Company lists · Data refreshed September 2026

Top 25 Online advertising agencies based in London, United Kingdom

Name: Online advertising agencies based in London, United Kingdom
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 5, 2026 2,404 companies tracked

RevenueBase identified 2,404 online advertising agencies headquartered in London, United Kingdom as of September 2026 and tracks 18,802 professional contacts across them, including 2,308 with verified work emails. Across the United Kingdom, London is the largest hub for this category.

This list covers online advertising agencies headquartered in London, United Kingdom, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed September 5, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.

How to read this list HQ checked on every row RevenueBase Smart Search rating on every row Refreshed Sep 5, 2026 86% judged on-target in blind review

2,404Companies

18,802Contacts tracked

2,308Verified emails

Explore this list → Free signup · no credit card · 500 free credits

The 25 largest online advertising agencies based in London, United Kingdom

Ranked by team size

Top 25 of 2,404 online advertising agencies based in London, United Kingdom, ranked by team size, largest first. Data refreshed Sep 5, 2026. RevenueBase Smart Search rates how each company's information relates to online advertising agencies: strong evidence (its own description names it), partial (names part of it), indirect (matched on the rest of its profile rather than the description shown). Click a contact count to view that company's people.
#	Company	RevenueBase Smart Search	Headquarters	Employees	Contacts
1	M C Saatchi Performance	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	201-500	457 contacts →
	Indirect evidence “We are a Global digital media agency specializing in taking a human approach to connecting brands with people across all channels.” Source: RevenueBase Database · checked Sep 5, 2026
2	BIG Group	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	177 contacts →
	Indirect evidence “Founded in 1991, with offices in Amsterdam, Bath, Dubai and London our award-winning employee-owned company has consistently ranked as one of the UK's leading independent digital…” Source: RevenueBase Database · checked Sep 5, 2026
3	Investis Digital	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	501-1,000	158 contacts →
	Indirect evidence “IDX (formerly Investis Digital) specializes in elevating companies and brands and maximizing technology to build strong, relatable, and authentic connections with their audiences.” Source: RevenueBase Database · checked Sep 5, 2026
4	E Intelligence	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	117 contacts →
	Indirect evidence “e intelligence is a renowned global leader in the digital marketing space.” Source: RevenueBase Database · checked Sep 5, 2026
5	FOUND	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	104 contacts →
	Indirect evidence “We're Found, the Everysearch™ agency.” Source: RevenueBase Database · checked Sep 5, 2026
6	Finixio	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	96 contacts →
	Indirect evidence “Finixio is UK based remote first Marketing & SEO Agency helping clients all over the world.” Source: RevenueBase Database · checked Sep 5, 2026
7	The Media People	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	83 contacts →
	Indirect evidence “Powered by our people, our campaigns put your audience first.” Source: RevenueBase Database · checked Sep 5, 2026
8	Social Boost	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	79 contacts →
	Indirect evidence “Social Boost has helped to grow more than 25 million real Followers, created content for 100+ brands, and generated over 300k sales leads.” Source: RevenueBase Database · checked Sep 5, 2026
9	Mind Digital Group	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	76 contacts →
	Indirect evidence “Mind Digital Group is an independent digital company that is focused on servicing global clients and partner agencies.” Source: RevenueBase Database · checked Sep 5, 2026
10	GA Agency	Partial evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	70 contacts →
	Partial evidence “GA Agency is an award-winning digital marketing agency helping brands all over the world grow their business and revenue in the online space.” Source: RevenueBase Database · checked Sep 5, 2026
11	Clicksco	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	66 contacts →
	Indirect evidence “As a new chapter in our Digital Agency begins, we are also a fantastic place to work, with a reputation for discovering and nurturing some of the finest minds in the business…” Source: RevenueBase Database · checked Sep 5, 2026
12	Eureka Digital	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	65 contacts →
	Indirect evidence “Eureka Digital is a multi-award-winning digital marketing agency specializing in healthcare and pharmaceuticals.” Source: RevenueBase Database · checked Sep 5, 2026
13	77agency	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	64 contacts →
	Indirect evidence “We are an award-winning full-service digital agency, part of Jakala group with 1,800 employees across 16 countries around the world.” Source: RevenueBase Database · checked Sep 5, 2026
14	OCM Digital Media	Partial evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	54 contacts →
	Partial evidence “OCM is a leading adtech agency providing solutions to advertisers, advertising agencies and to web, mobile & video publishers.” Source: RevenueBase Database · checked Sep 5, 2026
15	Stellar Search	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	48 contacts →
	Indirect evidence “We're a strategic digital marketing agency specialising in Paid Search, SEO, Google Shopping, Amazon and Social.” Source: RevenueBase Database · checked Sep 5, 2026
16	Harvest Digital	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	48 contacts →
	Indirect evidence “We are a leading independent digital media agency.” Source: RevenueBase Database · checked Sep 5, 2026
17	Digitex Technologies	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	51-200	46 contacts →
	Indirect evidence “Bringing our 10+ years of experience and knowledge of digital marketing, Digitex Technologies has now become almost synonymous with SEO, social media marketing, website building…” Source: RevenueBase Database · checked Sep 5, 2026
18	BAMBU	Strong evidence	London, United KingdomHQ checked Sep 5, 2026	n/a	45 contacts →
	Strong evidence “Bambu is an online marketing and advertising agency based in London, working with startup and growth brands across the UK, Europe and North America, founded by two ex-WPP…” Source: RevenueBase Database · checked Sep 5, 2026
19	Beautiful Digital	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	44 contacts →
	Indirect evidence “Beautiful Digital is a full service digital marketing agency.” Source: RevenueBase Database · checked Sep 5, 2026
20	Propeller	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	44 contacts →
	Indirect evidence “We’re a digital agency delivering stand-out experiences that generate results.” Source: RevenueBase Database · checked Sep 5, 2026
21	Dianomi	Partial evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	40 contacts →
	Partial evidence “Dianomi™ is the leader in premium native advertising for the financial services, technology, corporate and lifestyle sectors.” Source: RevenueBase Database · checked Sep 5, 2026
22	Kinase	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	39 contacts →
	Indirect evidence “Kinase is a leading Digital Marketing Agency providing services to some of the UK’s top companies.” Source: RevenueBase Database · checked Sep 5, 2026
23	Distinctly	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	38 contacts →
	Indirect evidence “Distinctly is an independent digital marketing agency with a passion for SEO, paid media, digital PR and content.” Source: RevenueBase Database · checked Sep 5, 2026
24	Cynosure Designs	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	36 contacts →
	Indirect evidence “Cynosure Designs is a UK & UAE-based IT and marketing agency providing 360° digital solutions that are experience-driven and results-focused.” Source: RevenueBase Database · checked Sep 5, 2026
25	Haarty Hanks	Indirect evidence	London, United KingdomHQ checked Sep 5, 2026	11-50	35 contacts →
	Indirect evidence “Haarty Hanks is a digital marketing agency comprised of tech nerds, creative designers and innovative strategists that plan and execute exceptional brand communications and web…” Source: RevenueBase Database · checked Sep 5, 2026

RevenueBase Smart Search

RevenueBase Smart Search assesses information from a company’s LinkedIn profile, information supplied directly by the company, its website, and other publicly available sources. It uses that information to rate how closely the company relates to this list’s category: online advertising agencies. Every row carries its rating and the description the rating was read from, so each one can be checked rather than taken on trust.

Strong evidence: The company's own public description of its business names online advertising agencies.
Partial evidence: Its own public description names part of online advertising agencies, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name online advertising agencies. The match rests on the rest of the company's public profile rather than the one sentence quoted here, so this is the rating to check first.

RevenueBase Smart Search is how these lists are built: RevenueBase's data engine and AI assemble the companies that match a category defined in a user's own words, so a list can be about what companies actually do rather than about whichever industry code they were filed under.

Showing 25 of 2,404 online advertising agencies based in London, United Kingdom

See the full list, filter by size, metro and specialty, and get verified emails and direct dials for all 2,308 reachable decision-makers.

Free signup · no credit card

View the full list →

Online advertising agencies based in London, United Kingdom at a glance

As of Sep 5, 2026

12.3%Verified-email coverage

7.8Average contacts per company

1-10Median size (employees)

Sep 5, 2026Page data refreshed

Companies by employee count

1-10

1,624

11-50

646

51-200

108

201-500

501-1,000

1,001-5,000

5,001-10,000

10001+

Email recency for this list is measured across the whole United Kingdom list rather than for London, so it is reported there. Company counts and contact totals on this page are exact for London, over 2,404 companies.

How this list was built

Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among online advertising agencies, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.

Source: The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
What qualifies: Companies headquartered in London, United Kingdom whose own description of what they do matches “online advertising agencies”. Matching reads each company's description, not its industry code or its name.
RevenueBase Smart Search: RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names online advertising agencies), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
What we exclude: Companies whose own description does not clearly place them among online advertising agencies, and records with no verified work email. Companies headquartered outside London are excluded even when they keep an office there.
Match quality: In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
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: Every listed company carries at least one verified work email, 2,308 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
Refresh: This page's figures were pulled from the company graph on September 5, 2026. Lists refresh periodically as the graph is re-checked.
Corrections: Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.

Online advertising agencies by metro in the United Kingdom

Frequently asked

What is RevenueBase Smart Search?

RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names online advertising agencies, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.

How many online advertising agencies are there based in London, United Kingdom?

RevenueBase identified 2,404 online advertising agencies headquartered in London, United Kingdom as of September 2026, matched on each company's own description of what it does rather than its industry code.

What is the largest company on this list?

M C Saatchi Performance, headquartered in London, tops this list with the largest team on record.

Which city in the United Kingdom has the most online advertising agencies?

London leads the United Kingdom with 2,404 headquartered companies, followed by Manchester (310) and Birmingham (201).

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 2,308 verified decision-maker contacts tracked across these 2,404 companies.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 5, 2026.

Ready to reach these companies? Verified emails and direct dials for all 2,404 online advertising agencies based in London, United Kingdom. Start with a free account, no credit card.

Download this list →

Related lists

Online advertising agencies by geography

Browse the directory

About this data

RevenueBase is a B2B data infrastructure company. Its company graph covers 60 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 with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.