Core Web Vitals have become the defining factor separating high-performing websites from those losing revenue to poor user experience. According to the 2024 HTTP Archive Web Almanac, only 48% of mobile websites and 54% of desktop websites passed ALL Core Web Vitals metrics in 2025, creating massive opportunities for businesses that partner with the right technical SEO agencies.
The stakes couldn’t be higher for growth-stage SaaS, B2B services, and e-commerce companies. When Rakuten 24 optimized their Core Web Vitals, they achieved a 33.13% lift in conversion rate—demonstrating the tangible business impact of expert technical SEO work. Similarly, leading agencies are delivering an average 508% ROI for their clients through strategic Core Web Vitals optimization.
This comprehensive analysis evaluates 15 top technical SEO agencies based on their Core Web Vitals expertise, proven results, pricing transparency, and ability to drive meaningful business outcomes for growth-focused companies. Ready to transform your website performance? Get Your Custom Growth Strategy to explore your options.
Why Core Web Vitals Are Critical for Business Growth in 2025
Core Web Vitals measure three essential user experience factors: Largest Contentful Paint (LCP) for loading performance, First Input Delay (FID) for interactivity, and Cumulative Layout Shift (CLS) for visual stability. These metrics directly impact both search rankings and conversion rates, making them business-critical for companies seeking sustainable growth.
“The gap between high-performing and underperforming websites continues to widen. Companies that invest in proper Core Web Vitals optimization see immediate improvements in user engagement, search visibility, and revenue generation.” – Industry Technical SEO Expert
Consider Swappie’s transformation: their mobile site suffered from poor Core Web Vitals performance until they partnered with a dedicated technical SEO team. The results were remarkable. LCP improved by 55%, CLS improved by 91%, and mobile revenue jumped 42%. This demonstrates why selecting the right agency partner is crucial for meaningful business impact.
How We Evaluated the Top Agencies
Our analysis evaluated agencies across five critical criteria specifically relevant to Core Web Vitals optimization:
- Technical Expertise: Depth of Core Web Vitals knowledge, proprietary tools, and advanced optimization techniques
- Proven Results: Documented case studies with specific performance improvements and business outcomes
- Industry Specialization: Experience with SaaS, B2B services, and e-commerce platforms
- Service Comprehensiveness: Integration of technical SEO with broader growth strategies
- Client Success Stories: Verified testimonials and long-term partnership success
This methodology ensures our rankings reflect real-world value for growth-stage businesses seeking transformative performance improvements rather than incremental changes.
The 15 Best Technical SEO Agencies for Core Web Vitals
1. Single Grain – Best Overall Choice for Growth-Stage Companies ⭐
Single Grain stands out as the premier choice for businesses seeking comprehensive technical SEO expertise integrated with data-driven growth strategies. Their approach combines deep technical knowledge with creative storytelling and conversion optimization, making them uniquely positioned to deliver both performance improvements and business results.
Core Web Vitals Expertise: Single Grain’s technical team specializes in complex Core Web Vitals optimization for SaaS platforms, e-commerce sites, and B2B services. They’ve developed proprietary methodologies that address the specific challenges facing growth-stage companies, including JavaScript-heavy applications and dynamic content systems.
Proven Results: Single Grain has demonstrated consistent success in improving Core Web Vitals while driving measurable business outcomes. Their integrated approach ensures technical improvements translate directly into increased conversions and revenue growth.
Industry Focus: Specialized expertise in SaaS, fintech, crypto, and e-commerce sectors with deep understanding of growth-stage company challenges and opportunities.
Service Integration: Unlike agencies that focus solely on technical fixes, Single Grain integrates Core Web Vitals optimization with content strategy, conversion rate optimization, and comprehensive growth planning.
Discover how Single Grain can accelerate your growth. Get Your Custom Growth Strategy to discuss your specific needs.
2. WebFX – Best for Enterprise-Scale Operations
WebFX brings enterprise-level capabilities to Core Web Vitals optimization through their proprietary MarketingCloudFX platform. Their strength lies in managing large-scale technical SEO projects with comprehensive monitoring and reporting capabilities.
Strengths: Proprietary technology stack, scalable optimization processes, Fortune 500 experience
Best For: Large enterprises with complex technical infrastructures
Limitations: May be overkill for smaller growth-stage companies
3. Siege Media – Best for Content-Integrated Technical SEO
Siege Media excels at combining Core Web Vitals optimization with content strategy, making them ideal for businesses that rely heavily on content marketing for growth.
Strengths: Content-technical integration, e-commerce expertise, proven track record with national retailers
Best For: Content-heavy e-commerce sites and brands with extensive product catalogs
Limitations: Less specialized in pure SaaS technical challenges
4. Onely – Best for JavaScript-Heavy Applications
Onely has built a reputation as the go-to agency for complex JavaScript SEO and Core Web Vitals optimization, particularly for React and Angular applications.
Strengths: JavaScript SEO expertise, technical depth, experience with complex architectures
Best For: SaaS companies with JavaScript-heavy platforms
Limitations: More focused on technical execution than strategic business growth
5. NinjaPromo – Best for SaaS and Fintech
NinjaPromo specializes in technical SEO for high-growth SaaS and fintech companies, with particular expertise in Core Web Vitals optimization for complex dashboards and user interfaces.
Strengths: SaaS specialization, fintech experience, tailored optimization approaches
Best For: B2B SaaS platforms and fintech applications
6. SALT.agency – Best for International Enterprise
SALT.agency brings deep technical expertise to global enterprise clients, with proven results in Core Web Vitals optimization for large-scale international websites.
Strengths: International SEO expertise, enterprise experience, documented case studies
Best For: Global enterprises with multi-market presence
7. Builtvisible – Best for Revenue-Impact Prioritization
Builtvisible takes a unique approach by modeling technical SEO optimizations based on potential revenue impact, ensuring Core Web Vitals improvements deliver maximum business value.
Strengths: Revenue-focused optimization, data-driven prioritization
Best For: E-commerce companies focused on ROI-driven improvements
8. The SEO Works – Best for Custom Technical Audits
The SEO Works provides comprehensive technical audits with bespoke optimization strategies tailored to specific business goals and technical constraints.
Strengths: Custom audit approaches, business-aligned prioritization
Best For: Companies needing detailed technical assessments
9. Screaming Frog – Best for Tool-Based Analysis
Screaming Frog offers powerful crawling and analysis tools that provide deep insights into Core Web Vitals issues and technical SEO opportunities.
Strengths: Advanced crawling technology, comprehensive reporting
Best For: Companies preferring tool-based analysis and reporting
10. Distilled – Best for Strategic Technical Consulting
Distilled combines technical expertise with strategic consulting, providing both immediate Core Web Vitals fixes and long-term technical SEO strategy.
Strengths: Strategic approach, educational resources
Best For: Companies seeking both execution and knowledge transfer
11. Omniscient Digital – Best for AI-Driven Optimization
Omniscient Digital leverages artificial intelligence and machine learning to automate Core Web Vitals diagnostics and optimization recommendations.
Strengths: AI-powered analysis, scalable optimization processes
Best For: Tech-forward companies interested in automated solutions
12. DeepCrawl – Best for Enterprise Monitoring
DeepCrawl provides enterprise-grade monitoring and alerting for Core Web Vitals and technical SEO issues across large, complex websites.
Strengths: Continuous monitoring, enterprise scalability
Best For: Large websites requiring ongoing technical surveillance
13. Technical SEO Ltd – Best for Pure Technical Focus
Technical SEO Ltd offers deep technical expertise specifically focused on Core Web Vitals and site performance optimization without broader marketing services.
Strengths: Pure technical focus, specialized expertise
Best For: Companies needing only technical SEO services
14. Aira – Best for Collaborative Implementation
Aira excels at working closely with internal development teams to implement Core Web Vitals optimizations while building in-house capabilities.
Strengths: Collaborative approach, knowledge transfer
Best For: Companies with internal technical teams
15. Harpin Labs – Best for UX-Driven Optimization
Harpin Labs combines Core Web Vitals optimization with user experience design, ensuring technical improvements enhance overall user satisfaction.
Strengths: UX integration, conversion-focused improvements
Best For: Companies prioritizing user experience alongside technical performance
Agency Comparison: Core Web Vitals Expertise
| Agency | SaaS Expertise | E-commerce Focus | JavaScript Optimization | Enterprise Ready | Pricing Model |
|---|---|---|---|---|---|
| Single Grain | Excellent | Excellent | Advanced | Yes | Custom Strategy |
| WebFX | Good | Excellent | Good | Yes | Enterprise Contracts |
| Siege Media | Good | Excellent | Good | Partial | Project-Based |
| Onely | Excellent | Good | Excellent | Yes | Technical Consulting |
| NinjaPromo | Excellent | Good | Advanced | Partial | Custom Packages |
Real-World Core Web Vitals Success Stories
The most compelling evidence for agency selection comes from documented results. Beyond Swappie’s impressive mobile revenue increase, other notable successes include:
Arti&Mestieri Platform Migration: During their WordPress to Shopify migration, working with RichClicks, they implemented comprehensive Core Web Vitals optimization as part of their technical SEO strategy. The result was dramatically faster load times, improved user engagement with longer session durations, and increased conversion rates that drove overall revenue growth.
SaaS Growth Through Technical Excellence: All Cyber Solutions demonstrated exceptional results for multiple SaaS clients, particularly in cybersecurity and brand protection sectors. One cybersecurity SaaS client achieved 167% organic traffic growth and 111% more marketing qualified leads, while a brand protection SaaS client saw 159% traffic growth and 194% more MQLs. Another client grew daily visitors from 1,200 to 3,000 through disciplined Core Web Vitals optimization paired with comprehensive technical SEO.
These examples illustrate why partnering with an agency that understands both technical optimization and business outcomes is crucial for sustainable growth. Need help choosing the right partner? Get Your Custom Growth Strategy to get personalized recommendations.
Key Selection Criteria for Your Business
When evaluating technical SEO agencies for Core Web Vitals optimization, growth-stage companies should prioritize:
Industry Specialization: Look for agencies with proven experience in your specific sector. SaaS companies need partners who understand complex application architectures, while e-commerce businesses require expertise in product page optimization and mobile commerce performance.
Integration Capabilities: The best results come from agencies that integrate Core Web Vitals optimization with broader growth strategies. Technical improvements should connect directly to business outcomes through conversion optimization and user experience enhancement.
Measurement and Reporting: Ensure your chosen agency provides comprehensive reporting that connects technical metrics to business KPIs. You need visibility into how Core Web Vitals improvements impact organic traffic, conversion rates, and revenue generation.
Strategic Partnership Approach: Growth-stage companies benefit most from agencies that act as strategic partners rather than tactical executors. Look for agencies that understand your business model and can prioritize optimizations based on potential impact.
For insights into common technical SEO challenges that may be affecting your Core Web Vitals, review our comprehensive guide on 15 common on-site technical SEO issues that many agencies address as part of their Core Web Vitals optimization process.
What to Expect: Implementation Timeline and Process
Core Web Vitals optimization typically follows a structured timeline for meaningful results:
Weeks 1-2: Technical Audit and Discovery – Comprehensive analysis of current performance, identification of critical bottlenecks, and prioritization of optimization opportunities based on business impact.
Weeks 3-6: Initial Optimizations – Implementation of quick wins including image optimization, script optimization, and basic performance improvements that provide immediate Core Web Vitals improvements.
Weeks 7-12: Advanced Optimization – Deep technical work including server-side optimizations, advanced caching strategies, and complex JavaScript optimizations that require development collaboration.
Ongoing: Monitoring and Iteration – Continuous monitoring of Core Web Vitals metrics with iterative improvements based on real user data and changing business requirements.
The most successful implementations combine technical expertise with strategic business understanding. Agencies that can connect technical improvements to business outcomes consistently deliver superior results for growth-stage companies.
The Future of Core Web Vitals: AI-Powered Optimization
Leading agencies are increasingly leveraging artificial intelligence to enhance their Core Web Vitals optimization capabilities. This includes automated performance monitoring, predictive optimization recommendations, and dynamic resource loading based on user behavior patterns.
For companies interested in how AI is transforming SEO beyond just Core Web Vitals, explore our detailed analysis of 6 powerful ways to use AI for SEO in 2025, which covers the broader applications of artificial intelligence in search optimization.
This technological evolution means that the most forward-thinking agencies are not just fixing current Core Web Vitals issues but building systems that continuously optimize performance as user behavior and search algorithms evolve.
Making the Right Choice for Your Business Growth
Core Web Vitals optimization represents a critical investment in your website’s foundation for sustainable growth. The agencies featured in this analysis each bring unique strengths to addressing these technical challenges, but the best choice depends on your specific business context, technical requirements, and growth objectives.
For growth-stage SaaS, B2B services, and e-commerce companies, the ideal agency partner combines deep technical expertise with strategic business understanding. They should be able to not only improve your Core Web Vitals scores but also connect those improvements to meaningful business outcomes including increased organic traffic, higher conversion rates, and revenue growth.
Single Grain’s position as the top choice reflects their unique ability to integrate Core Web Vitals optimization with comprehensive growth strategies, making them particularly well-suited for companies seeking transformative rather than incremental improvements. However, other agencies may be better fits for specific technical requirements or budget constraints.
If you’re looking for additional technical SEO expertise, consider reviewing our dedicated technical SEO agency page for more detailed information about comprehensive technical optimization services.
The choice of technical SEO agency will significantly impact your website’s performance and business growth potential. Get Your Custom Growth Strategy to discuss your specific challenges and growth objectives with experts who understand how to translate Core Web Vitals improvements into measurable business results.
