The Largest B2B SEO Agencies in the US — 2024

While being the largest agency is no indication of being the best, the size of a B2B SEO agency implies a track record of success. It also correlates with economies of scale, in which specialists in multiple facets of B2B SEO are likely to be on staff to support the breadth of the agency’s client base; thus, if you have a conversion optimization or UX design need, for example, there will be an expert available. 

The table below lists the top 8 largest B2B SEO agencies in the US, with the criteria being that the firm has greater than $10M in revenue and/or 100 employees—both of which are levels that demonstrate an established professional services business with a quality product. We also consider each firm’s notable clients, web citations, and reputation in their respective niches.

The Largest B2B SEO Agencies In The US – 2024

# Name  Headquarters Year Founded Notable Clients Specialties
1 First Page Sage San Francisco, CA 2009 Salesforce, Logitech, US Bank Thought Leadership-based SEO
2 Duffy Agency  Dover, NH 2009 Cavidi, the UN World Food Programme International & Multilingual SEO
3 Marketing Eye Atlanta, GA 2004 Safeway, Denticare, Cirrus Networks Technical SEO & Web Design
4 Clay Agency San Francisco, CA 2016 Slack, Coinbase, UPS Conversion Rate and UX Optimization for SEO
5 Epsilon Irving, TX 1969 Walgreens, Coach, Volvo Full-Service Enterprise Marketing
6 Community Boost San Diego, CA 2012 The Trevor Project, The Humane Society, Seniors At Home. SEO for Nonprofits
7 AMP Agency New York, NY 1995 Microsoft, Vizio, Asus Video SEO
8 Metric Theory San Francisco, CA 2012 GoFundMe, Lyft, LexisNexis SEO & Paid Search

The Largest B2B SEO Agencies in the US, Summarized

For Thought Leadership & SEO – First Page Sage 

First Page Sage is the largest SEO agency in the US. The firm’s approach centers on creating thought leadership content that generates marketing qualified leads.

First Page Sage’s campaign process begins with a content team interviewing subject matter experts, studying the client’s market, and publishing several pages of new content on a weekly basis. Most of First Page Sage’s clients consist of companies in technical B2B industries such as SaaS, IT, and manufacturing. Notable clients include Salesforce, Logitech, and US Bank.

  • Year Founded: 2009
  • Headquarters: San Francisco, CA
  • Services: Thought Leadership-based SEO, SEO Strategy Consulting, Conversion Optimization
Summary of Online Reviews
First Page Sage uses “an in-depth onboarding period” in order to create “excellent content” to support their heavy focus on ROI and lead generation”, but some customers find that they are slower to produce results than firms with a greater focus on paid marketing.

For International SEO – Duffy Agency 

The Duffy Agency specializes in international and multilingual SEO. They specialize in working with aspiring international brands to develop marketing strategies that target markets in multiple countries and languages.

SEO requires developing a working knowledge of the technical jargon and language that signals expertise to buyers, and international SEO is no different. The Duffy Agency works with their clients to translate nuanced industry knowledge into various languages to make content tailored for each target market. Their clients have included Cavidi and the UN World Food Programme.

  • Year Founded: 2009
  • Headquarters: Dover, NH
  • Services: International SEO, Multilingual SEO
Summary of Online Reviews
Duffy Agency targets “ambitious” goals for their services but often succeed “without increasing campaign cost“. While their results must “build over time“, they are “dramatic“.

For Technical SEO – Marketing Eye 

Marketing Eye is a creative marketing services firm based out of Atlanta, GA, that focuses on the technical and web design aspects of SEO.

Unlike other marketing agencies that offer total content production, Marketing Eye looks to optimize existing content for keyword relevancy and search intent. This makes them a good fit for companies that already have strong in-house content teams but lack SEO or technical expertise, and their clients have included Safeway, Cirrus Networks, and Denticare.

  • Year Founded: 2004
  • Headquarters: Atlanta, GA
  • Services: Marketing Automation, Marketing Consulting, Web Development
Summary of Online Reviews
Marketing Eye’s team are both “competent and professional” despite sometimes needing “additional training.” Nevertheless, their service is “superior“.

For UX and Conversion Optimization – Clay Agency

Clay Agency was founded in 2016, and they’re the youngest agency on this list. They place their focus squarely on the difficult process of conversion rate and UX optimization, and increasing conversion rates of organic visitors.

SEO requires conversion optimization to be effective: organic traffic is only as valuable when it converts into actual sales leads. Clay Agency is a good fit for companies that have strong organic traffic numbers but struggle with their conversion rates. Their clients have included Slack, Coinbase, and UPS.

  • Year Founded: 2016
  • Headquarters: San Francisco, CA
  • Services: UI/UX design, Product & Brand Strategy, Conversion Rate Optimization.
Summary of Online Reviews
Clay Agency’s design focus is “high-quality and they deliver their services at a “great price“. Their teams pay “close attention to detail” for branding focused clients.

For Enterprises – Epsilon

Epsilon is a full-service enterprise marketing company that combines traditional and digital marketing into a single campaign. They specialize in working with enterprise companies, and the strategic demands unique to enterprise SEO.

Because enterprises often have complex vendor vetting and setup processes, they often need a single agency to handle all of their marketing needs. Epsilon is capable of uniting disparate marketing channels under one roof, and their past clients include Walgreens, Coach, and Volvo.

  • Year Founded: 1969
  • Headquarters: Irving, TX
  • Services: Digital Media, Data Solutions, Customer Insights
Summary of Online Reviews
Epsilon’s teams are “attentive” and “responsive” to enterprise clients needs, and customers report that their “very costly” pricing is made up for by strong results.

For Nonprofits – Community Boost

The San Diego-based Community Boost offers a full suite of digital marketing services for nonprofits and charitable organizations, with SEO as one of their core services. The inherent trust that visitors confer on websites appearing in organic search results is particularly important for nonprofits, particularly when seeking donations from high net worth individuals and corporate sponsors.

Agencies that specialize in this niche—and are therefore familiar with the tone and SEO strategies most effective for nonprofits to use—are relatively rare. Community Boost is the largest agency among them, and their past clients include The Trevor Project, The Humane Society, and Seniors At Home.

  • Year Founded: 2012
  • Headquarters: San Diego, CA
  • Services: SEO for Nonprofits, Youtube & Display Ad Management, Google Ad Grant Management
Summary of Online Reviews
While teams are “dedicated to their craft” and Community Boost is an “incredible partner” for nonprofits, their processes still have “small tweaks to iron out” despite their relatively long tenure.

For Video SEO – AMP Agency

AMP Agency is a full-service digital marketing agency, with video SEO being a major focus. They help companies optimize video titles and descriptions to drive views and engagement, optimizing for YouTube’s unique algorithm.

AMP is a good fit for companies that attract customers primarily through their video content. Their clients have included Microsoft, Vizio, and Asus.

  • Year Founded: 1995
  • Headquarters: Boston, MA
  • Services: Video SEO, Integrated Media Strategy, Digital Experience Design & Development
Summary of Online Reviews
AMP Agency creates “collaborative” relationships with their clients, providing teams that are “efficient, straightforward, and persistent“, but sometimes “small things get missed“.

For SEO & Paid Search – Metric Theory

Metric Theory was founded in 2012 and focuses on combining SEO with paid search and remarketing. By tracking your visitors, they can help you optimize your ad spend by displaying ads only to prospects who have found your website organically.

Despite its high ROI, SEO’s relatively long time frame before results are seen can be off putting for many marketing teams. Paid advertising is a useful way to bridge this gap, lowering the overall average ROI of marketing efforts for increased short term lead generation. Metric Theory is a good fit for companies who need short-term lead generation over long-term ROI, and their clients have included GoFundMe, Lyft, and LexisNexis.

  • Year Founded: 2012
  • Headquarters: San Francisco, CA
  • Services: SEO, Paid Search, Remarketing & Display Ads
Summary of Online Reviews
Metric Theory conducts “thorough background research” and are “effective at capitalizing on revenue sources“, but teams would “benefit from having more resources“.

The Top B2B SEO Agencies in the US, by Industry

Our team has researched the top SEO agencies for each of the following industries:

The full reports may be found in the links above, and the top 5 agencies for each industry, as well as their industry reputation score, are listed below:

The Top SaaS SEO Agencies

Rank Agency Industry Reputation Score
1 REQ 4.9
2 First Page Sage 4.9
3 Clay Agency 4.7
4 Epsilon 4.5
5 Marketing Eye 4.4

The Top Manufacturing SEO Agencies

Rank Agency Industry Reputation Score
1 Kula Partners 4.8
2 First Page Sage 4.8
3 Industrial Strength Marketing 4.6
4 Windmill Strategy 4.5
5 Factory Web Source 4.4

The Top Real Estate SEO Agencies

Rank Agency Industry Reputation Score
1 REQ 5.0
2 First Page Sage 5.0
3 Portal Ventures 4.8
4 ReachLocal 4.7
5 Jives Media  4.6

The Top Healthcare SEO Agencies

Rank Agency Industry Reputation Score
1 RNO1 4.9
2 First Page Sage 4.9
3 k2md Health 4.7
4 REQ 4.6
5 iHealthSpot 4.4

The Top Fintech & Financial Services SEO Agencies

Rank Agency Industry Reputation Score
1 First Page Sage 5.0
2 Yes& Agency 4.9
3 TOP Agency 4.8
4 CSTMR 4.5
5 Banktastic 4.5
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