Top 10 API VAPT Service Providers in the United Kingdom
Who Are the Best API VAPT Providers in the UK?
UK options range from specialist testers such as NCC Group to large consultancies and CyberSapiens, so choose on credentials rather than brand. Look for CREST accreditation, add NCSC CHECK if you test government or critical national infrastructure systems, and ask for testing against the OWASP API Security Top 10 with a retest included.
Why API VAPT Matters for UK Organisations
APIs connect your apps, partners and customers, so one weak endpoint can expose data without anyone touching your network. API vulnerability assessment and penetration testing (VAPT), also called API security testing, finds and proves those weaknesses before attackers do.
What API VAPT Covers
Find the weaknesses
Tools scan your endpoints for known flaws such as weak authentication, missing rate limits and misconfiguration.
Prove the impact
Testers exploit flaws by hand, including authorisation and business logic issues that scanners often miss.
Three Things to Know First
43% of UK businesses
The UK government’s Cyber Security Breaches Survey 2025/26 found that 43% of businesses identified a breach or attack in the previous 12 months, rising to 65% of medium and 69% of large businesses.
UK GDPR and authorisation
The UK GDPR expects appropriate security for personal data. Every test needs written authorisation, because unauthorised access can breach the Computer Misuse Act 1990.
OWASP API Top 10
The OWASP API Security project is the standard reference for what a tester should cover, from broken authorisation to unsafe use of third-party APIs.
How We Chose the Providers
CyberSapiens publishes this list and ranks itself first. We looked at accreditation, API testing depth and delivery model for each provider, and each entry is labelled so you can see who does what. Always confirm a provider’s CREST and CHECK status in the official directories before you sign.
List of Top 10 API VAPT Service Providers in the United Kingdom
1. CyberSapiens: Best API Security Testing Service Provider in UK
CyberSapiens provides API VAPT that combines manual and automated testing to find the hidden flaws that scanners miss, with a methodology tailored to each client’s APIs. Our API VAPT service is part of our wider vulnerability assessment and penetration testing offering.
Why Organisations Choose CyberSapiens
Experienced testers
Security professionals experienced in API testing, vulnerability assessment and penetration testing across industries.
Full-picture testing
Review of your API’s architecture, design and implementation, not just its endpoints.
Tailored methodology
A testing plan built around your security objectives and the constraints of your API.
3. Pen Test Partners
A research-led specialist that names API testing, application code review and mobile testing among its services, alongside CHECK work, PCI QSA status and CBEST testing.
Best for: teams that want manual-first API testing from a specialist.
4. KPMG UK
KPMG LLP is an NCSC-certified CHECK company and is listed on CREST for penetration testing and threat-led testing. Its services range from vulnerability assessments to red teaming.
Best for: organisations that want testing tied into a wider risk programme.
5. PwC UK
Listed on CREST for penetration testing and threat-led testing, and an NCSC CHECK provider. It says it designs tests around real-world threat scenarios.
Best for: large organisations in regulated sectors.
6. Deloitte UK
Offers penetration testing within its wider cyber practice. Check its current CREST and CHECK status in the directories before you shortlist it.
Best for: organisations already working with Deloitte on risk and governance.
7. CGI UK
Its UK penetration testing team describes itself as a founding member of the NCSC CHECK scheme, and its CREST listing also covers incident response and a security operations centre.
Best for: public sector bodies and government suppliers that need CHECK delivery.
8. Orange Cyberdefense (formerly SecureData)
SecureData was acquired by Orange in 2019 and later rebranded as Orange Cyberdefense. It offers goal-oriented penetration testing alongside managed detection and response.
Best for: organisations that want testing and managed security from one provider.
9. LevelBlue (formerly Trustwave)
LevelBlue completed its acquisition of Trustwave in August 2025, and the SpiderLabs team now operates as LevelBlue SpiderLabs. Penetration testing sits within its offensive security portfolio.
Best for: organisations that want managed detection combined with offensive testing.
10. Portcullis (part of Cisco)
A long-established UK security consultancy acquired by Cisco in 2015. Its services include web application assessments and network penetration testing.
Best for: organisations that want testing from a long-established UK consultancy.
Verify before you sign: check each provider’s firm-level accreditation on the CREST Marketplace, ask for API testing to be named in the scope, and confirm that a retest is included.
Benefits of API VAPT Services
API VAPT gives UK organisations five practical benefits, from fewer breaches to stronger evidence for auditors and buyers.
Find the flaws scanners miss
Manual testing exposes broken authorisation and business logic flaws, such as one user reading another user’s records, before an attacker does.
Evidence for UK GDPR and PCI DSS
The ICO’s guide to data security says the UK GDPR requires a process for regularly testing your security measures, without fixing the type or frequency. A penetration test is a common way to show it, and PCI DSS also requires regular testing of in-scope systems.
Avoid the cost of a breach
IBM’s Cost of a Data Breach Report put the 2026 global average at $4.99 million. In March 2025 the ICO fined the software provider Advanced £3.07 million, with insufficient vulnerability scanning among the gaps it cited.
Give customers evidence
A recent test report, or a summary letter from your tester, answers security questionnaires with proof rather than promises.
Win and keep larger customers
Enterprise and public sector buyers often ask suppliers for testing evidence, so a clean, recent report can shorten supplier reviews.
FAQs
1. What is API VAPT?
API VAPT, also called API security testing, combines vulnerability assessment and penetration testing for APIs. Tools find known weaknesses, and testers then exploit them by hand to show the real impact on your data.
2. Why do I need API VAPT services?
APIs expose data and business functions directly, so one authorisation flaw can leak records without any network intrusion. The UK GDPR also requires a process for regularly testing your security measures, and customers increasingly ask for evidence.
3. What are the benefits of API VAPT services?
The main benefits are fewer exploitable flaws, evidence for UK GDPR and PCI DSS, lower breach risk and cost, stronger customer trust, and faster supplier security reviews.
4. How often should I perform API VAPT testing?
At least once a year, and after major changes such as new endpoints, authentication changes or big releases. PCI DSS sets a 12-month cadence for in-scope systems, and the UK GDPR leaves frequency to your risk assessment.
5. What is the difference between vulnerability assessment and penetration testing?
A vulnerability assessment lists potential weaknesses, usually with automated tools. Penetration testing goes further by simulating a real attack to prove which weaknesses can be exploited and what an attacker could reach.
6. How long does API VAPT testing take?
Typically a few days to a few weeks, depending on the number of endpoints, user roles and authentication methods. Allow extra time for reporting and for a retest once your team has fixed the findings.
7. What is the cost of API VAPT services?
Cost depends on scope: the number of endpoints and roles, how much manual testing you want, and whether a retest is included. Ask every provider to quote against a written endpoint list so you can compare offers fairly.
8. How do I choose an API VAPT service provider?
Look for CREST accreditation for commercial work, and NCSC CHECK if you test government or critical national infrastructure systems. Also ask for API testing to be named in the scope, a sample report and a retest policy.
9. What is the difference between API VAPT and traditional penetration testing?
API testing focuses on endpoints, tokens, object-level authorisation, rate limits and business logic, often without a user interface. Traditional network and system testing targets hosts, services and configurations.
10. Can I perform API VAPT testing in-house?
In-house testing is useful for regular checks, but it works best alongside an independent test. Auditors and customers often expect the objectivity of a third party.
Test Your APIs Before Attackers Do
Share your API scope and we will recommend the right depth of testing, mapped to the OWASP API Security Top 10. Read more about our API VAPT service before you get in touch.
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