The 5 Most Contested Trademark Classes: Data From 204K TTAB Oppositions

Class 5 (Pharmaceuticals) ranks sixth by opposition volume. But it has the highest opposition rate of any major trademark class at 3.8%, meaning 1 in every 25 filings gets challenged. That makes it more contested than Class 9 (software), Class 35 (business services), or any of the classes that dominate the opposition leaderboard by raw count.

That single number reframes how you think about trademark risk. Volume tells you where the most disputes happen. Rate tells you where your filing is most likely to become one.

This report examines 204,486 distinct opposition proceedings from the Trademark Trial and Appeal Board (TTAB), the USPTO body that adjudicates disputes over pending trademark applications. An opposition is a formal challenge filed during the 30-day window after a trademark is approved for publication, arguing that the mark should not register. They are expensive (legal costs typically run $15,000 to $50,000+), slow (median resolution takes 2.4 to 2.6 years), and overwhelmingly unsuccessful for challengers, who win just 1.2% of all proceedings.

Yet approximately 18,000 to 20,000 new oppositions are filed every year, a small but significant fraction of the 600,000+ annual trademark applications at the USPTO.

For readers unfamiliar with the classification system: the Nice Classification is the international standard for categorizing goods and services into 45 classes. Class 9 covers software and electronics. Class 25 covers clothing. Every trademark application specifies one or more classes, and this categorization determines which existing marks yours will be compared against. The class you file in shapes your opposition risk, the duration of any proceeding, and even how likely a challenger is to succeed.

Methodology

This analysis covers 204,486 distinct TTAB opposition proceedings from Signa's production database, spanning all available historical records through 2025. Year-over-year trends focus on 2016 to 2025 for consistency.

Because a single opposition can involve trademarks covering multiple Nice classes, one proceeding may appear in the counts for several classes. The class-level numbers reflect how many oppositions touched each class, not unique proceedings. This approach captures opposition exposure per class, which is the relevant metric for filers deciding where to register.

Four metrics structure the analysis. Opposition volume is the raw count of proceedings per class. Opposition rate is oppositions divided by total filings in that class, showing the probability any given filing faces a challenge. Challenger success rate is the percentage of decided cases (wins plus losses only, excluding withdrawals, settlements, pending, and other outcomes) where the challenger prevailed. Duration is the time from filing to resolution, reported as both median and average.

Two of these metrics deserve a note on denominators. The outcome tables later in this report show each outcome category as a percentage of all proceedings, including withdrawn and pending cases. The challenger success rate uses a narrower denominator: only cases where the TTAB issued a decision. A challenger win rate of 0.8% of all proceedings in Class 9 translates to 2.0% of decided cases, because most proceedings never reach a decision.

The Top 5 Most Contested Classes by Volume

By raw count, five classes account for a disproportionate share of all TTAB oppositions.

Class 9 leads with nearly 58,000 oppositions, 4.5% more than Class 35 (55,443). But look at the rates: Class 35 filings are challenged at 3.7% versus 3.0% for Class 9. More oppositions happen in Class 9 because more filings happen in Class 9 (1.9 million), not because the per-filing risk is higher.

The drop-off after the top 5 is notable. Class 5 (Pharmaceuticals), ranked sixth, has 23,679 oppositions, an 8% drop from Class 25's count. Each of the top 5 classes exceeds 25,000 oppositions; no class outside the top 5 reaches 24,000.

But volume alone does not capture where opposition risk is highest. For that, look at the Nice class opposition rates, which tell a different story entirely.

Class 9: Software and Electronics

57,927 oppositions from 1.9 million filings. 3.0% opposition rate. Median duration: 945 days.

Class 9 generates more opposition proceedings than any other Nice class. The reason is structural: software product naming conventions produce collisions at scale. Short, invented words. Compound terms combining common English words with tech suffixes. Acronyms. The naming patterns that work well for software branding also produce marks that overlap phonetically or conceptually with existing registrations.

The DuPont factors, the 13 criteria the TTAB uses to assess likelihood of confusion, weigh heavily on similarity of marks and similarity of goods. In Class 9, the "similarity of goods" factor is almost always present because the class covers an enormous range of products: downloadable software, mobile apps, computer hardware, electronic sensors, headphones. Two marks in Class 9 are automatically closer in scope than marks across different classes.

From 2016 to 2025, Class 9 oppositions grew 34%, from 4,179 per year to 5,623. That growth roughly tracks the rise in filing volume across the same period (59,123 filings in 2016 to 80,607 in 2025), which means the opposition rate stayed relatively stable. The problem is not getting worse per filing. There are simply more filings, and each one carries the same baseline risk.

Challengers succeed in 2.0% of decided cases in Class 9. Class 9's median resolution time of 945 days (2.6 years) is the longest of any top-5 class, averaging 1,096 days (3.0 years) when outliers pull the mean up. For a software company, that means an opposition filed at launch might not resolve until your product is in its third major version.

One notable pattern: 44% of Class 9 oppositions end in withdrawal. That is higher than Class 25 (33%) but lower than Class 42 (47%). Withdrawals can mean several things (the applicant abandoned the mark, parties reached a private agreement, or the challenger reconsidered), but the high withdrawal rate in tech classes suggests many oppositions function as a negotiating tool rather than a path to a TTAB decision.

Class 35: Business Services

55,443 oppositions from 1.5 million filings. 3.7% opposition rate. Median duration: 875 days.

Class 35 covers advertising, business management, office functions, and retail services. It is the catch-all class for service-based businesses, and that breadth is precisely what makes it contentious. Marks in this class frequently describe what the business does, pushing them toward the boundary between protectable and merely descriptive.

The 3.7% opposition rate (second only to Class 5's 3.8%) reflects this tension. Descriptiveness challenges are among the most common grounds for opposition, and Class 35 marks invite them. A name like "SmartBooks" for accounting services, "QuickShip" for logistics management, or "FreshMeal" for restaurant services straddles the line between a distinctive brand name and a description of the service itself. Competitors see these marks as attempts to claim ownership over common language.

Despite the high opposition rate, Class 35 has the fastest median resolution at 875 days, roughly 70 days shorter than Class 9. Average resolution sits at 992 days. The relatively faster resolution may reflect the nature of descriptiveness disputes: they tend to turn on clearer legal standards than confusion-based oppositions, giving the TTAB a more straightforward path to decision.

Challenger success rate in decided cases is 2.0%. Growth from 2016 to 2025 was 33.5% (4,039 to 5,393 per year), nearly identical to Class 9's trajectory. The two classes move in lockstep, each reflecting the broader growth in service-economy trademark filings.

Class 42: SaaS and Computer Services

39,613 oppositions from 1.2 million filings. 3.2% opposition rate. Median duration: 925 days.

Class 42 is the growth story in this dataset.

From 2016 to 2025, oppositions in Class 42 grew 71%, from 2,411 per year to 4,116. No other top-5 class comes close to that rate of increase. Class 41 grew 39%. Class 9 grew 34%. Class 25 grew 19%. Class 42 nearly doubled its annual opposition count in under a decade.

The driver is the SaaS explosion. Class 42 covers "design and development of computer hardware and software" and "software as a service" (SaaS). As cloud software proliferated in the late 2010s and early 2020s, filings surged, and opposition activity followed. The growth peaked in 2022 at 4,411 oppositions before settling to 4,116 in 2025, suggesting the market may be reaching a new equilibrium.

The 3.2% opposition rate sits between Class 9 (3.0%) and Class 35 (3.7%). Challenger success rate is slightly higher at 2.4% of decided cases, possibly because SaaS naming conventions produce tighter overlap: many SaaS products combine a common word with a suffix like "-ly," "-ify," or "-io," creating clusters of similar-sounding marks.

Class 42 also has the highest withdrawal rate of any top-5 class at 47%, meaning nearly half of all oppositions end without a decision. In the SaaS world, where companies pivot, rebrand, or shut down frequently, withdrawals may partly reflect applicants abandoning marks as their products change direction. For challengers, this means that filing an opposition in Class 42 has a reasonable chance of clearing the mark without a TTAB fight, simply because the applicant may move on.

Class 41: Education and Entertainment

30,341 oppositions from 1.4 million filings. 2.2% opposition rate. Median duration: 880 days.

Class 41 has the lowest opposition rate of the top 5 at 2.2%, but it tells a different story in the outcome data. Challengers succeed in 3.3% of decided cases, the second-highest rate among the top 5 classes. When oppositions do happen in Class 41, challengers are meaningfully more likely to prevail.

The class covers education, training, entertainment, sporting activities, and cultural events. The content and streaming boom drove a 39% increase in oppositions from 2016 to 2025 (2,145 to 2,975 per year), as media companies, streaming platforms, educational technology startups, and gaming publishers all competed for brand territory.

What makes Class 41 different from the tech-heavy classes (9 and 42) is the nature of the marks. Entertainment and media brands tend to be more distinctive (think event names, show titles, game names), which means fewer filings cross the confusion threshold. But when they do cross it, the overlap tends to be more clear-cut, giving challengers a stronger case.

The median resolution of 880 days and average of 986 days place Class 41 in the middle of the pack. Withdrawal rates are moderate at 43%, and the settled rate (0.5%) is the lowest of any top-5 class, suggesting fewer private deals are reached compared to the tech classes.

Class 25: Clothing

25,746 oppositions from 1.3 million filings. 2.0% opposition rate. Median duration: 881 days.

Class 25 has the lowest opposition rate in the top 5 (2.0%), the slowest growth (19% from 2016 to 2025), and the fewest total oppositions. By those measures, it is the least contested of the group. But it is the most dangerous class for applicants who do face an opposition.

Challengers win 4.1% of decided cases in Class 25, more than double the rate in Class 9 or Class 35 (both 2.0%). That makes Class 25 the class where challengers are most likely to succeed.

Two patterns explain this. First, Class 25 has the lowest withdrawal rate of any top-5 class at 33%, compared to 44% in Class 9 and 47% in Class 42. When a challenger files an opposition in Class 25, they are less likely to walk away. Fashion and apparel disputes tend to involve established brands with dedicated legal budgets defending marks they consider core to their identity.

Second, the nature of clothing brands creates clearer confusion cases. Clothing marks are often short, stylized words or names. Two similar-sounding clothing brands selling to the same consumer demographic present a straightforward confusion argument. The TTAB does not need to parse whether software products are functionally similar (a nuanced question in Class 9). Two clothing lines selling t-shirts and jeans are obviously in the same market.

Growth at 19% (1,939 to 2,308 per year) is the slowest of any top-5 class. The clothing trademark market is mature relative to the tech classes. Filing volumes are not exploding the way SaaS filings are, so opposition counts are not accelerating either. But the high challenger success rate means that for any individual applicant facing an opposition in Class 25, the risk is real.

The Surprise: Class 5 Pharmaceuticals

Class 5 ranks sixth by opposition volume with 23,679 proceedings. But it has the highest opposition rate of any major class at 3.8%, calculated from just 628,629 total filings. That is less than half the filing volume of Class 25 and a third of Class 9's volume.

The rate is not a statistical artifact of a small sample. With 628,000+ filings and nearly 24,000 oppositions, the data is robust. One in every 25 pharmaceutical trademark filings faces a formal challenge.

Pharmaceutical naming is uniquely constrained. Drug names must be distinct not just from other trademarks but from other drug names, because confusion between medications creates patient safety risks. The FDA reviews proposed drug names for potential confusion before they reach the market, and the same concerns motivate trademark oppositions. A pharmaceutical company that allows a confusingly similar mark to register faces regulatory scrutiny in addition to the standard brand confusion issues.

This creates an environment where companies challenge marks proactively. The cost of an opposition ($15,000 to $50,000+) is negligible compared to the cost of a medication error caused by name confusion, or the regulatory consequences of allowing confusing marks to coexist. Where tech companies might tolerate a somewhat similar mark in an adjacent product category, pharmaceutical companies challenge aggressively.

For founders in health tech, supplements, or any product touching Class 5: the data shows your filing has nearly double the opposition risk of a software filing in Class 9 (3.8% vs. 3.0%). Thorough clearance searching before filing is not optional in this class.

How Long Does a Trademark Opposition Take?

The short answer: plan for two and a half years.

Across all five classes, medians range from 875 to 945 days. The gap between median and average is telling: averages run 106 to 151 days longer because a tail of complex, multi-year cases pulls the mean upward. The median is the better planning number, but even a median of 875 days means you should not expect resolution before two full years.

Class 9 is the slowest at both median (945 days) and average (1,096 days). The complexity of software-related confusion analysis likely contributes: determining whether two software products are similar in function requires technical evaluation that clothing or business service comparisons do not.

For product planning, these timelines mean that an opposition filed against your trademark on the day you launch will, on average, resolve around the time you are shipping version 3.0. If your brand strategy depends on the registered mark (for domain disputes, marketplace enforcement, or international filings via the Madrid Protocol), an opposition creates years of uncertainty.

Consult a trademark attorney for guidance on managing business operations during a pending opposition.

What the Outcomes Tell Us

The overall outcome distribution across 204,486 proceedings (percentages are of all proceedings, not just decided cases):

Challengers win 1.2% of all proceedings. Narrow the denominator to only decided cases (where the TTAB ruled for one side), and the rate rises to 2.4%. Both numbers are striking, especially given the cost and duration involved. Nearly half of all oppositions (49.2%) end with the challenger losing outright, and another 35% are withdrawn.

But the withdrawal category complicates the picture. A withdrawal can mean the challenger gave up. It can also mean the applicant voluntarily abandoned the mark, which from the challenger's perspective is a win without a formal decision. The data does not distinguish between these scenarios. In Class 42, where 47% of oppositions are withdrawn, a significant portion likely reflects applicants who moved on, effectively giving challengers the outcome they wanted. The real deterrent effect of oppositions is larger than any win-rate metric captures.

The per-class breakdown reveals where the dynamics differ. Percentages in this table are of all proceedings in each class. The final column shows the challenger success rate among decided cases only (wins divided by wins plus losses), the standard metric for evaluating how likely a challenger is to prevail when the TTAB rules.

Class 25 stands out again. It has the highest raw count of challenger wins (537) despite having the fewest total oppositions in the top 5. Its withdrawal rate (33%) is far below the average, confirming that fashion disputes are fought to conclusion more often than tech disputes. When a luxury brand or major retailer files an opposition in Class 25, they are not bluffing.

Class 42's 47% withdrawal rate, the highest in the group, reinforces the SaaS dynamics discussed earlier: rapid company turnover means many applicants disappear before the opposition resolves.

Implications for Filers

The data points toward four practical conclusions.

Know your class-level risk. Opposition rates vary nearly 2x across the top classes (2.0% in Class 25 to 3.8% in Class 5). If you are filing in a high-rate class, your clearance search needs to be proportionally thorough. A surface-level search that might suffice in a lower-risk class could leave you exposed in Class 5 or Class 35.

In Class 25, take oppositions seriously. A 4.1% challenger success rate (of decided cases), double the rate in tech classes, means challengers in fashion and apparel are more likely to win and more likely to fight to the end. If an established clothing brand opposes your mark, the historical data suggests they are not filing as a negotiating tactic.

Watch Class 42. With 71% growth in opposition activity over the past decade, Class 42 is on a trajectory that could see it overtake Class 35 within the next five to seven years. SaaS companies filing in Class 42 today face a more crowded opposition environment than even two or three years ago.

Budget for duration. Regardless of class, plan for a minimum of two years if an opposition is filed. Average durations exceed 2.7 years in every top-5 class, and Class 9 averages 3.0 years. Build your brand launch and IP strategy to function during a pending proceeding.

Consult a trademark attorney for legal guidance specific to your filing strategy and risk tolerance.

Full Methodology

Data source. All opposition data was pulled from Signa's production database, which indexes TTAB proceedings from the USPTO. Filing volume data covers total trademark applications across the same classes for opposition rate calculations.

Scope. 204,486 distinct TTAB opposition proceedings across all 45 Nice classes, with detailed analysis of the top 5 by volume and Class 5 (pharmaceuticals) as a notable outlier.

Multi-class counting. A single opposition may involve marks filed in multiple Nice classes. Each class associated with a proceeding is counted separately. This means the sum of class-level opposition counts exceeds the total number of distinct proceedings. This is intentional: the goal is to measure opposition exposure per class, not to count unique proceedings.

Definitions. "Challenger success rate" is calculated as challenger wins divided by total decided cases (wins plus losses), excluding withdrawn, settled, pending, and other outcomes. "Opposition rate" is total oppositions in a class divided by total filings in that class. Duration is calculated only for proceedings with a recorded resolution date.

Limitations. Withdrawal ambiguity is the primary limitation. Withdrawn proceedings may represent challenger abandonment, applicant abandonment, or private resolution, and the data does not distinguish between these. The "other" category (6.7% of outcomes) includes procedural dispositions that do not fit standard categories. Pending cases (6.3%) are excluded from outcome and duration analysis.

Signa's API provides access to opposition proceeding data across 200+ trademark offices. Explore trademark opposition statistics and filing trends at api.signa.so.