Company lists · Data verified August 2026

Top 25 Application security testing companies based in London, United Kingdom

Name: Application security testing companies based in London, United Kingdom
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Verified Aug 28, 2026 123 companies tracked

There are 123 application security testing companies headquartered in London, United Kingdom (RevenueBase, August 2026). RevenueBase tracks 2,053 professional contacts across them, including 204 with verified work emails and 235 with mobile numbers. London is the largest hub.

This list covers application security testing companies headquartered in London, United Kingdom, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Data current as of August 28, 2026.

123Companies

2,053Contacts tracked

204Verified emails

235Mobile numbers

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The 25 largest application security testing companies based in London, United Kingdom

Ranked by team size

Top 25 of 123 application security testing companies based in London, United Kingdom, ranked by team size, largest first. Data verified Aug 28, 2026. Click a count to unlock that company's people.
#	Company	HQ	Employees	Contacts	Verified emails
1	Covertswarm	London	51-200	65	41
2	Riversafe	London	11-50	55	1
3	Notsosecure Training Part Of Claranet Cyber Security	London	1,001-5,000	33	26
4	Equixly	London	11-50	28	21
5	Ssl247 A Sectigo Company	London	51-200	24	1
6	Toro Solutions	London	11-50	23	17
7	Audacix Makers Of Cyber Chief & Qsome	London	11-50	20	3
8	Secure Purple	London	11-50	20	2
9	th4ts3cur1ty.company	London	11-50	19	13
10	SE Labs	London	11-50	19	11
11	CST Limited Computer Security Technology	London	11-50	17	2
12	Eh1-Infotech Cybersecurity	London	11-50	15	1
13	Vulnhero	London	1-10	15	1
14	Datasixth Consulting	London	51-200	14	7
15	Laburity	London	1-10	14	4
16	CYTAL	London	11-50	11	10
17	Secureteam LTD	London	11-50	10	5
18	Pentiq	London	1-10	10	5
19	Appsecco	London	1-10	6	4
20	Remediata	London	1-10	4	2
21	Laneden LTD	London	1-10	4	2
22	Fortbridge	London	1-10	4	2
23	Cybersanctus	London	11-50	4	1
24	Illume	London	1-10	3	2
25	Heretek	London	1-10	3	2

Showing 25 of 123 application security testing companies based in London, United Kingdom

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Application security testing companies based in London, United Kingdom at a glance

As of Aug 28, 2026

1-10Median size (employees)

LondonLargest hub · 123 HQs

235Contacts with mobile numbers

1Emails re-verified in last 30 days

Companies by employee count

1-10

11-50

51-200

201-500

501-1,000

1,001-5,000

Application security testing companies by metro in the United Kingdom

Metro	Companies
Application security testing companies in London	123
Application security testing companies in Manchester	16
Application security testing companies in Birmingham	9
Application security testing companies in Cheltenham	7
Application security testing companies in Leeds	6
Application security testing companies in Cambridge	4
Application security testing companies in Milton Keynes	4

How this list was built

Source: The RevenueBase company graph: 21.3 million companies and 398.9 million professional contacts resolved from primary sources.
Inclusion: Companies whose own business descriptions match “application security testing companies”, with match quality audited by blind human judging, and headquartered in London, United Kingdom.
Ranking: Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
Verification: Contact records re-verify on a rolling cadence; 1 contacts on this list were re-verified in the last 30 days.
Refresh: Lists are refreshed periodically as the underlying company graph is re-verified. Last verified Aug 28, 2026.

Frequently asked

How many application security testing companies are there based in London, United Kingdom?

There are 123 application security testing companies headquartered in London, United Kingdom as of August 2026 (RevenueBase).

What is the largest company on this list?

Covertswarm, headquartered in London, tops this list with the largest team on record.

Which city has the most application security testing companies?

London leads with 123 headquartered companies, followed by Manchester (16) and Birmingham (9).

How do I get contact information for these companies?

A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 204 verified decision-maker contacts tracked across these 123 companies.

How current is this list?

The list is refreshed periodically as the underlying company graph is re-verified. It was last verified on August 28, 2026.

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About this data

RevenueBase is a B2B contact data platform. Its company graph covers 21.3 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph, the same data that powers RevenueBase's B2B data products and the free research portal.