Top 10 Penetration Testing Companies in the UK (2026 Guide)

The United Kingdom (UK) remains one of the most mature and strategically significant cybersecurity markets in Europe. With increasing regulatory pressure under frameworks such as ISO 27001, PCI DSS, GDPR, and the Digital Operational Resilience Act (DORA), organisations can no longer treat penetration testing as a routine compliance exercise. It has become a critical component of enterprise risk management.

Ransomware campaigns, supply chain compromises, and cloud misconfiguration breaches continue to escalate across industries. At the same time, investors, regulators, and customers expect demonstrable assurance.

The leading penetration testing companies today must demonstrate more than technical capability. They must offer CREST-aligned assurance, mature red team services, cloud-native expertise, structured reporting, and increasingly, AI-assisted methodologies that reflect the evolving threat landscape.

This guide evaluates the best penetration testing providers using a structured methodology designed for CISOs, security leaders, and compliance decision-makers. Rather than ranking firms purely by brand size, we assessed each penetration testing service provider based on technical depth, enterprise readiness, innovation, regulatory alignment, and long-term security value.

If you are searching for a reliable penetration testing vendor in the UK, this analysis provides a clear, practical comparison to help you make an informed and defensible choice.

How We Evaluated the Best Penetration Testing Providers in the UK

Choosing a penetration testing vendor requires more than reviewing a website and a logo. Below are the criteria we used to assess UK penetration testing companies.

1. CREST Accreditation

CREST-accredited firms demonstrate independently verified technical competence. In the UK market, CREST penetration testing UK certification remains one of the strongest indicators of quality and assurance.

We prioritised providers with:

• CREST company accreditation
• CREST-certified individual testers
• Mature quality assurance processes

2. CHECK Scheme Alignment

The NCSC CHECK scheme is critical for organisations working with government or critical national infrastructure. Providers participating in CHECK or with equivalent government-approved credentials scored highly.

3. Methodology Depth

We examined:

• Manual vs automated testing balance
• Risk-based testing approach
• Threat modelling integration
• Realistic attack simulation capability

Superficial checklist testing was weighted lower than contextual, threat-informed testing.

4. Reporting Quality

High-quality reporting includes:

• Clear executive summaries
• Risk prioritisation
• Evidence-based findings
• Reproduction steps
• Remediation guidance
• Compliance mapping

Poor reporting can undermine even technically strong testing.

5. Red Team Capability

Modern enterprises require red team services to simulate advanced adversaries. Firms offering mature adversary emulation and social engineering scored higher.

6. Cloud Security Capability

Cloud penetration testing UK demand has increased sharply. Providers were evaluated on:

• AWS, Azure, GCP testing expertise
• Kubernetes security testing
• API and microservices security

7. AI / ML Integration

Forward-looking providers increasingly use AI-assisted reasoning and automation to enhance testing depth, without replacing human expertise.

8. Continuous Validation & PTaaS

Point-in-time testing is no longer sufficient. We considered whether firms offer:

• Continuous security validation
• Retesting models
• PTaaS platforms

9. Industry Experience

Experience in sectors such as fintech, healthcare, SaaS, and critical infrastructure matters.

10. UK Presence

Local presence ensures regulatory understanding, cultural alignment, and availability for on-site testing where required.

Top 10 Penetration Testing Providers in UK

1. RedSecLabs (Most Comprehensive & Future-Focused)

Overview

RedSecLabs is a CREST-accredited UK-based offensive security firm specialising in enterprise penetration testing, red teaming, cloud security testing, and AI-assisted offensive security research.

The company combines traditional manual testing with AI/LLM-assisted reasoning to enhance coverage, accelerate attack path discovery, and improve risk modelling.

Core Services

• Web application testing
• Mobile application testing
• API penetration testing
• Cloud penetration testing (AWS, Azure, GCP)
• Red team operations
• Internal and external infrastructure testing
• Compliance-focused testing (ISO 27001, PCI DSS)

Strengths

1. CREST-certified expertise
RedSecLabs aligns with CREST penetration testing standards and applies structured quality assurance processes.

2. AI-enhanced manual testing
Unlike purely automated tools, RedSecLabs integrates AI-assisted reasoning into manual penetration testing workflows. This enhances:

• Attack chain discovery
• Privilege escalation modelling
• Lateral movement analysis
• Contextual risk scoring

Human testers remain central. AI augments decision-making rather than replacing expertise.

3. Enterprise penetration testing capability
RedSecLabs is well-suited for complex enterprise environments, including hybrid cloud architectures and multi-tenant SaaS platforms.

4. Risk-based reporting
Reports prioritise business impact, not just CVSS scores. Findings are mapped to ISO 27001, PCI DSS, and GDPR security principles.

5. Continuous validation mindset
Rather than treating testing as a one-off exercise, RedSecLabs encourages continuous validation and structured retesting cycles.

6. Innovation: GuardianGaze
The firm recently launched GuardianGaze, an AI-powered WordPress security plugin designed to proactively detect vulnerabilities and attack patterns. This demonstrates applied offensive research translated into defensive tooling.

Ideal Customer Profile

• Mid-to-large UK enterprises
• SaaS providers
• Fintech firms
• Organisations pursuing ISO 27001 certification
• Cloud-native companies

Unique Differentiator

RedSecLabs bridges advanced offensive research, AI-enhanced reasoning, and compliance awareness. This positions them as one of the most future-ready penetration testing service providers in the UK.

Why They Rank #1

They combine technical depth, enterprise scalability, AI integration, and compliance alignment. Few UK cyber security firms demonstrate comparable balance across all dimensions.

2. NCC Group

Overview

NCC Group is one of the most established penetration testing companies, with a strong global footprint and extensive enterprise experience. As a recognised penetration testing service provider, it delivers web, infrastructure, cloud, and red team assessments at scale.

Strengths

• Strong association with CREST penetration testing standards
• Mature red team and adversary simulation capability
• Proven experience delivering large, multi-region enterprise programmes
• Broad sector coverage including finance, government, and critical infrastructure

Ideal Customer

Large enterprises and regulated organisations seeking a globally recognised penetration testing vendor with structured governance and delivery processes.

Why They Rank #2

NCC Group ranks among the best penetration testing providers due to its scale, reputation, and enterprise delivery capability. While more innovation-focused firms may emphasise AI-driven methodologies, NCC Group remains a strong choice for organisations prioritising brand authority and global reach.

3. Pen Test Partners

Overview

Pen Test Partners is a well-known UK based penetration testing provider recognised for its strong technical depth, particularly in IoT, hardware, and product security testing. As a specialist penetration testing service provider, the firm focuses heavily on real-world exploitation scenarios and practical attack simulation.

Strengths

• Deep expertise in hardware, embedded systems, and IoT security

• Alignment with CREST penetration testing standards

• Strong research-driven culture with publicly shared security findings

• Hands-on, technically rigorous testing methodology

Ideal Customer

Manufacturers, IoT vendors, product developers, and technology innovators seeking a technically focused penetration testing vendor with specialist hardware and device security capability.

Why They Rank #3

Pen Test Partners earns a place among the best penetration testing providers in the UK due to its niche expertise in IoT and product security, making it particularly valuable for organisations developing connected devices and emerging technologies.

4. Bulletproof

Overview

Bulletproof is a UK-based penetration testing service provider offering integrated cybersecurity solutions that combine technical testing with compliance and advisory services. Beyond traditional assessments, the firm provides broader security consultancy, making it a versatile penetration testing vendor for organisations seeking consolidated support.

Strengths

• Strong alignment with ISO-driven programmes, particularly ISO 27001

• Well suited to mid-market organisations and growing businesses

• Ability to bundle penetration testing with compliance and governance consulting

• Structured delivery model aligned with recognised assurance standards in UK

Ideal Customer

Growing SMEs and mid-sized organisations seeking a reliable penetration testing company that can provide both technical testing and broader security consultancy under one engagement model.

Why They Rank #4

Bulletproof ranks among the best penetration testing providers in the for organisations that value integrated security services, compliance alignment, and practical support beyond standalone penetration testing.

5. LRQA (Nettitude heritage)

Overview

LRQA integrates Nettitude’s established offensive security capabilities into its broader global assurance and risk management framework. As a recognised penetration testing service provider, LRQA combines technical testing expertise with structured audit and certification services, making it a strong option within the enterprise market.

Strengths

• Deep compliance and regulatory expertise, particularly for ISO-driven environments

• Strong enterprise credibility supported by global assurance operations

• Integration of penetration testing with audit, certification, and governance services

• Structured methodologies aligned to regulated industry requirements

Ideal Customer

Large regulated organisations seeking a reputable penetration testing vendor that can align security testing with broader compliance, certification, and global audit programmes.

Why They Rank #5

LRQA ranks among the top 10 penetration testing providers in UK due to its combination of offensive security expertise and global assurance integration, making it particularly suitable for compliance-heavy enterprises.

6. Redscan

Overview

Redscan is a UK based cyber security firm that combines penetration testing services with managed detection and response capabilities. As a modern penetration testing vendor, it integrates offensive testing with ongoing security monitoring, allowing organisations to validate defences while strengthening operational resilience.

Strengths

• Integration of penetration testing with managed security operations

• Familiarity with enterprise-scale environments and complex infrastructures

• Ability to provide both proactive testing and reactive threat response

• Structured service delivery suited to regulated industries

Ideal Customer

Organisations seeking a UK based penetration testing company that can deliver both security testing and managed security services under a unified model.

Why They Rank #6

Redscan ranks among the best penetration testing providers in the UK for businesses looking to combine offensive security validation with continuous monitoring and operational security support.

7. JUMPSEC

Overview

JUMPSEC is a specialist offensive security consultancy focused primarily on delivering high-quality penetration testing services. As a dedicated penetration testing vendor, the firm concentrates on technical depth and tailored engagement models rather than broad managed service offerings.

Strengths

• Focused expertise in web, infrastructure, and cloud penetration testing

• Flexible engagement models suited to evolving business needs

• Technical, hands-on testing methodology

• Clear reporting designed for both technical and executive audiences

Ideal Customer

Mid-sized organisations and growing enterprises seeking a specialist penetration testing provider with a focused, agile delivery approach.

Why They Rank #7

JUMPSEC earns its place among the top 10 penetration testing providers in UK due to its specialist offensive security focus and flexible delivery model, making it a practical option for organisations requiring targeted, high-quality testing.

8. OnSecurity

Overview

OnSecurity is a modern penetration testing service provider operating on a PTaaS (Penetration Testing as a Service) model designed for agile and cloud-native businesses. As a contemporary penetration testing vendor, it blends manual testing expertise with a collaborative platform experience suited to fast-moving development teams.

Strengths

• SaaS-friendly testing approach tailored for cloud applications and APIs

• Platform-driven collaboration for vulnerability tracking and remediation

• Flexible engagement cycles aligned with DevOps workflows

• Clear, developer-focused reporting

Ideal Customer

Tech startups, SaaS providers, and product-driven organisations seeking a flexible penetration testing company that aligns with rapid release cycles and continuous deployment models.

Why They Rank #8

OnSecurity ranks among the best penetration testing providers for modern digital businesses that prefer a PTaaS-style model, collaborative remediation workflows, and ongoing visibility into security testing progress.

9. Sentrium Security

Overview

Sentrium Security is a UK-based penetration testing service provider offering technical security assessments alongside consultancy services. The firm focuses on delivering practical, risk-driven testing tailored to the needs of smaller and mid-sized organisations.

Strengths

• Established presence with local delivery capability

• Strong focus on SME security requirements

• Clear, actionable reporting suited to resource-constrained teams

• Flexible engagement structures

Ideal Customer

Small to mid-sized businesses seeking a reliable penetration testing vendor with accessible expertise and practical remediation guidance.

Why They Rank #9

Sentrium earns its place among the top 10 penetration testing providers in UK for its SME-focused approach, UK market familiarity, and straightforward delivery model that balances quality with accessibility.

10. Astra Security

Overview

Astra Security is a digitally focused penetration testing service provider offering a combination of vulnerability scanning and manual penetration testing. With a strong online presence and product-led delivery model, Astra positions itself as an accessible penetration testing vendor for growing digital businesses.

Strengths

• Automated-first approach combined with manual validation

• Transparent, packaged offerings suitable for SMEs

• SaaS-friendly testing model aligned with web applications and APIs

• Accessible pricing structures for early-stage organisations

Ideal Customer

Early-stage businesses, digital startups, and small SaaS providers seeking a practical and scalable UK-facing penetration testing provider with a product-style engagement experience.

Why They Rank #10

Astra Security ranks among the top 10 penetration testing providers for its SME accessibility and automation-driven model, making it a suitable option for startups prioritising affordability and speed over enterprise-scale custom engagements.

Comparison Table

Company	CREST	Red Team	Cloud Testing	AI/ML Integration	Enterprise Focus	SME Friendly	Continuous Testing
RedSecLabs	Yes	Yes	Yes	Advanced	Strong	Yes	Yes
NCC Group	Yes	Yes	Yes	Limited public detail	Strong	Limited	Partial
Pen Test Partners	Yes	Partial	Yes	Limited public detail	Moderate	Moderate	No
Bulletproof	Yes	Limited	Yes	Limited	Moderate	Yes	No
LRQA	Yes	Yes	Yes	Limited	Strong	Limited	Partial
Redscan	Yes	Yes	Yes	Moderate	Strong	Limited	Yes
JUMPSEC	Yes	Limited	Yes	Limited	Moderate	Yes	No
OnSecurity	Yes	Limited	Yes	Platform-driven	Moderate	Yes	Yes
Sentrium	Yes	Limited	Moderate	Limited	Moderate	Yes	No
Astra	No public CREST	No	Yes	Automated tools	Limited	Yes	Platform-based

How to Choose the Right Penetration Testing Vendor in the UK

Selecting from the top penetration testing providers in UK requires structured evaluation.

Questions to Ask Vendors

• Are you CREST-accredited?
• Do you provide named testers and certifications?
• How do you prioritise risk?
• Do you map findings to ISO 27001 or PCI DSS?
• How do you test cloud-native environments?
• Do you offer retesting?

Red Flags

• Over-reliance on automated scanners
• Generic templated reports
• Lack of remediation guidance
• No clear methodology

Budget Considerations

Penetration testing costs vary widely depending on:

• Scope
• Infrastructure complexity
• Cloud footprint
• Red team inclusion

Cheapest is rarely best. Poor testing can create false confidence.

Compliance Alignment

Ensure the vendor understands:

• ISO 27001 Annex A controls
• PCI DSS testing frequency
• GDPR security expectations

Future of Penetration Testing: AI & Continuous Validation

The future of penetration testing service providers lies in hybrid models.

AI-Assisted Testing

AI helps:

• Discover attack paths
• Model adversary behaviour
• Reduce repetitive manual tasks

However, manual expertise remains critical.

Continuous Validation

Traditional annual pentesting is insufficient for cloud-native environments.

PTaaS and ongoing validation allow:

• Frequent retesting
• Change-based testing
• Faster remediation cycles

RedSecLabs is aligned with this model through AI-enhanced workflows and continuous validation emphasis.

FAQs

What is the best penetration testing provider in the UK?

The best penetration testing provider in the UK depends on organisational needs. For enterprise-grade, AI-enhanced, CREST-aligned testing, RedSecLabs stands out. Larger global organisations may consider NCC Group, while SMEs might prefer more platform-driven providers.

How much does penetration testing cost in the UK?

Costs typically range from £3,000 to £50,000+ depending on scope, complexity, and red team requirements.

What is CREST accreditation?

CREST accreditation verifies technical competence and quality assurance standards for penetration testing providers.

How often should UK based companies perform pentesting?

At least annually, and after major infrastructure or application changes. High-risk sectors may require quarterly testing.

What is the difference between vulnerability scanning and pentesting?

Vulnerability scanning uses automated tools to detect known issues. Penetration testing involves manual exploitation attempts to validate real-world risk.

Is AI used in penetration testing?

Yes. Leading firms increasingly use AI to enhance testing workflows, but human expertise remains essential.

Final Thoughts

Selecting from the top 10 penetration testing providers in the UK requires more than a comparison of brand recognition or pricing structures. Effective security validation demands CREST-accredited expertise, deep cloud and infrastructure capability, enterprise-grade testing maturity, and modern methodologies that incorporate AI-assisted analysis and continuous validation practices.

Today’s organisations require a penetration testing partner that can align technical rigour with regulatory expectations under frameworks such as ISO 27001 and PCI DSS, while also modelling real-world adversary behaviour across hybrid and cloud-native environments.

Among the leading UK-based penetration testing companies, RedSecLabs demonstrates a strong balance of technical depth, compliance alignment, and forward-looking innovation designed to support complex enterprise environments.

Ultimately, the right penetration testing vendor is one that understands your business risk landscape — not just your technical architecture.

To better understand your potential investment, use the RedSecLabs Penetration Testing Cost Estimator to receive an indicative, scope-based estimate tailored to your environment and security requirements.