The Best Web Application Penetration Testing Companies UK
The best UK web application penetration testing companies in 2026 are CREST-accredited firms that test business logic, authenticated user flows and APIs, not just an automated OWASP Top 10 scan. This guide compares 7 leading providers: Precursor Security, NCC Group, Pen Test Partners, Redscan (Kroll), JUMPSEC, OnSecurity, and Claranet Cyber Security, on criteria any buyer can check independently.
Seven CREST-accredited UK web application penetration testing companies compared on the criteria that actually matter to buyers: OWASP-depth authenticated testing, verifiable accreditation, pricing you can see before a sales call, and a retest policy that closes the loop.
We are Precursor Security, and we have ranked ourselves first on this list.
Rather than pretend otherwise, we publish the selection criteria in full, describe every competitor fairly, and link the independent CREST member directory so you can check our working. The firms below are genuinely good at web application testing. The differences are in delivery model, transparency, and who each firm serves best.
Seven firms, side by side
| Provider | CREST status | Pricing published | From |
|---|---|---|---|
| 1. Precursor Security | Pen Test + VA + SOC | Yes | From £3,750 |
| 2. NCC Group | Member firm | No | On application |
| 3. Pen Test Partners | Member firm | No | On application |
| 4. Redscan (Kroll) | Member firm | No | On application |
| 5. JUMPSEC | Member firm + NCSC CHECK | No | On application |
| 6. OnSecurity | Member firm | No | Instant quote via platform |
| 7. Claranet Cyber Security | Member firm + CREST OVS | No | On application |
Verified against each company's public website, September 2026. "No" means we could not find a published rate; it does not mean the firm lacks one.
The 7 best UK web application
penetration testing companies in 2026
1. Precursor Security
Precursor holds triple CREST accreditation across Penetration Testing, Vulnerability Assessment, and Security Operations Centre services, a combination held by fewer than 70 firms worldwide. Every tester is a UK-based, DBS-checked employee. Web application testing is priced on the website, from £3,750 at approximately £1,200 per consultant day, and covers OWASP Top 10 methodology, business logic, authenticated access control, and the APIs the application calls. A retest is included in every engagement and a written quote follows within 24 hours of scoping. For clients running both services, web app findings can feed directly into SOC detection rules under the closed-loop model.
Trade-off: A mid-market specialist rather than a global enterprise brand, and the youngest firm on this list.
2. NCC Group
NCC Group is one of the largest security consultancies in the world, headquartered in Manchester, with a deep research pedigree and the bench depth to staff large, multi-application testing programmes. For a FTSE-100 estate running many web platforms in parallel, few firms can match the capacity.
Trade-off: Engagement model and pricing are built for enterprise procurement. Costs are on application.
3. Pen Test Partners
Pen Test Partners are the UK's best-known specialists in embedded and operational technology: connected vehicles, ships, planes, industrial control systems, and consumer IoT. Their web application testing typically appears as part of a wider assessment that also covers the hardware, firmware, and mobile apps those platforms talk to, and their public research is consistently excellent and widely cited.
Trade-off: Standalone, general-purpose web application testing is not their distinctive strength; hardware and IoT are. Pricing on application.
4. Redscan (Kroll)
Redscan, now part of Kroll, pairs a large practitioner organisation with strong client review scores and the backing of a global incident response and forensics business. For organisations that want their web app tester, their IR retainer, and their forensics provider under one roof at enterprise scale, the Kroll relationship is the draw.
Trade-off: Pricing on application, and the engagement model leans enterprise.
5. JUMPSEC
JUMPSEC holds NCSC CHECK status alongside CREST membership, which makes them a strong choice for PSN-connected web portals and government platforms that mandate CHECK delivery for authenticated testing. Named private sector clients and published case studies add useful proof.
Trade-off: Pricing on application.
6. OnSecurity
OnSecurity runs a platform-first, pentest-as-a-service model with instant online quoting and quick scheduling for web application and API testing, and carries strong review scores on G2. For a SaaS platform that needs authenticated testing booked this week with minimal procurement friction, the platform model works well.
Trade-off: Quotes are generated through their platform rather than published as a rate card, and the model is optimised for smaller, repeatable web app scopes.
7. Claranet Cyber Security
Claranet holds CREST OVS (OWASP Verification Standard) accreditation specifically for its application security services, alongside CHECK and CREST penetration testing status, and delivers over 1,000 tests a year through a global managed services provider with more than 20 years in the market. Every report is CVSS-scored and peer-reviewed before delivery, and retesting of remediated findings is included as standard.
Trade-off: Pricing on application, and web app testing sits inside a broader managed-services relationship rather than as a standalone specialist offer.
How we ranked them
Six criteria, each specific to what a web application test actually needs to cover, and each something a buyer can verify without taking anyone's word for it.
Business logic flaws, authentication and session flows, and broken access control (IDOR) require a human tester reasoning about what the application is supposed to do. An automated scan cannot find them.
Modern web applications are powered by REST and GraphQL endpoints. A web app test that ignores the APIs the front end calls has not tested the application, only its interface.
Company accreditation in the CREST directory, and individual tester certification for web application testing specifically, not just an organisational badge.
Whether verification of your fixes is included or sold back to you afterwards as a second engagement.
A report needs reproduction steps a developer can action and an executive summary a compliance auditor or procurement team will accept without pushback.
Whether a firm treats web app testing as a one-off annual event or connects findings into ongoing monitoring. See our approach to closed-loop security.
Red flags when choosing
a web app pentest company
Whichever firm you choose, including us, walk away if you see these.
A DAST scan sold as a manual web app test
An automated DAST tool run overnight and repackaged as a penetration testing report will miss business logic and access control flaws entirely. Ask directly: how many days of manual testing, by whom, with what certifications?
Unauthenticated-only scope
Testing only the public, logged-out surface of a web application misses the vast majority of critical findings. Most serious vulnerabilities, IDOR, privilege escalation, business logic flaws, live behind the login screen and require authenticated (grey box) testing.
No business-logic testing
If a proposal lists only OWASP Top 10 categories with no mention of testing your application's specific workflows (checkout, approvals, role changes), the tester has not engaged with what your application actually does.
No retest
A web app pen test without verification of your fixes is half a service. If the retest is a separately priced second engagement, your remediation evidence for auditors and insurers costs double.
Per-page pricing games
Quotes based purely on page count or URL count ignore the complexity that actually drives testing time: number of user roles, API surface, and authentication flows. A ten-page application with five user roles takes longer to test properly than a hundred-page brochure site.
Reports that are raw scanner output
Ask for a redacted sample report before you buy. If it reads like an exported scanner log with no executive summary, business impact, or prioritised remediation, your developers and your board will get nothing from it.
UK web app pen test prices in 2026
Across the market, CREST-accredited testing runs £1,000 to £1,500 per consultant day. At Precursor's published rate of approximately £1,200 per day: a standard single-role web application from £3,750 over 3 to 5 days, a complex multi-role application from £6,250, and multi-application testing (portal, admin console and mobile backend together) from £8,750.
Full cost guide with worked examplesRelated pages worth reading next.
Web application penetration testing
CREST-accredited testing from £3,750: OWASP Top 10, business logic, API and SSO testing.
See the serviceAPI security testing
Deep-focus REST and GraphQL engagement: BOLA, mass assignment, broken object-level auth.
See API testingPenetration testing cost guide
UK day rates, scope multipliers, and worked web-app examples by complexity tier.
See cost guideClosed-loop security
How offensive findings feed defensive monitoring instead of sitting in a PDF.
See the modelBest penetration testing companies UK
The broader ranking, covering network, cloud and full-scope testing providers.
See the full rankingBest penetration testing for SaaS
Multi-tenant considerations for SaaS platforms choosing a testing provider.
See the SaaS guideCompare us against anyone on this list.
Fixed pricing published before you call. A written quote within 24 hours of a scoping conversation. Retest included.
Choosing a web app pen test company
The questions buyers ask most when comparing UK web application testing providers.
A UK web application penetration test typically costs from £3,750 for a small, single-role application to £8,750 or more for a complex, multi-role platform, with 3 to 5 days of testing being typical for a standard scope. Multi-application testing, for example a customer portal, admin portal and mobile app backend together, can run £8,750 to £13,750 or more. Across the CREST-accredited market, day rates generally sit between £1,000 and £1,500 per consultant day. Most firms on this list price on application; Precursor publishes web application rates from £3,750.
At least annually, and additionally after any significant release: a new authentication flow, a new payment journey, a major framework upgrade, or a new API surface. PCI DSS Requirement 11.4.2 requires testing of web-facing applications at least annually and after significant changes, and many cyber insurance policies now expect the same cadence for internet-facing applications.
A vulnerability scan is an automated check that matches software versions and known configuration issues against a database of CVEs. A web application penetration test is manual: an accredited tester works through the application as an unauthenticated visitor, then as a standard user, then as an admin, actively trying to access data or functions they should not be able to reach. That is how business logic flaws, broken access control, and privilege escalation chains get found, categories a scanner has no way to detect because they depend on understanding what the application is supposed to do, not just what software it runs.
Yes, all seven firms on this list test the APIs a web application calls as part of a standard web application engagement, covering issues like broken object-level authorisation (BOLA/IDOR), mass assignment, and rate-limiting failures. For a dedicated, deeper assessment of API endpoints that sit outside the web front end, a specialist API security testing engagement is a separate, more thorough scope.
Based on verifiable CREST accreditation, delivery model, and pricing transparency, the leading UK web application penetration testing companies are Precursor Security, NCC Group, Pen Test Partners, Redscan (Kroll), JUMPSEC, OnSecurity, and Claranet Cyber Security. Each suits a different buyer: Precursor for published fixed pricing and closed-loop monitoring, NCC Group and Redscan for enterprise scale, Pen Test Partners for hardware-adjacent estates, JUMPSEC for CHECK-mandated public sector work, OnSecurity for fast SaaS turnaround, and Claranet for CREST OVS-accredited application security within a global MSP relationship.