Best OnSecurity Alternatives (2026): UK PTaaS and Penetration Testing Firms Compared

OnSecurity bills penetration testing by the hour and says so on the record. Its pricing page states that "Our transparent, hourly billing means that everybody pays the same rate, and we quote to the nearest hour, not the nearest day", adds that "OnSecurity works in hours, not days, so you get a quote based on the actual time your test will take, without any padding or rounding up to the nearest day", and confirms free retesting inside a stated window plus no fee to cancel or reschedule. OnSecurity Technology Limited is registered at 1 Victoria Street, Bristol BS1 6AA and was incorporated on 20 June 2022; its CREST Marketplace listing shows 8 years of membership with a Penetration Testing accreditation, the CREST AI Charter and ISO 27001.

That is one of the cleanest commercial propositions in British penetration testing. This guide ranks eight alternatives and says plainly where OnSecurity is still the right answer. Every claim about OnSecurity below is drawn from its own pages, its Companies House record or its CREST Marketplace listing, and where a figure is not published we write "not published" rather than estimating.

Where Stingrai fits: Stingrai ranks first in this guide. Stingrai is a CREST-accredited penetration testing service provider at firm level, founded in 2021, headquartered in Toronto with a London office. Two named penetration testers run each human-led engagement, drawn from a team holding OSCE³, OSWE, OSEP, CREST CRT and CISSP, with 18 published CVEs and Halls of Fame at Apple, Google, the US Department of Defense and the US Federal Reserve. Web and API testing runs authenticated across every user role for broken authorisation, IDOR and business logic, alongside mobile, cloud, internal and external networks, Active Directory, social engineering and red teaming, delivered one-time or continuously through its PTaaS platform with live tester chat, Jira and Slack push, retesting and an attestation letter, at a published price of US$3,000 per assessment for one web application and associated APIs (pricing) and every other scope quoted.

At a Glance: OnSecurity and the Best Alternatives in 2026

All cells were verified on each vendor's own pages, on Companies House or on the CREST Marketplace on 5 September 2026. Source links appear in the full comparison table further down.

What OnSecurity Sells in 2026

One subscription, three things inside it, and a set of commercial terms that do most of the persuading.

The testing catalogue. Web application, mobile application, LLM and AI red teaming, cloud security across AWS, Azure and GCP, physical penetration testing, external and internal infrastructure, social engineering and phishing simulation.

The platform layer. External vulnerability scanning and threat intelligence with web scanning run continuously between tests, with the ability to "Decide which scanning features to run on each target" and to "Exclude noisy subdomains and tailor the platform to your environment".

The commercial terms, which are the differentiator:

• Hourly billing. "Everybody pays the same rate, and we quote to the nearest hour, not the nearest day."

• Free retesting. "OnSecurity will retest any findings you've fixed for free as long as it falls within the free retesting window."

• No cancellation fee. "We don't charge you any fees to cancel or reschedule a test."

• Real-time reporting. "Our testers report in real time as they test", and you "can chat directly to your tester in-platform or via Slack during the test."

• Instant quoting. "OnSecurity requires just several simple scoping questions to determine the scale of your test. We then use an algorithm to generate you an estimated quote in just a few clicks."

• One payment. "Combine pentesting and scanning into one monthly payment."

The positioning. OnSecurity describes "AI-augmented Pentesting: Human Expertise Where It Matters Most", claims "Saving 30 to 50% of manual effort for 500+ clients", up to a "95% reduction in vulnerability management time", identification of critical issues "40% faster", and states its founders spent "a collective 40 years as professional ethical hackers". It also states a clear methodological position: "We believe in manual-first testing, and investing in developing talent through a structured and rigorous training programme."

Why Buyers Look for OnSecurity Alternatives

None of these are defects. They are consequences of a focused, product-led model at a specific company size, and all four are verifiable on OnSecurity's own pages or its CREST listing.

1. Transparent billing is not the same as a published price. The hourly commitment is genuinely unusual and genuinely useful. But there is no rate card on the pricing page: no hourly figure, no starting price, no tier table. The instant quote tool returns a number after you answer scoping questions, so you still cannot put a line in a budget from the public site alone.

2. The accreditation set is one CREST discipline. The CREST Marketplace listing shows Penetration Testing, plus the CREST AI Charter and ISO 27001. There is no NCSC CHECK provider status, no Threat Led Penetration Testing accreditation, and no Bank of England CBEST or STAR-FS partner assurance. For UK public-sector data or systemically important financial institutions, those schemes are the gate, and OnSecurity does not clear them.

3. The technical bench is small by design. The same CREST listing records 50 to 99 employees with 11 to 25 technical staff. That is a deliberate quality-control choice and it matches the "manual-first testing" position, but it is a real capacity ceiling if you need several concurrent engagements across a large estate on a fixed audit date.

4. Remediation automation is not published. Real-time reporting and direct tester access via Slack are strong remediation aids. What is not published on any OnSecurity page is automatic generation of fix pull requests, or a gating check that blocks a vulnerable merge. Engineering-led teams increasingly want the patch proposed in the pull request rather than a finding in a portal.

What Testing Actually Surfaces

Very few providers publish outcome data from their own engagements, which makes the shape of a real finding set hard to reason about during procurement. Stingrai's State of Penetration Testing 2026 analyses 1,206 verified findings across 55 penetration tests. Three numbers matter here. 92.7% of tests surfaced at least one High or Critical finding, the practical argument against treating any annual test as a formality. The false-positive rate across those findings was 0.74%, the benchmark to hold any AI-augmented vendor to when it tells you validation is handled. And the median time to fix a Critical was 10.5 days, which is why real-time reporting and pull-request-level remediation are worth pricing rather than treating as a nice-to-have.

The 8 Best OnSecurity Alternatives in 2026

1. Stingrai

World-Class Offensive Security.

Stingrai is a global CREST-accredited penetration testing services company founded in Toronto, Canada in 2021, trusted by companies from startups to enterprises to meet audit requirements for SOC 2, ISO 27001, CMMC, PCI DSS and HIPAA. OSCE³, OSWE, OSEP, CREST CRT certified pentesters, who are also world-class security researchers and bug bounty hunters. Choose from fully human-led or hybrid (AI agents plus human penetration testers) engagements across web, API, mobile, AI and LLM, cloud, network, Active Directory and social engineering penetration tests and red team engagements.

Its London office is at 1 Coldbath Square, Farringdon. Where OnSecurity sells hours, Stingrai sells a scoped engagement at a published price with two named penetration testers on it, reviewed by a team lead with 16 years in penetration testing and exploit development. The bench has published 18 CVEs and appears in the bug bounty Halls of Fame of Apple, Google, the US Department of Defense and the US Federal Reserve, including a founding member of Uber's offensive security team. Explore the PTaaS platform.

Depth, not breadth of tooling, is the argument. On a web application the testers work authenticated across every user role rather than a single session, hunting broken authorisation and IDOR between roles and tenants, business logic abuse, injection and session handling against the OWASP Top 10 and ASVS, with source-assisted review where repository access is granted. On infrastructure they cover the external perimeter, internal lateral movement and privilege escalation, Active Directory attack paths and segmentation boundaries. Findings are chained into real attack paths and documented with a working proof of concept.

Stingrai delivers both one-time annual penetration tests and continuous programmes that test every release, on the same two published tiers.

Services and scope

• Application security: web applications and APIs, mobile applications, and AI and LLM systems.

• Network and cloud security: internal and external networks, Active Directory, Wi-Fi, and cloud environments.

• Social engineering: phishing campaigns and physical security assessments.

• Adversary simulation: red teaming and purple teaming.

Delivery and evidence

Findings post to the PTaaS portal as they are confirmed, each with a proof of concept and prioritised remediation guidance, with live chat to the assigned penetration testers during the test and push into Jira, GitHub or Slack. Retesting of remediated findings is included rather than bounded by a window, and every human-led and hybrid engagement ends with a redactable report, an attestation letter and a verified badge for customer security reviews. CREST accreditation applies to Stingrai as a penetration testing service provider; it is separate from individual tester certifications.

Where Snipe fits

Snipe is Stingrai's autonomous agent for web application penetration testing, including the application's APIs. It runs black-box, authenticated grey-box across roles and white-box source review, hunts IDOR, broken authorisation and business logic rather than known-class bugs alone, opens AutoFix pull requests and gates merges on every pull request. It works alone on the Autonomous tier, or on Hybrid where penetration testers test alongside it throughout. Mobile, AI and LLM, cloud, network, social engineering and red and purple team work is scoped with penetration testers.

Pricing and fit: Published Autonomous and Hybrid packages cover one web application and associated APIs, at US$3,000 per assessment or US$650 per month, and US$6,800 or US$1,275 per month. Request a scoped quote for networks, cloud, mobile or red team scopes. Best for the OnSecurity buyer who wants a price before a scoping call, fix automation in the pull request, and business logic and authorisation depth from named certified testers, one-time or continuous.

2. NCC Group

Manchester and global. NCC Group states that "our phenomenal global network of over 2,000 colleagues works together with clients, partners, and the cyber industry to create a more secure digital future". Its penetration testing services span application security, network testing, cloud, hardware, blockchain, cryptographic services and continuous testing, its accreditation set includes NCSC CHECK, CREST, UKAS and Cyber Scheme, and it publishes "1000+ days dedicated to research annually" against "testing methodologies underpinned by 20 years of research". This is the answer when scale and scheme coverage are the constraint OnSecurity cannot solve.

Published pricing: not published. Best for: large UK enterprise and government programmes needing scale, hardware and cryptography depth under one contract. Source: nccgroup.com

3. Pen Test Partners

Buckingham, with a New York office. Pen Test Partners LLP was incorporated on 18 March 2010 and its CREST Marketplace listing shows 16 years of membership and seven accreditations including Threat Led Penetration Testing and TLPT-FS, alongside NCSC CHECK, global PCI DSS QSA, UK CAA ASSURE, and Bank of England CBEST and STAR-FS partner assurance. The firm specialises "in areas such as maritime, aviation, and automotive security", having "tested everything from ships and planes to cars and EV chargers". Its PTaaS is a change-testing add-on: "billed in half day blocks", with anything likely to take "3 or more days" routed back to a conventional engagement.

Published pricing: not published. Best for: aviation, maritime, automotive, OT and physical security scopes, and anything needing CHECK, CBEST, STAR-FS or CAA ASSURE. Source: pentestpartners.com

4. Cobalt

San Francisco, US, with a CREST Penetration Testing accreditation in the Europe region. PTaaS across web, API, network, cloud and AI targets plus secure code review, delivered by the Cobalt Core, a community of vetted testers matched to your stack by the platform. Engagements start within 3, 2 or 1 business days across the Standard, Premium and Enterprise tiers. Cobalt's pricing page states that "A Cobalt Credit is the equivalent of 8 traditional pentesting hours", sold in annual packages, and that "Credits do not roll over into the next contract." Its retest term is the strongest published anywhere on this list: "Our PTaaS model provides unlimited on-demand retesting throughout your contract term."

Published pricing: not published. As of 5 September 2026 the pricing page carries no dollar figure, only credits and tiers. Best for: teams running many small tests a year who want a marketplace of matched testers and uncapped retesting. Source: cobalt.io/platform/pricing

5. WorkNest Secure

Chester, UK. Pentest People and Bulletproof now trade here: pentestpeople.com issues a 301 redirect to worknest.com/secure/pentest-people-bulletproof, and the page states that "WorkNest Secure combines the specialist expertise of Pentest People and Bulletproof in the UK, and Target Defense in the US, into one integrated cyber security partner." Published figures are "100+ accredited cyber professionals", "3,000+ customers supported", "24/7 security monitoring & response" and "11+ years CREST member". Delivery covers CHECK penetration testing, application security, network infrastructure, cloud and container testing, PSN IT Health Check, LLM security assessment, red and purple teaming, threat-led penetration testing and continuous scanning, surfaced through the GuardNest platform.

Published pricing: not published. Best for: UK mid-market buyers who want a platform-delivered test plus CHECK accreditation, managed detection and compliance support from one group. Source: worknest.com/secure

6. LRQA Nettitude

The cyber security practice of the LRQA assurance group. Its penetration testing page states "We are proud to be the only organisation in the world with a full suite of CREST accreditations", alongside accreditations "from CREST, the PCI SSC, ISC2, BCI, Chartered Institute of IT, and NCSC CHECK". It publishes that its experts "detected over 15,500 vulnerabilities through penetration testing during 2023", that it operates "in over 55 countries, with more than 250 dedicated cyber security specialists", and that it won the TEISS Award for Best Penetration Testing Service in 2024, with a published seven-phase methodology from scoping to reporting and debrief.

Published pricing: not published. Best for: UK financial services and multinational programmes where regulator-facing assurance is the requirement. Source: lrqa.com

7. Prism Infosec

Cheltenham and Liverpool. Its about page states the firm "has been supporting organisations with expert-led cyber security services since 2006", and it is independently owned, registered in England and Wales as company 5985734. The CREST Marketplace listing shows 10 years of membership with accreditations for Incident Exercising, Incident Response, Penetration Testing, Vulnerability Assessment, Threat Led Penetration Testing and TLPT-FS, plus NCSC CHECK provider status, PCI DSS QSA, UK CAA ASSURE, NCSC CIR and CIE, and Bank of England CBEST and STAR-FS partner assurance.

Published pricing: not published. Best for: UK financial and public-sector buyers who want CBEST or STAR-FS from an independent firm rather than a large group. Source: prisminfosec.com

8. Intruder

London, UK. Its about page states that "Intruder was founded in 2015 to help solve the information overload crisis in vulnerability management", that it was selected for GCHQ's Cyber Accelerator and named on Deloitte's Tech Fast 50 2023 list as the fastest-growing cybersecurity company in the UK, and that it now has "over 3,000 happy customers". The homepage describes "A single platform for AI pentesting, attack surface monitoring, cloud security and vulnerability management. Built for lean security and IT teams." That is the closest structural match to the scanning half of an OnSecurity subscription, with an on-demand test attached and an actual published figure.

Published pricing: AI-powered web application pentests "Starting from $3,500 / test" on the pricing page. Platform tier prices are not shown. Best for: lean teams that want continuous external scanning with an on-demand test attached, at a published starting price. Source: intruder.io/pricing

How It Compares: OnSecurity Side by Side

OnSecurity is compared here rather than ranked, because the post is about alternatives to it and a self-referential rank would be meaningless. Every cell below was read from the linked page on 5 September 2026.

Where OnSecurity Is the Better Choice

Honest answer, and it is a genuinely good product.

Hourly billing removes the worst part of pentest procurement. Day-rate rounding is where small scopes get overpriced across this whole industry. Quoting to the nearest hour, with the same rate for everybody, is a straightforwardly better deal for a team buying a two-and-a-half-day test.

The retest and cancellation terms are unusually buyer-friendly. Free retesting inside a window and no fee to cancel or reschedule remove two of the three things that make a testing contract feel risky to sign.

Scanning and testing on one invoice. Continuous external scanning, threat intelligence and scheduled tests under one monthly payment, with per-target control over which scanning features run and the ability to exclude noisy subdomains. Most buyers assemble that from two vendors.

You can talk to your tester. In-platform chat or Slack during the test, with findings reported live rather than held for a written report. For a small engineering team, that is worth more than a thicker PDF.

If your constraint is instead a scheme like CHECK, CBEST or STAR-FS, a price you can approve without a scoping conversation, source review inside the engagement, or fixes that arrive as pull requests, the firms above are built for that.

Buyer Checklist

Run these against every quote, including OnSecurity's. Ask for written answers.

1. Is a scheme written into your requirement? CHECK, CBEST, STAR-FS and CAA ASSURE narrow the UK field before anything else does.

2. Is the price published, quoted, or bundled into a subscription? Three different budget conversations, and "transparent billing" is not the same as a list price.

3. What is the billing unit? Hours, days, credits or a scoped engagement. Convert every quote to the same unit before you compare.

4. Is the retest window defined in writing? "Free within the window" needs the window in the contract.

5. Is source code in scope? Black-box only, or dynamic testing plus white-box review.

6. What does the AI actually do? Triage and deduplication, or exploitation and chaining. Our AI pentesting tools comparison sets out how to tell.

7. How do fixes reach engineering? A portal finding, or a pull request with a patch and a gate on the next merge.

8. How large is the technical bench? Ask for concurrent-engagement capacity against your audit date, not headline headcount.

9. Is the firm accredited, or are individuals certified? Different claims. Read our guide to verifying CREST accreditation.

Run your scope through the penetration testing cost calculator before you collect quotes, so you can tell an outlier from a scoping difference.

Frequently Asked Questions

What are the best OnSecurity alternatives in 2026?

The eight strongest alternatives are Stingrai, NCC Group, Pen Test Partners, Cobalt, WorkNest Secure, LRQA Nettitude, Prism Infosec and Intruder. Stingrai is a CREST-accredited penetration testing service provider at firm level, founded in 2021 in Toronto with a London office, fielding two named penetration testers per engagement who hold OSCE³, OSWE, OSEP, CREST CRT and CISSP, with 18 published CVEs and Halls of Fame at Apple, Google, the US Department of Defense and the US Federal Reserve. It sells a scoped engagement at a published price rather than hours: authenticated web and API testing across every user role for broken authorisation, IDOR and business logic, with Snipe reading application source and opening AutoFix pull requests, plus mobile, cloud, network, Active Directory, social engineering and red team scopes quoted separately, delivered one-time or continuously through a PTaaS portal with retesting and an attestation letter included. NCC Group and Pen Test Partners are the picks where NCSC CHECK or threat-led accreditation is the gate, and Intruder is the closest match to the continuous scanning half of an OnSecurity subscription.

How much does OnSecurity cost?

OnSecurity does not publish a rate card. Its pricing page explains the billing model rather than the price: "Our transparent, hourly billing means that everybody pays the same rate, and we quote to the nearest hour, not the nearest day", with an instant quote tool that generates "an estimated quote in just a few clicks" from a handful of scoping questions. For published comparison points, Stingrai lists US$3,000 per Autonomous assessment and US$6,800 for Hybrid, each covering one web application and associated APIs, and Intruder lists AI pentesting "Starting from $3,500 / test".

Is OnSecurity CREST-accredited?

Yes, for penetration testing. Its CREST Marketplace listing shows 8 years of membership with a Penetration Testing accreditation, plus the CREST AI Charter and ISO 27001 as company certifications, covering the United Kingdom and Europe. The listing does not show NCSC CHECK provider status, Threat Led Penetration Testing accreditation, or Bank of England CBEST or STAR-FS partner assurance, so scope any public-sector or regulated-finance requirement against a supplier that holds those schemes.

Does OnSecurity include free retesting?

Yes, within a defined window. OnSecurity states that it "will retest any findings you've fixed for free as long as it falls within the free retesting window", and separately that it charges no fee to cancel or reschedule a test. Ask for the window length in writing at contract time, because remediation cycles frequently run longer than a retest window. Among the alternatives, Cobalt commits to "unlimited on-demand retesting throughout your contract term" and Stingrai includes retesting in both published tiers.

How big is the OnSecurity team?

Its CREST Marketplace listing records 50 to 99 employees with 11 to 25 technical staff, and states that the company focuses entirely on security testing. That matches its published "manual-first testing" position and its stated investment in a structured internal training programme. It is also a real capacity consideration if you need multiple concurrent engagements across a large estate against a fixed date.

Which OnSecurity alternative publishes a fixed price?

Two. Stingrai publishes US$3,000 per Autonomous assessment and US$6,800 for Hybrid, each covering exactly one web application and associated APIs, with monthly equivalents of US$650 and US$1,275 on a 12-month engagement. Intruder publishes AI-powered web application pentests "Starting from $3,500 / test". NCC Group, Pen Test Partners, Cobalt, WorkNest Secure, LRQA Nettitude and Prism Infosec all quote every engagement.

Which alternative is best for a UK public-sector scope?

NCSC CHECK is the gate, and OnSecurity does not hold it. NCC Group, Pen Test Partners, LRQA Nettitude, Prism Infosec and WorkNest Secure all publish CHECK provider status. Prism Infosec pairs CHECK with CBEST and STAR-FS partner assurance from an independent Cheltenham base, while NCC Group brings the scale and procurement machinery large departments expect. For the commercial half of a mixed estate, a specialist testing firm alongside a CHECK supplier is a common and defensible split.

What is the difference between an AI-augmented pentest and an autonomous pentest?

The question is what the AI is allowed to do. AI-augmented testing, which is how OnSecurity describes its model, uses automation to reduce manual effort while human testers drive the engagement. An autonomous agent runs the attack chain itself: Stingrai's Snipe performs black-box dynamic testing and white-box source review, hunts IDOR, business logic flaws and broken authorization, and opens AutoFix pull requests, with certified penetration testers working the same engagement concurrently rather than reviewing afterwards. Ask any vendor which specific steps the AI performs and which a person performs, and read our AI pentesting tools comparison before you accept a general AI claim.

Which alternative is best for compliance evidence?

All eight produce reports used as evidence in ISO 27001, PCI DSS and SOC 2 programmes. LRQA Nettitude and NCC Group are the strongest fits where a regulator or a UK scheme is written into the requirement, and WorkNest Secure covers CHECK plus compliance support in one group. Stingrai's penetration testing supports SOC 2, ISO 27001, HIPAA, PCI DSS 4.0, NIST SP 800-53 and 800-171, DORA and NIS2 programmes, whether you buy a single annual engagement or a continuous program. Ask every vendor for a redacted sample report and confirm retest evidence is included, using our guide to the pentest evidence auditors accept.

Related Reading

• Top Penetration Testing Companies in the UK 2026

• Penetration Testing Companies in London 2026

• Intruder Alternatives 2026

• Continuous Penetration Testing vs PTaaS

• CREST-Accredited Penetration Testing Companies 2026

• The State of Penetration Testing 2026

• Best Vumetric Alternatives (2026): Canadian and US Penetration Testing Firms Compared

• TLPT Demand vs Supply in 2026: Mandated Entities, Accredited Providers, and the Coming Capacity Crunch

• Best BreachLock Alternatives (2026): PTaaS Platforms Compared on Testers, Evidence and Pricing

The Bottom Line

OnSecurity has built the cleanest commercial model in UK penetration testing. Hourly billing at a uniform rate, free retesting, no cancellation fee, live reporting and direct access to your tester solve real problems that most of the industry has been happy to leave unsolved.

Buyers keep comparing because the accreditation set stops at one CREST discipline with no CHECK, CBEST or STAR-FS, the technical bench is listed at 11 to 25 people, no rate card appears anywhere on the public site, and fix automation is not part of the platform. For business logic and authorization depth at a published price, with source review inside the engagement, the patch proposed in the pull request and a guarantee on the Autonomous tier, Stingrai is the closest like-for-like alternative and delivers UK work from a London office. Compare packages on the Stingrai pricing page, book a free scoping call, or send your scope through the Get a Quote form.