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AdTech Companies in London: 100+ Active Firms (2026)
AdTech companies in London build software and data services for buying, measuring and optimising digital advertising across the capital’s media economy.
Buying centres split between campaign activation for advertisers and agencies, monetisation tooling for media owners, and measurement or attribution infrastructure used by marketing, revenue and analytics teams. The better-fit suppliers tend to sell B2B platforms, data infrastructure or managed technology services into mid-market and enterprise accounts, rather than small-business ad buying. Engagements are usually specialist: integration with customer data, media inventory, reporting workflows and agency processes matters as much as the licence fee. London also favours firms that can sell internationally from a capital-based commercial team, reflecting the cross-border nature of digital advertising budgets.
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London has 132 actively trading AdTech companies, making the capital a concentrated but not very broad cohort by software-sector standards. Reported headcount across the group totals 1,882 people, which points to a mix of lean specialist teams and a smaller set of more staffed commercial operators. Turnover is also uneven: 20 companies sit above £5M in turnover, while 22 were incorporated since 2022. That combination leaves the market tilted towards operating businesses with live customer relationships, but with a younger layer still proving repeatable sales and retention.
Privacy and consent obligations shape the sector because audience activation, measurement and attribution depend on user-level signals, publisher permissions and customer-side marketing systems. That makes auditability a commercial issue as well as a legal one: buyers need to understand how segments are built, how campaign performance is attributed, and where responsibility sits between advertisers, agencies and media owners. Market structure also matters. Managed-service revenue can blur the line between software supplier and agency partner, while media-owner monetisation products tend to face different procurement tests from advertiser-side activation tools.
Scale-up paths appear uneven. Firms with direct access to buyer workflows, publisher inventory or hard-to-replace measurement pipelines tend to have clearer retention arguments than tools positioned as interchangeable campaign optimisation layers. Procurement is likely to keep favouring suppliers that can explain privacy treatment, attribution logic and operational hand-off without relying on opaque claims. Consolidation also looks plausible where smaller specialists overlap with agency services or media-owner tooling. The early-commercial layer may still produce new entrants, but revenue durability appears to matter more than category breadth.
132
Active firms
2026
20
Above £5M
Revenue threshold
22
Since 2022
Recent incorporations
Key facts
About 15% of the trading cohort reports turnover above £5M (20 of 132 firms) — the rest sits below that revenue band.
16% of the cohort was incorporated since 2022 (22 firms), so a sizeable share is in its first few filing cycles.
London’s media economy puts advertising software, media data services and campaign measurement vendors close to agency and brand budgets.
Buying centres tend to split between ad-buying tools, measurement products and optimisation services, each with a different sales motion.
Operating models vary between platform-style revenue, services-heavy delivery and small teams booking sizeable software or media income.
Top London AdTech companies
Trajectory
4y · 2020–NowFinancial sub-scores
Computed from 4 filingsDevelops and operates an omnichannel demand‑side advertising platform that enables brands and agencies to plan, buy and measure digital advertising campaigns. Uses mobile app and location‑based data…
Serves B2B customers: brands, advertisers and media agencies managing omnichannel digital campaigns, especially marketing and media-buying teams focused on privacy-first audience activation and…
Financial Health
HealthyHealthy · Hiring · 8% CAGR over 4y
Location
TEADS LIMITED
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsOperates a digital advertising platform that delivers and manages campaigns across websites, mobile apps, and connected TV. Provides ad formats, creative production, audience data, and performance…
Serves B2B customers: brand advertisers and marketing teams, plus premium media owners, publishers and OEMs, across open-internet digital advertising channels.
Financial Health
StableStable · Hiring · 5% CAGR over 4y
Location
Trajectory
5y · 2019–NowFinancial sub-scores
Computed from 5 filingsOperates a digital advertising technology platform providing demand‑side and supply‑side tools, data management and identity resolution. Enables advertisers to run programmatic campaigns and helps…
Serves B2B advertisers, brands, agencies and media publishers seeking programmatic advertising reach, connected TV audiences, data-driven targeting and ad inventory monetisation across global digital…
Financial Health
DistressedDistressed · -21% CAGR over 6y
Location
Onetag Limited
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsProvides a programmatic advertising platform that curates and filters ad inventory for demand‑side platforms. Uses AI and contextual data to shape traffic, optimise bidding, and connect advertisers…
Serves B2B programmatic advertising buyers, including marketers, advertisers, agencies and DSP users, as well as digital publishers in the open internet ecosystem.
Financial Health
StrongStrong · Growing, Hiring · 82% CAGR over 4y
Location
The Trade Desk
Provides a demand-side platform for programmatic digital advertising, enabling marketers to buy and manage campaigns across channels including connected TV, mobile, display, audio and digital…
Serves B2B advertisers, brand and performance marketing teams, agencies and programmatic media buyers across channels including CTV, audio, mobile, display, native, video and digital out-of-home.
Location
QUANTCAST LIMITED
Trajectory
2y · 2023–NowFinancial sub-scores
Computed from 2 filingsProvides administrative, marketing, and research and development services to affiliated companies within a digital advertising group that operates a programmatic demand-side platform, using data and…
Serves performance marketing teams, advertisers and agencies across B2B and B2C sectors, including DTC, retail, ticketing, tourism, travel, gaming and finance brands.
Financial Health
StableStable · Profitable · 0% CAGR over 1y
Location
Provides a programmatic advertising supply‑side platform that enables publishers to sell digital ad inventory through real‑time auctions and private marketplaces. Offers ad exchange technology,…
Serves B2B digital advertising customers: online publishers, media owners, brands, agencies and marketers buying or selling programmatic open-web, CTV and omnichannel ad inventory.
Location
Trajectory
2y · 2023–NowFinancial sub-scores
Computed from 2 filingsDevelops and operates a demand-side platform for planning, buying and managing digital advertising campaigns across multiple channels. The software enables activation on DOOH, mobile, desktop, TV and…
Serves B2B marketing teams at brands and advertising or media agencies that run digital campaigns across multiple channels and screens.
Financial Health
HealthyHealthy · Hiring · 24% CAGR over 1y
Location
Operates a programmatic advertising exchange and supply-side platform that enables media owners, app developers, and streaming TV publishers to sell digital ad inventory, and allows marketers and…
Serves B2B customers in digital advertising, including media owners, publishers, streaming TV publishers, app developers, marketers, agencies, DSPs and ad tech partners globally.
Location
Trajectory
3y · 2023–NowFinancial sub-scores
Computed from 3 filingsOperates an omnichannel advertising technology platform that connects brands, agencies and publishers. Provides tools for programmatic advertising, audience data activation, mobile app and web…
Sells to B2B media buyers and sellers: brands, agencies, DSPs, publishers and platforms. Targets advertiser teams in brand, performance, CPG and shopper marketing, plus app publishers and…
Financial Health
HealthyHealthy · Hiring · 12% CAGR over 2y
Location
Operates a programmatic advertising supply‑side platform and ad exchange that enables digital publishers to sell advertising inventory and allows advertisers to buy targeted ad placements across web,…
Serves B2B buyers and sellers in programmatic advertising, including digital publishers, advertisers, agencies, brands and data partners seeking omnichannel ad inventory and audience targeting across…
Location
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsDevelops and operates a programmatic advertising platform used by brands, agencies, and publishers to create, manage, and distribute digital ad campaigns across channels including display and digital…
Sells to B2B customers including advertisers, brands, media agencies and publishers running programmatic digital campaigns, especially teams seeking omnichannel, cookie-free advertising across…
Financial Health
WeakWeak · -9% CAGR over 3y
Location
StackAdapt UK Limited
Trajectory
5y · 2022–NowFinancial sub-scores
Computed from 5 filingsProvides a programmatic advertising platform that enables agencies and brands to plan, buy, and optimise digital ad campaigns. Offers AI‑driven targeting, campaign management and analytics across…
Serves advertising agencies, brands and in-house digital marketing teams running programmatic campaigns, across sectors including B2B, political, retail, travel, healthcare, finance and regulated…
Financial Health
StrongStrong · Growing, Hiring · 52% CAGR over 4y
Location
Azerion UK Limited
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsDevelops and operates digital advertising technology platforms that connect advertisers with online publishers. Provides demand‑side and supply‑side platforms, ad formats, audience data tools, and…
Serves B2B customers: brands and advertising agencies seeking omnichannel digital advertising, plus digital publishers and game/media owners monetising inventory, across Europe and global markets.
Financial Health
StrongStrong · Hiring · 22% CAGR over 4y
Location
ILLUMA TECHNOLOGY LTD
Trajectory
5y · 2020–NowFinancial sub-scores
Computed from 5 filingsDevelops contextual AI technology for digital advertising. Provides tools that classify and analyse online content and bidstream signals to enable cookie‑free ad targeting, campaign optimisation, and…
Serves enterprise brands, media agencies, broadcasters, publishers, online platforms and adtech partners involved in digital, programmatic and CTV advertising.
Financial Health
HealthyHealthy · -54% CAGR over 5y
Location
Develops AI-driven advertising technology that analyses live online intent signals to build audience segments and deliver targeted digital advertising campaigns. Its platform provides ID-free…
Serves B2B advertisers, brands, agencies and programmatic media teams seeking privacy-first digital targeting. Targets marketers running display, video and CTV campaigns across multiple markets,…
Financial Health
Insufficient historyInsufficient history
Location
VERVE MARKETING LONDON LTD
Trajectory
3y · 2023–NowFinancial sub-scores
Computed from 3 filingsDevelops advertising technology that connects advertisers with publishers across mobile apps, connected TV and other digital channels. Provides AI‑driven tools for campaign targeting and measurement,…
Serves B2B digital advertising buyers and sellers worldwide, including brands, media agencies, CPG/shopper marketers, app marketers, publishers, mobile app developers, and DSPs.
Financial Health
StableStable · Hiring · 14% CAGR over 2y
Location
Trajectory
4y · 2022–NowFinancial sub-scores
Computed from 4 filingsProvides a data platform for digital marketers and advertisers to collect, connect and manage customer data, build and enrich audience segments, resolve identities across devices, and activate…
Serves B2B digital marketers, advertising agencies, brands, and media/data owners needing audience data, identity, targeting, data collaboration, and monetisation across adtech, CTV, social, and…
Financial Health
HealthyHealthy · 0% CAGR over 3y
Location
Trajectory
5y · 2020–NowFinancial sub-scores
Computed from 5 filingsProvides advertising monetization services for digital publishers, including display and video ad placements for websites and mobile apps. Offers programmatic demand access, campaign management, ad…
Serves B2B digital publishers operating websites, mobile apps, video, CTV or audio inventory, particularly content-safe sites with at least 100,000 monthly pageviews.
Financial Health
StrongStrong
Location
ONAUDIENCE LTD
Trajectory
3y · 2023–NowFinancial sub-scores
Computed from 3 filingsProvides audience data and data enrichment services for digital advertising and analytics. Processes data from billions of devices to build audience segments, enable targeted and cookieless…
Serves B2B customers including marketers, advertising agencies, publishers, adtech platforms, data partners and data science teams running digital campaigns or building audience data products across…
Financial Health
StableStable · 0% CAGR over 2y
Location
AMPLIFIED INTELLIGENCE TECHNOLOGIES UK LIMITED
Trajectory
3y · 2023–NowFinancial sub-scores
Computed from 3 filingsProvides software and data services that measure audience attention to advertising across media. Offers a platform for campaign planning, in‑flight performance insights, creative testing, and APIs…
Serves B2B advertisers, brand marketers, media agencies, media teams and advertising platforms involved in campaign planning, creative testing and media performance optimisation.
Financial Health
StrongStrong · Hiring · 58% CAGR over 2y
Location
CRIMTAN CEE LIMITED
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsDevelops programmatic advertising technology and provides digital marketing services, including audience targeting, dynamic creative optimisation, connected advertising, and campaign management…
Serves marketing and digital advertising teams at established consumer brands and agencies, including retail, travel, tourism and fashion advertisers seeking programmatic campaign partners across…
Financial Health
DistressedDistressed
Location
Trajectory
3y · 2023–NowFinancial sub-scores
Computed from 3 filingsProvides an AI-powered commerce media platform that helps brands and agencies manage and optimise retail media, search and social advertising. The software centralises marketing data, offers…
Serves B2B marketing teams at brands, including CPG and commerce advertisers, plus media agencies managing retail media, search and social campaigns across publishers and marketplaces.
Financial Health
HealthyHealthy · -6% CAGR over 2y
Location
Trajectory
5y · 2022–NowFinancial sub-scores
Computed from 5 filingsProvides video advertising technology for delivering and streaming video ads across the open web. Offers programmatic video ad formats, campaign delivery, media buying, and performance measurement…
Serves global brands, advertising and media agencies, and publishers running programmatic open-web video campaigns, targeting marketing and media buying teams with digital advertising budgets.
Financial Health
WeakWeak · -61% CAGR over 4y
Location
App Samurai Limited
Trajectory
3y · 2023–NowFinancial sub-scores
Computed from 3 filingsProvides advertising technology for mobile apps and games, including a demand-side platform for user acquisition and retargeting, OEM-based app discovery placements, and rewarded playtime…
Serves B2B mobile app and game publishers, app marketers, and brands seeking app growth, including teams focused on user acquisition, retargeting, engagement, and monetization.
Financial Health
HealthyHealthy · Hiring · 53% CAGR over 2y
Location
Develops digital advertising technology that uses survey-based zero‑party data to build audience personas for targeted campaigns. Provides ad targeting, audience insights, and monetisation tools for…
Serves B2B customers in digital advertising: brands and media agencies of all sizes, plus digital publishers seeking advertising demand, across global open-internet markets.
Location
Provides a data collaboration and identity platform that enables organisations to connect, manage and analyse customer data across cloud, media and advertising platforms. Supports audience targeting,…
Serves large enterprises and Fortune 500 companies, especially marketing, data, analytics, privacy, security and developer teams in media and advertising, retail, CPG, technology platforms, and…
Location
LIFTOFF MOBILE LTD.
Trajectory
2y · 2024–NowFinancial sub-scores
Computed from 2 filingsProvides a mobile advertising and app growth platform offering user acquisition, ad monetisation, programmatic ad exchange, and creative optimisation tools. Uses machine learning and analytics to…
Serves B2B customers in the mobile app ecosystem: app marketers, advertising agencies, demand-side platforms, publishers, and mobile game developers.
Financial Health
HealthyHealthy · -9% CAGR over 1y
Location
Radio Net Media Limited
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsOperates a programmatic audio advertising platform that connects advertisers with digital audio publishers. Provides ad placements such as pre‑roll and mid‑roll across podcasts, music streaming and…
Serves advertisers, brands and media agencies buying digital audio inventory, plus audio publishers such as radio stations, streaming services, podcast networks, audiobook platforms and mobile apps…
Financial Health
StrongStrong · Growing, Hiring · 26% CAGR over 4y
Location
LIVEDOOH LTD
Trajectory
3y · 2023–NowFinancial sub-scores
Computed from 3 filingsDevelops software platforms for digital out‑of‑home (DOOH) media owners to manage advertising inventory, bookings and campaign delivery. Provides programmatic and direct sales integrations, yield…
Serves B2B customers in out-of-home advertising, including digital media owners, retail media network operators and DOOH integrators, from international operators to challenger outdoor advertising…
Financial Health
StableStable · Hiring · 41% CAGR over 2y
Location
Develops software platforms for digital audio advertising, including dynamic ad insertion, campaign management, programmatic buying and selling, podcast monetisation, and audience measurement tools,…
Serves B2B customers in digital audio: publishers, podcasters, streaming audio platforms, advertisers, agencies and media buyers involved in podcast and streaming audio advertising.
Location
Trajectory
2y · 2024–NowFinancial sub-scores
Computed from 2 filingsDevelops programmatic in‑game advertising technology that inserts intrinsic ad placements into video games across mobile, PC and console platforms. Enables advertisers to deliver campaigns within…
Serves brand advertisers, media agencies, and game developers/publishers seeking to reach or monetise gaming audiences across mobile, PC, console, and metaverse environments.
Financial Health
StrongStrong · Hiring · 43% CAGR over 1y
Location
Trajectory
2y · 2024–NowFinancial sub-scores
Computed from 2 filingsProvides technology platforms for connected TV (CTV) distribution, advertising and monetisation. Offers tools for FAST channel distribution, contextual TV ad targeting, ad inventory monetisation, and…
Serves B2B customers in the connected TV ecosystem: advertisers, brands, agencies, streaming TV publishers, content owners, FAST channels and CTV platforms.
Financial Health
WeakWeak · -9% CAGR over 1y
Location
Trajectory
2y · 2024–NowFinancial sub-scores
Computed from 2 filingsProvides an advertising technology platform that enables advertisers and publishers to create, manage, and deliver digital and connected TV ads, run paid social campaigns, and measure reach,…
Serves B2B advertisers, publishers and ad-tech partners, including teams in automotive, CPG, media, financial services, gambling, pharma, retail, telecoms and travel.
Financial Health
DistressedDistressed · -50% CAGR over 1y
Location
MULTILOCAL MEDIA LTD
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsProvides audience curation services for programmatic digital advertising. Operates a platform that analyses publisher domains, apps and audience data to build curated marketplaces, match advertisers…
Serves B2B customers in digital advertising, primarily advertisers, media agencies, publishers and media owners managing programmatic campaigns across web, app and CTV inventory.
Financial Health
HealthyHealthy
Location
Trajectory
5y · 2020–NowFinancial sub-scores
Computed from 5 filingsProvides a demand-side platform for B2B digital advertising. Uses intent data, IP targeting, and account-based marketing to deliver programmatic display ads to specific companies and decision‑makers…
Serves B2B marketing and sales teams seeking to target business accounts, plus B2B and media agencies. Industry focus includes technology, software, manufacturing, automotive, healthcare, logistics…
Financial Health
StrongStrong
Location
AudienceProject UK Ltd
Trajectory
4y · 2023–NowFinancial sub-scores
Computed from 4 filingsProvides a SaaS audience measurement platform for advertisers, agencies and publishers to analyse advertising campaign performance across channels including web, social media, online video, connected…
Serves advertisers, media agencies and publishers that run or sell multichannel ad campaigns across web, social, video, CTV and TV, especially teams needing independent audience measurement and…
Financial Health
StrongStrong · Hiring · 36% CAGR over 3y
Location
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsProvides software for TV advertising sales and campaign management, enabling broadcasters and networks to plan, forecast and manage cross‑platform ad inventory, audience segments, proposals, booking…
Serves B2B sales-side TV advertising organisations, including TV platforms, broadcasters, networks and programmers, with additional stakeholders such as advertisers, agencies and inventory partners.
Financial Health
HealthyHealthy · -10% CAGR over 4y
Location
Trajectory
4y · 2022–NowFinancial sub-scores
Computed from 4 filingsProvides programmatic advertising technology and services including high‑impact display and video ad formats, creative production, campaign management, and attention measurement tools that help…
Serves B2B customers in digital advertising, including brands, media agencies and advertisers running programmatic campaigns, plus publishers seeking premium demand, audience attention insights and…
Financial Health
HealthyHealthy · Hiring · 39% CAGR over 3y
Location
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsDevelops advertising technology that enables media owners and publishers to create, manage and distribute digital ad creatives across screens. Platform automates ad production, tagging, trafficking…
Serves B2B media owners, publishers and retail/CTV inventory owners that sell digital advertising, especially ad operations and commercial teams managing direct and programmatic campaigns for brand…
Financial Health
WeakWeak
Location
FENESTRA HOLDINGS LTD
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsProvides AI-based software platform for digital advertising teams that collects and analyses impression-level campaign and transaction data, automates reporting and data consolidation, and optimises…
Sells to B2B advertisers, biddable media teams and paid media agencies managing multi-platform digital advertising campaigns, including marketing and digital data leaders seeking campaign performance…
Financial Health
StableStable · -3% CAGR over 4y
Location
Trajectory
3y · 2024–NowFinancial sub-scores
Computed from 3 filingsProvides an online advertising technology platform offering contextual native advertising. Enables publishers to monetise website traffic and allows advertisers to run targeted ad campaigns through…
Serves B2B digital publishers seeking monetisation and advertisers buying contextual native advertising, including sophisticated publishers, advertisers and larger companies globally.
Financial Health
WeakWeak · -18% CAGR over 2y
Location
ID Ward Ltd
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsDevelops an AI-driven marketing data platform that connects publishers and advertisers. Provides tools for audience targeting, customer discovery and incremental campaign measurement across web,…
Sells to businesses in digital advertising, specifically publishers seeking to monetise audiences and advertisers/marketing teams aiming to reach, analyse and measure incremental audiences across…
Financial Health
StableStable · Hiring · 27% CAGR over 4y
Location
VENATUS MEDIA LIMITED
Trajectory
4y · 2020–NowFinancial sub-scores
Computed from 4 filingsProvides an advertising technology platform for gaming and entertainment publishers and brands. Offers tools for website, app and browser game monetization, programmatic demand, header bidding, ad…
Serves gaming and entertainment publishers, plus global brands and advertisers in sectors such as FMCG and automotive seeking to reach core, casual and kids gaming audiences.
Financial Health
HealthyHealthy · -57% CAGR over 5y
Location
XR GLOBAL (UK) LIMITED
Trajectory
2y · 2023–NowFinancial sub-scores
Computed from 2 filingsProvides software platform and services for advertising operations including creative asset management, rights tracking, ad delivery across media channels, and payment processing for actors,…
Serves global brands, advertising agencies, marketers, and commercial or entertainment production teams involved in advertising campaigns, media delivery, talent payments, and rights management.
Financial Health
WeakWeak · -7% CAGR over 1y
Location
Synapse TV Limited
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsDevelops software platforms for delivering ad‑supported streaming television services, including FAST and AVOD channels. Provides server-side ad insertion, consent management, scheduling and playout…
Serves broadcasters, content owners and TV platform operators offering ad-supported streaming, catch-up or subscription services on free-to-air TV and mobile platforms.
Financial Health
StrongStrong · Hiring · 28% CAGR over 4y
Location
Trajectory
5y · 2020–NowFinancial sub-scores
Computed from 5 filingsProvides software for digital advertising creative automation, enabling brands, agencies, and media platforms to design, generate, manage, and deliver rich media, video, and catalog ads, with tools…
Sells to businesses in digital advertising, especially brand marketing leaders, media teams and creative teams, plus media owners and operators such as publishers and media platforms seeking to scale…
Financial Health
DistressedDistressed · -8% CAGR over 5y
Location
TELMAR EUROPE LIMITED
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsProvides marketing analytics and media planning software that analyses consumer, social and media research data to generate audience insights, segmentation and cross‑media campaign planning tools for…
Serves B2B marketing organisations: creative and media agencies, media sales teams, and consumer brands that need audience insight, research, strategy, and cross-media planning support.
Financial Health
WeakWeak · -71% CAGR over 4y
Location
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsDevelops software for creating and delivering data‑driven dynamic audio advertisements. Its platform generates multiple ad variations using audience and contextual data and distributes them across…
Sells to businesses, primarily large advertisers and audio marketing teams using streaming, podcast and radio platforms. Serves brands in sectors including energy, automotive, technology,…
Financial Health
StableStable · 0% CAGR over 4y
Location
Trajectory
5y · 2021–NowFinancial sub-scores
Computed from 5 filingsDevelops software for creating and delivering data‑driven dynamic audio advertising. Its platform generates and publishes multiple ad variants using audience and contextual data, distributing them…
Serves marketing teams and media buyers at large consumer brands and agencies, including Fortune 500 advertisers, across retail, finance, CPG, QSR, pharma, travel, automotive, tech, entertainment and…
Financial Health
DistressedDistressed · -12% CAGR over 4y
Location
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How London AdTech companies work and how to sell to them
What they do
Revenue usually comes from annual platform licences, usage-linked fees, managed-service retainers, or a margin on media and monetisation flows. Advertiser-side tools are often sold as activation, optimisation or reporting software, while media-owner products earn through yield management, inventory access or workflow automation. Measurement and attribution suppliers sit closer to data infrastructure, with value tied to integrations, audit trails and reporting confidence. Pricing is rarely purely self-serve; most engagements need onboarding, tagging, data mapping and some continuing account management.
Who they sell to
Buyers usually sit in marketing, media, commercial and analytics teams, with procurement, legal and information security pulled in once customer data, audience permissions or publisher integrations are involved. Typical sponsors include chief marketing officers, heads of performance media, agency trading leads, revenue operations teams, commercial directors and data leaders. Larger advertisers and media owners often buy through direct sales or formal procurement, while agencies may test tools on a client account before wider rollout. Sales cycles tend to be measured in months when integration, privacy review and reporting acceptance all need sign-off.
What they buy
Most London AdTech firms tend to spend on the plumbing that lets them process campaign, audience and revenue data reliably: cloud hosting, data warehousing, pipeline monitoring, API management, observability, security testing and privacy operations. Commercial teams also buy CRM, sales engagement, proposal management, billing, usage metering and revenue recognition tools, particularly where pricing mixes licences, services and media-linked fees. Specialist services can matter as much as software, including privacy counsel, technical implementation partners, accounting support, agency relations, performance marketing, public relations and recruitment for sales engineers, data engineers and customer success staff.
Why and how to sell to them
AdTech buyers tend to evaluate vendors when privacy rules, customer reporting demands or publisher-side integrations expose operational friction. Other triggers include a move from managed service to platform revenue, expansion from UK customers into international accounts, a senior commercial or technical hire, or a spike in agency and enterprise procurement work. Outbound messages land better when they name a workflow problem: reducing manual campaign reconciliation, shortening integration time, improving auditability, lowering infrastructure waste, or helping sales teams prove retention. Generic efficiency claims are less persuasive in a market used to attribution arguments.
How this list is built
Data sources
This list is built from UK Companies House filings, XBRL accounts data, and semantic analysis of each company's public website. Revenue and headcount figures come from the most recent filed accounts; where the company has not filed, values are estimated using a model trained on filed history and peer benchmarks and are labelled as estimates.
Classification
Rather than relying solely on SIC codes, Firmbase classifies each company semantically: the company's website is crawled, an AI model reads what the company actually sells, and the company is placed into the relevant industry and subsectors. SIC codes are used as one signal but not the only one. This means a company that registered under a generic SIC code but pivoted into (for example) fintech is correctly identified as fintech, not as its original SIC category.
Freshness
The underlying company data is refreshed from Companies House continuously; filings appear in the list within days of submission. The curated list ordering is regenerated when the underlying data moves meaningfully (company count changes by more than 5%, a new company enters the top-ranked segment, or the filed-revenue numbers for the top firms change). You can see the last-updated timestamp near the top of the page.
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