Broadest reasonable interpretation, usually abbreviated BRI, is the claim-construction standard the U.S. Patent and Trademark Office applies while a patent application is still pending. The rule appears in the Manual of Patent Examining Procedure (MPEP) § 2111, which instructs examiners that pending claims "must be 'given their broadest reasonable interpretation consistent with the specification.'" The standard is deliberately broad: it directs the examiner to read a claim term as widely as the words reasonably allow, so long as the reading remains consistent with the specification and with how a person of ordinary skill in the art would understand it.

The rationale is procedural. During prosecution the applicant can still amend the claims, so reading them broadly serves to flush out ambiguity and ensure the examiner tests the claims against the full scope of relevant prior art before the patent issues. A claim construed broadly captures more potential prior art, which in turn forces the applicant to narrow or clarify language before the claim becomes a fixed, issued right.

"During patent examination, the pending claims must be “given their broadest reasonable interpretation consistent with the specification.”"— USPTO, MPEP § 2111, source

Broad, but not unbounded

BRI is not a license to read claims unreasonably. MPEP 2111 anchors the standard to the specification, citing the Federal Circuit's en banc decision in Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005), which it quotes for the proposition that the Office "determines the scope of claims in patent applications not solely on the basis of the claim language, but upon giving claims their broadest reasonable construction 'in light of the specification as it would be interpreted by one of ordinary skill in the art.'" An interpretation that is broad but inconsistent with the specification, or that a skilled artisan would not adopt, is not a permissible broadest reasonable interpretation.

The standard has practical consequences for how claim terms are drafted. A functional term such as the "mesh routing module configured to receive a first packet" recited in U.S. Patent No. 9,479,428 would, during examination, be read by the examiner as broadly as the specification reasonably supports — potentially reaching software or hardware implementations — unless the applicant defined the term more narrowly or amended to limit it. Applicants frequently act as their own lexicographers in the specification precisely to constrain the breadth an examiner can give a term under BRI.

How BRI differs from court construction

The most consequential point about BRI is that it is not the standard courts use for issued patents. In litigation, a district court construes an issued claim under the Phillips framework, seeking the meaning the term would have to a person of ordinary skill in the art at the time of the invention, informed by the intrinsic record. That inquiry seeks the correct construction, not the broadest reasonable one. Because an issued claim can no longer be amended, courts do not apply the deliberately expansive BRI reading used during examination.

This divergence once extended to the Patent Trial and Appeal Board. For years the PTAB applied BRI in inter partes review and other America Invents Act proceedings, a practice the Supreme Court upheld in Cuozzo Speed Technologies, LLC v. Lee (2016). The USPTO later changed course by rule: for AIA petitions filed on or after November 13, 2018, the Board construes claims under the same Phillips-type standard used in district court, narrowing the gap between agency and court construction in those proceedings. BRI, however, remains the governing standard for ordinary examination of pending applications — the context MPEP 2111 addresses.

For applicants and challengers alike, the takeaway is that the same words can be read differently depending on the forum and the procedural posture. A term given a broad reading by an examiner under BRI may be construed more narrowly by a court once the patent has issued, and the prosecution record generated under the broad standard becomes part of the intrinsic evidence a court later consults.

Why the standard exists and where it bites

The justification for BRI is rooted in the dynamics of examination. Because claims remain amendable during prosecution, giving them their broadest reasonable reading reduces the chance that an ambiguous term will later be asserted more broadly than the examiner anticipated. The Federal Circuit has explained that the approach serves the public by encouraging applicants to draft claims precisely and to remove ambiguity before the patent issues, when amendment is still possible and the public has not yet relied on a fixed claim scope.

BRI most often bites in the prior-art context. A term read at its broadest reasonable scope captures a wider range of references, so an examiner applying BRI may reject a claim over art that a narrower, litigation-style construction would not reach. The applicant's options are to argue that the examiner's reading is not reasonable in light of the specification, to amend the claim to narrow it, or to define the term expressly. Each path leaves a mark on the prosecution history that can later constrain the claim in court.

That last point connects examination back to litigation. Statements an applicant makes to overcome a BRI-based rejection — distinguishing prior art, disclaiming scope, or defining a term — become part of the intrinsic record. When a district court later construes the issued claim under Phillips, those prosecution statements can narrow the term, sometimes decisively. The broad reading applied during examination thus shapes the narrower reading a court later adopts, which is why prosecution conduct under BRI has consequences well beyond the grant of the patent.