API Penetration Testing Providers
API penetration testing focuses on the security of application programming interfaces, which form the backbone of modern web and mobile applications. Testers systematically evaluate REST APIs, GraphQL endpoints, SOAP services, and WebSocket connections for vulnerabilities including broken authentication, excessive data exposure, injection attacks, improper rate limiting, mass assignment, and broken object-level authorisation (BOLA).
Testing follows the OWASP API Security Top 10 and examines how APIs handle authentication tokens, enforce authorisation between users, validate input data, and protect against abuse.
API pen testing is increasingly important as organisations adopt microservices architectures, expose APIs to partners and third parties, and build API-first products. Insecure APIs are a leading cause of data breaches, making thorough security testing essential. API pen testing helps organisations that must comply with PCI DSS, HIPAA, SOC 2, and GDPR by identifying vulnerabilities that could lead to unauthorised data access or manipulation through API endpoints.
Aardwolf Security
Boutique UK penetration testing consultancy in Milton Keynes specialising in manual, expert-led security assessments across web applications, APIs, cloud, and mobile platforms.
Aon Cyber Solutions
Cybersecurity consulting division of global insurance leader Aon, uniquely combining penetration testing with cyber risk quantification and insurance expertise.
Aristi
CHECK and CREST-accredited Birmingham-based cyber security consultancy with over 15 years of experience delivering penetration testing, red teaming, and OT security assessments for government and private sector clients.
Bishop Fox
Premier US-based offensive security firm known for elite penetration testers, cutting-edge research, and the Cosmos continuous attack surface management platform.
Black Hills Information Security
Community-driven penetration testing firm known for free security education, open-source tools, Wild West Hackin' Fest, and practical offensive security services.
Blaze Information Security
CREST-accredited boutique pen testing firm with offices across Europe and Brazil, serving 200+ organisations in 25 countries.
BreachLock
Cloud-based Penetration Testing as a Service platform combining AI-driven automation with expert manual testing at accessible price points.
Bridewell
Fast-growing CREST and CHECK-accredited UK cybersecurity consultancy with deep expertise in critical national infrastructure sectors.
Bugcrowd
Leading crowdsourced security platform offering managed bug bounty programs and crowd-powered penetration testing with hundreds of thousands of ethical hackers.
Bulletproof
CREST-accredited UK cybersecurity and compliance provider offering penetration testing, managed security services, and regulatory consultancy to over 2,000 customers from its Stevenage headquarters.
Claranet
CREST and CHECK-accredited European managed services provider delivering penetration testing with deep infrastructure and cloud hosting expertise.
Coalfire
Compliance-focused cybersecurity advisory firm and FedRAMP 3PAO specializing in penetration testing that meets stringent regulatory requirements.
Cobalt
Pioneer of Pentest as a Service, delivering fast, platform-based penetration testing with a vetted global community of security researchers.
CovertSwarm
Subscription-based offensive cybersecurity firm delivering continuous cyber attack services with CREST STAR and CBEST accreditations from its London headquarters.
Cure53
Berlin-based specialists in web security, browser security, and cryptographic auditing, trusted by the world's leading VPN providers and privacy tools.
Cyberis
CREST and CHECK-accredited UK penetration testing consultancy with CBEST approval, specialising in infrastructure, application, and simulated attack assessments across the public and private sectors.
Cyphere
CREST-accredited Manchester-based cyber security firm delivering penetration testing, managed security services, and compliance consultancy across the UK, Europe, and the USA.
Dionach
Global enterprise cybersecurity consultancy founded in 1999 in Oxford, holding rare CREST STAR-FS accreditation and delivering penetration testing, red and purple teaming, and PCI QSA services across five international offices.
Equilibrium Security
CREST-accredited Birmingham-based cyber security consultancy delivering penetration testing, social engineering assessments, and Cyber Essentials certification for public and private sector clients.
Evalian
CREST-accredited UK cyber security and data protection consultancy offering penetration testing, ISO consultancy, and managed SOC services from offices across the UK and Ireland.
HackerOne
World's largest ethical hacker platform with over one million researchers, offering bug bounties and structured penetration testing to the US DoD and Fortune 500.
Integrity360
CREST-accredited pan-European cybersecurity services provider delivering penetration testing and managed security from Dublin with a strong UK and Ireland presence.
IOActive
Elite boutique security consultancy specializing in IoT, SCADA/ICS, embedded systems, and hardware security research with world-renowned researchers.
JUMPSEC
Full-service London-based cybersecurity consultancy with CREST, CHECK, and NCSC accreditations delivering offensive testing, managed detection, and strategic advisory services.
Komodo Consulting
Tel Aviv-based offensive security consultancy leveraging Israel's deep cybersecurity talent for pen testing, red teaming, and threat intelligence.
LRQA
The only organisation worldwide with a full suite of CREST accreditations. 250+ cybersecurity specialists operating in 55+ countries across pen testing, red teaming, and incident response.
Mandiant
World-renowned cybersecurity firm now part of Google Cloud, delivering threat intelligence-led penetration testing and red teaming informed by front-line incident response experience.
NCC Group
Global cybersecurity consultancy with CREST, CHECK, and CBEST accreditation, renowned for deep technical research and comprehensive penetration testing services.
NetSPI
Leading penetration testing firm with the Resolve platform for continuous attack surface management, trusted by nine of the top ten US banks.
Nettitude
CREST, CHECK, and CBEST accredited UK consultancy within Lloyd's Register, delivering premium penetration testing for government and critical infrastructure.
Offensive Security
Creators of OSCP, Kali Linux, and Exploit-DB, offering elite penetration testing services from the team that trains the world's ethical hackers.
OnSecurity
CREST-accredited, platform-driven penetration testing vendor in Bristol offering AI-augmented testing with rapid self-service booking for over 400 global customers.
Packetlabs
Canada's most reviewed cybersecurity company. CREST-certified, SOC 2 Type II-attested pen testing from Toronto.
Pen Test Partners
The UK's largest independent security testing firm, renowned for IoT/OT research, CBEST red teaming, and CHECK/CREST-accredited penetration testing across all sectors.
Penetration Testing ME
Dubai-based CREST and ISO certified pen testing specialist serving the GCC region with full VAPT services.
Pentest People
CREST and CHECK-accredited UK penetration testing firm with an innovative SecurePortal platform and transparent pricing for mid-market organizations.
Praetorian
Offensive security firm founded by former DoD professionals, offering elite penetration testing and the Chariot continuous attack surface management platform.
PwC Cyber Security
Global Big Four professional services firm delivering CREST, CHECK, and CBEST-accredited penetration testing and red teaming services from London, serving the UK's largest enterprises and regulated organisations.
Rapid7
Creators of Metasploit offering enterprise penetration testing integrated with their comprehensive vulnerability management and security operations platform.
Raxis
Gartner-recognised PTaaS provider with 14+ years of experience. Expert-led pen testing combining manual techniques with AI-powered tooling across web, cloud, mobile, and SCADA/ICS.
Redbot Security
Denver-based boutique pen testing firm with senior-only testers. Personalised engagements across penetration testing, red teaming, and vulnerability management.
Redscan (A Kroll Business)
London-based cybersecurity provider, now part of Kroll, delivering CREST-accredited penetration testing, managed detection and response, and incident response with a 550-strong cyber team.
RedSecLabs
CREST-certified and PCI QSA penetration testing consultancy in London, delivering offensive security and compliance services across 25+ countries with research-driven expertise.
Rhino Security Labs
Cloud security penetration testing specialists known for the Pacu AWS exploitation framework and deep expertise across AWS, Azure, and GCP environments.
Salus Cyber
Award-winning Cheltenham-based cybersecurity consultancy with NCSC CHECK Green Light status and CREST approval, specialising in defence, government, and critical national infrastructure security.
SEC Consult
Leading European cybersecurity consultancy from Vienna with a prolific vulnerability research program and deep expertise in IoT and embedded systems security.
SECFORCE
Leading UK offensive security consultancy based in Canary Wharf, delivering CREST-accredited penetration testing and adversary simulation to organisations with the most demanding security requirements.
Secureworks
Dell Technologies-backed cybersecurity firm with elite Counter Threat Unit intelligence informing enterprise penetration testing and adversary simulation.
Securin
Vulnerability intelligence-driven penetration testing firm providing contextual security assessments informed by threat actor exploitation data and ransomware tracking.
Securing (SecuRing)
Poland's longest-running independent pen testing firm with 50+ consultants. Specialises in application security, cloud testing, and red teaming.
Sencode
CREST-accredited North East England penetration testing specialist founded in 2019, offering accessible and transparent security testing with free retests and a strong focus on social engineering.
Shielder
Independent Italian offensive security firm specialising in web, mobile, network, and embedded security assessments with a strong research focus.
Swascan
Italian cloud-based security testing firm offering black, white, and grey box pen testing with strong European compliance expertise.
Synack
FedRAMP-authorized crowdsourced penetration testing platform combining vetted elite hackers with AI-powered Hydra technology for continuous security testing.
Tevora
CREST-accredited California consultancy blending compliance expertise with penetration testing. First to earn ISO 17020 for MITRE ATT&CK and PTES frameworks.
ThreatSpike Red
London-based cybersecurity firm offering unlimited, fixed-price penetration testing and red teaming services with ISO 27001 certification and a unique subscription model.
Trail of Bits
Elite security research firm specializing in source code review, blockchain auditing, and building industry-standard open-source security tools.
TrustedSec
Elite offensive security firm founded by a former NSA operator, delivering CREST-accredited penetration testing, red teaming, and adversary simulation to Fortune 500 and government clients.
Trustwave
Global managed security provider with the elite SpiderLabs penetration testing team and deep PCI DSS compliance expertise.
Vumetric (TELUS)
ISO 9001-certified Canadian pen testing firm conducting 500+ tests annually. Now part of TELUS, serving Fortune 1000 to SMBs.
WithSecure
Leading European cybersecurity firm offering penetration testing with deep expertise in EU regulatory compliance including GDPR, NIS 2, and TIBER-EU.
API Penetration Testing FAQs
What types of APIs can be tested?+
REST, GraphQL, SOAP, gRPC, WebSocket, and any custom API protocols can be tested. Testers need API documentation or access to the application that consumes the API.
Do you need API documentation for testing?+
API documentation (Swagger/OpenAPI specs, Postman collections) helps testers work more efficiently but is not strictly required. Testers can discover and map API endpoints through application analysis.
How is API pen testing different from web app pen testing?+
API pen testing focuses specifically on the API layer - authentication, authorisation, data validation, and business logic at the API level. Web app testing covers the full application including the user interface.