Trademark Infringement and the Likelihood of Confusion Test: How Courts Decide Whether One Mark Infringes Another

By Hank FasthoffJuly 7, 2026

Trademark infringement occurs when someone uses a mark in commerce that's likely to cause confusion among consumers about the source, sponsorship, or affiliation of goods or services. Under the Lanham Act, a plaintiff asserting trademark infringement of a registered mark (15 U.S.C. § 1114) or an unregistered mark (15 U.S.C. § 1125(a)) must prove that it owns a valid, protectable mark and that the defendant's use of a similar mark in connection with goods or services creates a "likelihood of confusion."

Likelihood of confusion requires proof that confusion is probable, not proof that consumers were in fact confused. A plaintiff who can show that the defendant's mark, in the context of the defendant's goods, services, and marketing, would cause an appreciable number of reasonably prudent purchasers to be mistaken about who made, sponsored, or is affiliated with the defendant's products has proven infringement.

The Fifth Circuit's Digits of Confusion

Each federal circuit applies its own multi-factor test for likelihood of confusion. In the Fifth Circuit (which includes Texas), courts evaluate eight factors, known as the "digits of confusion."

Strength of the plaintiff's mark. Stronger marks receive broader protection. Strength has two dimensions: inherent distinctiveness (where the mark falls on the spectrum from generic to fanciful) and commercial strength (the recognition the mark has acquired in the marketplace through advertising, sales volume, length of use, and consumer awareness). An arbitrary or fanciful mark that's been used for decades with substantial advertising enjoys the broadest protection. A descriptive mark with limited commercial recognition receives the narrowest.

Similarity of the marks. Courts compare the marks' visual appearance, sound (phonetics), and meaning (connotation) as they would be encountered by consumers in the marketplace, not in isolation or through side-by-side dissection. Similarity is assessed based on the overall commercial impression each mark conveys. Marks that look different on paper may sound alike when spoken (BRIZZY vs VIZZY, though the courts in that dispute ultimately found confusion unlikely), and marks that look and sound different may convey the same meaning.

Similarity of the products or services. If the plaintiff and defendant sell identical or closely related goods, confusion is more likely. If they operate in entirely different industries with no overlap, confusion is less likely. Courts also consider whether consumers would expect the plaintiff to expand into the defendant's market.

Identity of retail outlets and purchasers. If both products are sold through the same channels (the same retail stores, the same online platforms, the same industry trade shows) to the same customers, confusion is more likely. If the products reach different markets through different channels, the risk diminishes.

Similarity of advertising media. If both parties advertise through the same media (the same trade publications, the same social media platforms, the same geographic market), consumers are more likely to encounter both marks and be confused.

Defendant's intent. A defendant who adopted the mark with the intent to derive benefit from the plaintiff's reputation is more likely to have created confusion. "Mere awareness" of the plaintiff's mark when choosing the defendant's mark doesn't establish bad intent. Courts look for evidence that the defendant intended to trade on the plaintiff's goodwill, such as imitating packaging, adopting similar distribution methods, or targeting the same customer base.

Actual confusion. Evidence that consumers have in fact been confused (misdirected phone calls, emails intended for one company sent to the other, customer testimony, consumer surveys) is persuasive but not required. Actual confusion is one factor in the analysis rather than an element of the claim. Absence of actual confusion evidence doesn't defeat the claim, particularly when the defendant's product is new and hasn't been on the market long enough for confusion to manifest.

Degree of care exercised by purchasers. Sophisticated purchasers who conduct research before buying (industrial equipment buyers, enterprise software customers) are less likely to be confused than impulse purchasers of inexpensive consumer goods (grocery shoppers scanning a shelf). When purchasers exercise a high degree of care, a greater degree of similarity is required to establish confusion.

No single factor is dispositive. Courts weigh each factor based on the facts of the case, and a finding of likelihood of confusion doesn't require a positive finding on a majority of the factors. The Fifth Circuit places particular weight on two digits. Bad intent alone can justify an inference of confusion, and actual confusion is the best evidence of it.

Registered Versus Unregistered Marks

Federal registration provides the plaintiff procedural and evidentiary advantages in a § 1114 infringement suit. Under 15 U.S.C. § 1115(a), the registration certificate is prima facie evidence of validity, the registrant's ownership, and the registrant's exclusive right to use the mark in commerce for the listed goods or services. An infringement claim based on an unregistered mark proceeds under § 1125(a) (false designation of origin), which provides the same substantive remedies but requires the plaintiff to prove the mark's validity and protectability without the benefit of the registration presumption.

Counterfeiting

Counterfeiting is the "hard core" of trademark infringement. A counterfeit mark is a spurious mark that's identical to, or substantially indistinguishable from, a registered mark. Counterfeiting requires proof that the defendant intentionally used the counterfeit mark knowing it was counterfeit, and that the use created a likelihood of confusion.

Counterfeiting triggers enhanced remedies under § 1117: treble damages (or, at the plaintiff's election, statutory damages of up to $200,000 per counterfeit mark per type of goods or services, or up to $2,000,000 if the counterfeiting was willful), court-ordered destruction of the counterfeit goods and materials (§ 1118, at the court's discretion), and ex parte seizure orders allowing the plaintiff to seize counterfeit goods without prior notice to the defendant (§ 1116(d)).

Remedies for Trademark Infringement

Injunctive relief. Under § 1116 (15 U.S.C. § 1116), courts may grant injunctions to prevent further infringement. A permanent injunction after trial follows the four-factor equitable test of eBay Inc. v. MercExchange, LLC, 547 U.S. 388 (2006). Preliminary injunctions during the case follow the traditional preliminary injunction factors, and under § 1116(a) a trademark plaintiff who shows likelihood of success receives a rebuttable presumption of irreparable harm.

Monetary remedies. Under § 1117(a) (15 U.S.C. § 1117(a)), a prevailing plaintiff can recover the defendant's profits attributable to the infringement, the plaintiff's damages sustained as a result of the infringement, and costs of the action. In assessing profits, the plaintiff is required only to prove the defendant's gross revenue from the infringing sales; the defendant bears the burden of proving deductions for costs and expenses. Recovery reaches only the named defendant's own profits, not a non-party affiliate's, absent veil-piercing. Dewberry Group, Inc. v. Dewberry Engineers Inc., 604 U.S. 321 (2025). The court may increase a damages award up to three times the amount found. A profits award the court finds inadequate or excessive can be adjusted to whatever sum the court finds just, and any award must be compensation, not a penalty. Romag Fasteners, Inc. v. Fossil Group, Inc., 590 U.S. 212 (2020), held that willfulness isn't a prerequisite for an award of the infringer's profits under § 1117(a), though it remains a relevant consideration.

Attorney's fees. Under § 1117(a), "the court in exceptional cases may award reasonable attorney fees to the prevailing party." Under the Octane Fitness standard (adopted for trademark cases from patent law), an "exceptional case" is one that stands out from others based on the totality of the circumstances, including the objective unreasonableness of the losing party's position or the unreasonable manner in which the case was litigated.

Defenses

Fair use (descriptive fair use) allows the defendant to use a term that happens to be the plaintiff's trademark in its descriptive sense (not as a trademark) to describe the defendant's own goods. A defendant who uses the word "sharp" to describe the edge of a knife isn't infringing the SHARP trademark for electronics.

Nominative fair use allows the defendant to use the plaintiff's mark to refer to the plaintiff's own goods (in comparative advertising, reviews, or resale of genuine goods) without creating confusion about sponsorship or endorsement.

Laches bars a trademark infringement claim if the plaintiff unreasonably delayed in asserting its rights and the defendant was prejudiced by the delay.

Practical Recommendations

Register your marks federally before infringement occurs. Registration creates the presumption of validity and ownership, which simplifies the infringement case. Without registration, the plaintiff must prove the mark's validity, protectability, and the geographic scope of its rights through extrinsic evidence.

Document consumer confusion when it happens. Misdirected calls, emails, social media messages, and customer complaints about the "wrong" product are powerful evidence of actual confusion. Create a system for capturing and preserving these instances.

Evaluate the defendant's intent through publicly available evidence before filing suit. How did the defendant select its mark? Did the defendant conduct a trademark search? Did the defendant know about the plaintiff's mark? Intent evidence strengthens the case and increases the likelihood of enhanced remedies.

If your business receives a cease-and-desist alleging trademark infringement, don't ignore it. Continued use of the mark after receiving notice of the plaintiff's rights strengthens the plaintiff's argument for willfulness, which increases the risk of enhanced damages, counterfeiting claims, and an exceptional case finding for attorney's fees. Evaluate the claim on the merits, consult an attorney, and make an informed decision about whether to rebrand, negotiate coexistence, or defend.