay close attention to panel composition, the technology at issue, and the procedural posture of any § 101 ruling.
See also
- Alice Corp. v. CLS Bank InternationalThe 2014 Supreme Court decision that established the modern two-step framework.
- Anticipation under § 102A separate validity doctrine sometimes confused with the inventive-concept inquiry.
- Obviousness under § 103Distinct from § 101 but raises similar questions about routine and conventional elements.
- Written description and enablementFunctional claims often raise both § 101 and § 112 concerns.
- Claim constructionEligibility frequently turns on the scope a court gives the claim.
- Post-grant reviewThe only PTAB proceeding in which § 101 may be raised.
Last reviewed: 2026