Company lists · Data verified August 2026

Top 25 Application security consulting firms based in the United Kingdom

Name: Application security consulting firms based in the United Kingdom
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Verified Aug 28, 2026 445 companies tracked

There are 445 application security consulting firms headquartered in the United Kingdom (RevenueBase, August 2026). RevenueBase tracks 3,767 professional contacts across them, including 1,026 with verified work emails and 286 with mobile numbers. London is the largest hub.

This list covers application security consulting firms headquartered in the 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.

445Companies

3,767Contacts tracked

1,026Verified emails

286Mobile numbers

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The 25 largest application security consulting firms based in the United Kingdom

Ranked by team size

Top 25 of 445 application security consulting firms based in the 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	Resillion	Glasgow	501-1,000	387	203
2	Cybersec Consulting	London	201-500	141	76
3	Appcheck LTD	Leeds	51-200	97	64
4	Saepio Information Security	High Wycombe	51-200	73	57
5	Intruder	London	51-200	61	35
6	Cyberlab	Lincoln	51-200	56	41
7	Riversafe	London	11-50	55	1
8	Coretech Security	Cheltenham	51-200	41	7
9	Secarma LTD	Manchester	11-50	34	23
10	Aristi	Birmingham	11-50	32	10
11	Redfox Cybersecurity	London	11-50	24	6
12	Ssl247 A Sectigo Company	London	51-200	24	1
13	NGS Next Generation Security	Leeds	11-50	22	11
14	th4ts3cur1ty.company	London	11-50	19	13
15	Halo I.S	Leeds	11-50	19	9
16	DEV Null Security	Edinburgh	11-50	17	10
17	Peoplactive	Lee On The Solent	51-200	15	3
18	Eh1-Infotech Cybersecurity	London	11-50	15	1
19	Everycloud AI & Data Security	London	11-50	14	9
20	Datasixth Consulting	London	51-200	14	7
21	Ruptura Infosecurity	Milton Keynes	11-50	12	7
22	Equilibrium Security	Birmingham	11-50	9	5
23	Stratia Cyber	London	11-50	9	3
24	CYTIX	Manchester	11-50	8	6
25	Complete Cyber	Didcot	11-50	8	5

Showing 25 of 445 application security consulting firms based in the United Kingdom

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Application security consulting firms based in the United Kingdom at a glance

As of Aug 28, 2026

1-10Median size (employees)

LondonLargest hub · 172 HQs

286Contacts with mobile numbers

4Emails re-verified in last 30 days

Companies by employee count

1-10

302

11-50

109

51-200

201-500

501-1,000

1,001-5,000

5,001-10,000

Application security consulting firms by metro

Metro	Companies
Application security consulting firms in London	172
Application security consulting firms in Manchester	19
Application security consulting firms in Birmingham	11
Application security consulting firms in Edinburgh	9
Application security consulting firms in Cheltenham	9
Application security consulting firms in Leeds	7
Application security consulting firms in Bristol	7

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 consulting firms”, with match quality audited by blind human judging, and headquartered in the 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; 4 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 consulting firms are there based in the United Kingdom?

There are 445 application security consulting firms headquartered in the United Kingdom as of August 2026 (RevenueBase).

What is the largest company on this list?

Resillion, headquartered in Glasgow, tops this list with the largest team on record.

Which city has the most application security consulting firms?

London leads with 172 headquartered companies, followed by Manchester (19) and Birmingham (11).

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 1,026 verified decision-maker contacts tracked across these 445 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.