Clantech v. CoStar & Duolingo: Federal Circuit Affirms Patent Unpatentable
Clantech, Inc. asserted US9892093B1 — covering a hand-held device apparatus for exposing non-standard fonts in network documents to an operating system — against CoStar Realty Information and Duolingo. After 694 days, a Federal Circuit per curiam panel unanimously affirmed the finding of unpatentability, ending Clantech’s enforcement effort at the appellate level.
Federal Circuit closes Clantech’s font-rendering patent appeal unanimously
Clantech, Inc. filed Case No. 24-1361 in the Court of Appeals for the Federal Circuit on 17 January 2024, appealing an adverse ruling on US9892093B1 (application no. US15/197389). The patent covers an apparatus of a hand-held device for exposing non-standard fonts in a network document to an operating system — technology relevant to mobile browsers, document-rendering pipelines, and any application layer that must surface custom typography on constrained devices. The defendants, CoStar Realty Information, Inc. and Duolingo, Inc., were represented by Latham & Watkins LLP.
The Federal Circuit panel — Circuit Judges Lourie, Reyna, and Cunningham — issued a per curiam affirmance on 11 December 2025, 694 days after filing. The basis of termination is recorded as ‘Unpatentable,’ confirming that the claims of US9892093B1 did not survive the validity challenge. An affirmance at this level means the appellate court found no reversible error in the lower tribunal’s patentability determination, leaving the invalidity ruling fully intact and enforceable against Clantech.
A per curiam disposition — issued without a named authoring judge — typically signals that the panel viewed the outcome as legally straightforward, requiring no extended opinion. The 694-day duration is consistent with normal Federal Circuit briefing and argument schedules. What the public record does not reveal is the precise invalidity ground (e.g., anticipation, obviousness, or § 101 subject-matter eligibility) that drove the unpatentability finding, nor whether Clantech pursues any further avenue such as en banc rehearing or certiorari.
Filing to Unpatentable in 694 days
694 days from filing to Federal Circuit affirmance — consistent with standard appellate timelines
Federal Circuit affirms: what the ruling means for both parties
Affirmance means the lower unpatentability ruling stands in full
When the Federal Circuit issues an affirmance, it has reviewed the record and found no reversible legal error in the decision below. The per curiam form — no named authoring judge — suggests the panel considered the outcome legally straightforward. The unpatentability determination against US9892093B1 is now final at this appellate level, with no claims surviving for enforcement.
No reversible error foundClantech’s patent is confirmed unpatentable — enforcement avenue closed
The affirmance extinguishes Clantech’s ability to assert US9892093B1 in its current form. The patent’s claims covering non-standard font rendering on hand-held devices cannot be enforced against CoStar, Duolingo, or any third party going forward. Clantech’s remaining options — en banc petition or Supreme Court certiorari — face a high threshold, and neither stays the effect of the ruling.
Patent unenforceableCoStar and Duolingo win full clearance on the asserted claims
For CoStar Realty Information and Duolingo, the affirmance removes the litigation overhang of US9892093B1 entirely. Both companies — whose products involve network document rendering and text display on mobile devices — can continue product development in this space without exposure to this specific patent. Latham & Watkins’ defence strategy succeeded at both prior and appellate levels.
Full clearance obtainedFont-rendering patent risk in mobile apps reduced — but landscape monitoring warranted
The invalidation of US9892093B1 narrows the assertable patent landscape around non-standard font exposure on hand-held devices. Product teams building mobile document viewers, web renderers, or custom typography engines may treat this outcome as a positive FTO signal for this specific patent. However, related continuations or family members, if any exist, warrant independent monitoring before teams rely on clearance.
Reduced assertion riskFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Clantech, Inc. | Company | Mobile/web font-rendering patent holder — asserting US9892093B1 against technology companiesSearch in Eureka ↗ |
| Defendant | CoStar Realty Information, Inc. | Company | CoStar Realty Information and Duolingo — commercial real estate data and language-learning platformsSearch in Eureka ↗ |
| Co-Defendant | Duolingo, Inc. | Company | Search in Eureka ↗ |
| Plaintiff counsel | James C. Watson | Attorney | Counsel for Clantech, Inc.Search in Eureka ↗ |
| Plaintiff law firm | TraskBritt PC | Law Firm | Representing Clantech, Inc.Search in Eureka ↗ |
| Defendant counsel | Gregory Sobolski | Attorney | Counsel for CoStar Realty Information, Inc.Search in Eureka ↗ |
| Defendant law firm | Latham & Watkins, LLP | Law Firm | Representing CoStar Realty Information, Inc.Search in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | Court of Appeals for the Federal CircuitSearch in Eureka ↗ |
Official order — verbatim text
The per curiam order — ‘AFFIRMED’ — is notably terse, consistent with Federal Circuit practice when a panel unanimously views the patentability question as settled by the record. At the appellate level, affirmance means the court applied the appropriate standard of review — typically substantial evidence for factual findings and de novo for legal conclusions — and found the unpatentability determination below free of reversible error. No new claim construction or invalidity ground is introduced; the lower ruling governs in its entirety.
US9892093B1 — Non-standard font rendering apparatus for hand-held devices
US9892093B1 (application no. US15/197389) covers an apparatus residing on a hand-held device that intercepts or processes network documents — such as web pages — and exposes non-standard or custom fonts contained within those documents to the device’s underlying operating system. The invention addresses a longstanding challenge in mobile browsing: ensuring that custom typography defined in web content is correctly rendered when the OS font stack does not natively include those typefaces. The application’s filing context places it squarely in the era of expanding mobile web consumption and growing reliance on web fonts.
From a competitive standpoint, the patent’s apparatus claims could theoretically apply to any mobile application or browser engine that performs font loading or substitution on behalf of a network document — a description that encompasses a wide range of consumer and enterprise apps. That breadth likely made it commercially attractive for assertion. However, the Federal Circuit’s affirmance of unpatentability removes it from the assertable landscape. For companies developing mobile document viewers, e-reader frameworks, or cross-platform typography engines, the outcome provides a degree of comfort — though independent clearance on related IP remains best practice.
Should you run an FTO against US9892093B1?
Any R&D or product team building mobile applications that render network documents with custom or non-standard fonts — including mobile browsers, document viewers, e-learning platforms, and real estate listing apps — would previously have needed to assess exposure to US9892093B1. Following the Federal Circuit’s affirmance of unpatentability, the granted patent itself no longer presents an enforcement risk. However, teams should confirm whether Clantech holds continuation applications under the same family before treating the field as fully clear.
PatSnap Eureka’s FTO Search Agent can run an automated family search on US15/197389 to surface any surviving continuations, divisionals, or foreign equivalents that share claim scope with the invalidated patent. Eureka can also map the broader font-rendering patent landscape — identifying third-party patents that may cover adjacent apparatus or method claims — so your team can proceed with mobile typography development on a fully informed IP footing.
Run a freedom-to-operate analysis on US9892093B1 to assess your product’s exposure
Run FTO in Eureka →Similar Federal Circuit patent appeals in mobile document-rendering technology
Cases involving software apparatus patent validity challenges at the Federal Circuit, particularly in mobile document rendering and web font technology, follow comparable procedural patterns.
What this case signals for the mobile font-rendering IP landscape
A unanimous Federal Circuit per curiam affirmance of unpatentability carries weight beyond these two defendants — here is what it means for the sector.
Per curiam affirmance signals weak appellate grounds in font-rendering claims
A per curiam ruling typically indicates the panel found the appeal legally uncontroversial. For patent holders in the mobile document-rendering space, this suggests courts are likely to apply searching patentability scrutiny to apparatus claims that route standard OS functionality through a hand-held device intermediary.
Duolingo and CoStar clearance may benefit other defendants in related disputes
With US9892093B1 confirmed unpatentable, any co-pending or related assertion by Clantech relying on the same patent family faces a materially weakened position. Companies that received demand letters or face parallel actions involving this patent number should reassess their exposure and litigation posture promptly.
Clantech v CoStar — key questions answered
The Federal Circuit affirmed the unpatentability of US9892093B1 on 11 December 2025. A per curiam panel of Judges Lourie, Reyna, and Cunningham found no reversible error in the lower invalidity determination, effectively ending Clantech’s ability to enforce the patent against CoStar, Duolingo, or any other party.
US9892093B1 (application US15/197389) covers an apparatus of a hand-held device for exposing non-standard fonts in a network document to an operating system. It targets the technical process by which mobile devices surface custom web typography to the OS font stack. Its breadth across mobile apps handling web content made it a target for assertion against technology companies such as CoStar and Duolingo.
A per curiam affirmance — issued without a named authoring judge — typically signals that the appellate panel considered the outcome legally uncontroversial and required no extended written opinion. In patent appeals, this often suggests the validity challenge was well-grounded and the record strongly supported the lower tribunal’s findings, leaving little room for reversal on the applicable standard of review.
Clantech’s options are limited but not entirely foreclosed. The company could petition for en banc rehearing at the Federal Circuit or seek certiorari at the Supreme Court — both high-threshold avenues with low statistical success rates. Neither petition stays the operative effect of the unpatentability ruling. If Clantech holds continuation applications in the same patent family, those remain unaffected by this specific ruling.
The affirmance of unpatentability for US9892093B1 means the patent cannot be asserted against any party. Companies that received demand letters or are defendants in related proceedings citing this patent number benefit directly. However, the ruling does not automatically invalidate related continuation or divisional applications, so companies should conduct a full patent family search before assuming complete clearance in the non-standard font rendering space.
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