Top 20 Big Tech Companies & Startups in London

London remains one of the most active and influential tech hubs in the world. Many of Europe’s leading startups and scaleups began here. From AI systems to fintech platforms, tech companies in London focus on real business problems and build products designed for global scale. The city now ranks second worldwide for startup performance, behind only Silicon Valley. It is the only European city in the global top 10. Despite Brexit and the pandemic, London’s tech ecosystem has continued to grow and attract long-term investment.

For many of these companies, rapid growth wouldn’t be possible without trusted IT outsourcing in the UK — a way to access expert developers, speed up delivery, and scale quickly without inflating internal teams.

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Want to see who drives London’s tech scene forward? Here are 20 tech companies in London worth your attention, ranging from early-stage to established, all making a real impact.

London – The unicorns’ cradle

London leads Europe in creating billion-dollar startups. By 2021, the city hosted roughly 18,000 active startups and produced 87 unicorns, outpacing the combined total of Berlin, Stockholm, and Paris (78 unicorns). Since then, London’s count has passed 100 – Startup Genome reports 103 unicorns based here, up from just 12 in 2014, alongside an 800 percent surge in venture investment over the past decade.

Many of these success stories were born in fintech. As a fintech company hub, London offers ideal conditions for startups to build scalable mobile apps, grow their client base, and expand internationally. The city also attracts companies focused on generative AI, corporate travel, and innovative solutions in health and finance. A growing number of founders from Switzerland, the United Kingdom, and beyond now choose London as their launchpad.

The city also concentrates the bulk of the UK’s unicorns. Of the 44 British unicorns recorded in 2024, 37 are based in London, accounting for 84 percent of the country’s billion-dollar startups. These include platforms focused on AI, mobile applications, digital health, and clean tech.

Even in a quieter year for new entries, London still produced notable unicorns. Hotel-pricing platform Lighthouse secured $370 million from KKR to cross the $1 billion mark. Women’s health app Flo Health raised $200 million and joined the unicorn ranks. Health-tech leader Cera, known for its home-based care model, also passed the billion-dollar valuation. Consumer electronics giants like Samsung continue to invest in the region’s deep tech and AI infrastructure.

London’s unicorn growth is no accident. Government funding, deep venture capital networks, and a strong base of universities fuel innovation. Many of these companies also work with external development partners to scale quickly, especially in building complex systems or launching advanced digital products.

In short, London remains the cradle of European tech success, building companies that launch from local roots and scale to global influence.

Tech startups in London worth mentioning

Fifteen years ago, venture capital, startup ventures, and the very idea of a tech entrepreneur were still unfamiliar to most in the UK. Today, that landscape is entirely different for small businesses. London has become a magnet for ambitious founders, experienced operators, and global investors, producing some of the most dynamic startups in Europe. 

Fintech startups in London

From digital banks to payment infrastructure and open banking platforms, London’s fintech startups continue to redefine how individuals and businesses manage money. Below are some of the most influential players shaping the next generation of financial services.

FirstHomeCoach

FirstHomeCoach is one of the leading fintech products in the UK, helping people navigate the complex journey to homeownership. Founded by Life Moments in 2018, the platform offers personalised guidance on saving, mortgages, legal steps, and moving. Available as a white-label solution, it’s trusted by major financial institutions like Virgin Money and Standard Life to support first-time buyers with clear, step-by-step planning.

Monzo

Monzo ranks high among IT companies in London with its mobile-first bank. Since 2015, it has delivered clear budgeting tools, fee-free spending abroad, and instant balance alerts. Today, Monzo serves 8 million retail users and 30,000 businesses. This software company in London powers a growing developer ecosystem through its open API.

GoCardless

As one of the most notable tech companies in London, GoCardless automates direct debit for subscription and invoice collection. Since 2011, this London-based IT company has processed over £30 billion in payments across 29 markets. Its predictive failure analytics and developer-friendly API attract SaaS providers and financial services firms.

Checkout.com

Checkout.com ranks among the biggest UK tech companies and handles payment workflows for enterprises such as Shopify and Coinbase. This global company in London provides software solutions for processing card, wallet, and bank transfer methods in 150+ currencies. Its real-time fraud detection and custom routing boost approval rates in line with SEO best practices.

Zopa

Zopa began as a peer-to-peer lender and evolved into a full digital bank. Today, this London startup offers savings, loans, and mobile current accounts. Zopa has processed £5 billion in consumer lending since 2005 and counts itself among the top tech companies in London.

HealthTech & biotech startups in London

The rise of technology companies in London spans far beyond fintech and AI. HealthTech and biotech firms now lead breakthroughs in diagnostics, eldercare, and digital health platforms.

Cera

Cera applies AI-driven triage and a network of 15,000 carers to deliver on-demand eldercare. This global company based in London uses predictive analytics to schedule visits and track outcomes. Cera proves that health tech startups in London can scale across six European markets while cutting care costs and improving patient experience.

Babylon Health

Babylon Health ranks among technology companies in London with its AI symptom checker and video consultations. Since 2013, it has completed over 30 million virtual visits. A $500 million IPO on the NYSE in 2021 valued the firm at nearly $4 billion. Babylon brings digital transformation to healthcare systems and reinforces London’s position among the largest tech companies worldwide.

Healx

Healx hunts drug candidates for rare diseases by applying machine learning to vast biomedical data. Since its inception, this tech startup in London uses algorithms that sift through journals, patents, and clinical records. A $63 million Series C in 2022 funds multiple Phase II trials. Healx showcases how artificial intelligence and data analytics from UK companies drive breakthroughs in the life sciences.

Thriva

Thriva mails home blood-test kits and links results to a secure dashboard for personalized insights. It processes samples in UK-accredited labs and delivers reports in 48 hours. A £40 million Series B in 2022 backed lab expansion and new panels. Thriva illustrates how London startups drive digital transformation in preventive care and chronic disease management.

Owlstone Medical

This solution detects disease markers in breath samples with its Vulcan platform. It applies machine learning to identify volatile compounds tied to cancer and inflammatory disorders. A $75 million Series D in 2023 will support large-scale clinical trials and global rollout. Owlstone joins the roster of tech companies in London, revolutionizing diagnostics.

AI & machine learning startups in London

London stands at the forefront of artificial intelligence and machine learning in Europe. Backed by a deep talent pool, strong academic research, and steady investment, the city has produced a new wave of startups focused on real-world applications of AI.

DeepMind

DeepMind leads the AI field with breakthroughs in reinforcement learning and protein folding (AlphaFold). Acquired by Google in 2014, it ranks among the biggest UK tech companies. DeepMind partners with NHS trusts to improve patient care and with energy firms to boost efficiency, showcasing artificial intelligence at scale.

Faculty AI

Faculty AI designs enterprise solutions that provide automation for data pipelines and data extraction model deployment. A $100 million Series C in 2021 fuels product enhancements in model governance and performance monitoring. Faculty AI stands out among AI chatbots and machine learning consultancies in London, driving measurable ROI for financial services and defense clients.

Signal AI

Signal AI processes 200 million sources daily to deliver real-time media intelligence. It applies natural-language processing and data analytics to track brand risks and market trends. An $80 million Series D in 2022 supports expansion into ESG and supply-chain analytics. Signal AI joins the ranks of software companies in London that serve over 1,000 enterprises.

Prowler.io

Prowler.io optimizes decision workflows in finance, logistics, and robotics using probabilistic models. Clients report efficiency gains up to 25 % in trading and supply-chain operations. A $40 million round in 2021 backs research in multi-agent systems and simulation. Prowler.io embodies the spirit of tech startups in London, applying machine learning to operational challenges.

Onfido

Onfido verifies identities with computer vision and biometric checks across 195 countries. It processes millions of onboarding requests for banks and gig-economy platforms. A $100 million funding round in 2021 made it one of the top tech companies in London. Onfido’s adaptive fraud filters and fast verification flow set standards in digital identity.

Cybersecurity startups in London

Supported by the UK’s robust regulatory environment and access to security expertise, these cybersecurity startups address threats across cloud platforms, enterprise networks, and human risk. 

Darktrace

Darktrace uses self-learning AI to detect threats across networks, cloud environments, and IoT devices. Since its 2021 IPO on the London Stock Exchange, the firm joined the club of big tech companies in London valued over £1 billion. Darktrace’s Autonomous Response safeguards over 5,000 customers against novel attacks.

Tessian

Tessian protects corporate email by spotting anomalies in communication patterns. It prevents data loss, phishing, and mis-sent messages before they reach inboxes. A $80 million Series D in 2022 fuels U.S. expansion. Tessian ranks among the leading IT companies in London for enterprise security.

CybSafe

CybSafe leverages behavioural science and cloud tools to improve security hygiene among staff. Its platform tracks user experience and delivers adaptive learning modules on phishing, password safety, and compliance. A £15 million Series A in 2021 financed the rollout across finance and healthcare firms. CybSafe stands out among London tech companies that address human risk.

PropTech & SaaS startups in London

London’s PropTech and SaaS startups are changing how property, operations, and business systems function at scale. These London based IT companies combine engineering excellence and market focus to offer reliable, scalable software to businesses and consumers.

Nested

Nested offers a hybrid estate-agent model that guarantees homeowners a cash offer within 48 hours and cashback on sale completion. Since 2016, the firm has processed over £2 billion in transactions. A £45 million Series B in 2021 supports expansion. Nested ranks among software companies in London that reshape property management with digital tools.

Goodlord

Goodlord automates rental agreements, payment collection, and compliance checks for lettings agents. Since 2014, it has managed 30,000 properties per month. A £33 million Series B in 2022 funds new features in tenant experience and integrations with landlord insurance. Goodlord exemplifies London-based IT companies that deliver management software for real estate workflows.

Each of these startups based in London uses advanced tech, shows real market progress, and attracts strong investment. Together, they reflect the strength and variety of the UK’s tech scene, which is currently valued at over $1.2 trillion.

The future of the tech space in the UK

The UK’s tech sector is entering a pivotal phase, marked by substantial innovation, strategic investment, and sustained growth. To help you stay ahead, Relevant Software experts have prepared key outlooks on what’s coming next — and how to get ready.

Government support and innovation

The government backs this growth with targeted funding and initiatives. One example is ARIA, an £800-million programme designed to support ambitious projects in areas like robotics and biology. Another initiative, the Regulatory Innovation Office, aims to simplify rules to speed up innovation, especially for emerging technologies such as AI and autonomous systems.

Focus on AI and cybersecurity

Artificial intelligence remains central to national policy. A multibillion-pound plan will scale up AI infrastructure by 2030, boosting computing power twentyfold. AI growth zones will emerge across former industrial areas, opening doors for AI-focused early-stage companies and scaleups alike. Meanwhile, the need for strong cybersecurity capabilities grows. The UK’s cybersecurity sector expects 10-12% annual growth, fueled by increased digital risk and demand for secure, scalable software.

Addressing the scale-up challenge

Despite its strengths, growing UK-based fintech startups and SaaS product development companies into global enterprises still pose challenges. Policymakers are addressing this by encouraging pension fund investment in domestic ventures. Many of these scaleups rely on outsourced product development in the UK to access world-class engineering teams and deliver complex integrations without growing internal teams.

Relevant Software clients illustrate this transformation clearly. We launched the FirstHomeCoach app, upgraded My Theory Test by James May, and helped Red Driving School significantly increase app revenue. Swift Onboard built custom onboarding software with our support, while Return2Play streamlined athlete health management by leveraging our custom software development in the UK.

Optimism among SMEs and tech leaders

Based on the Relevant Software experts’ survey, despite global economic uncertainties, UK tech remains optimistic. According to techUK, the UK continues to be an attractive place for starting and scaling technology businesses, due to its supportive operating environment and rich talent base.

Overall, with continued investment, strategic policy, and growing talent pools, the UK tech space is poised for sustained innovation, creating a thriving landscape for startups and scale-ups in the coming decade.

Final words

London rewards execution, not ideas alone. In one of the world’s most competitive tech ecosystems, speed, quality, and precision separate promising startups from industry leaders.

If your goal is to join the ranks of top tech companies in London, you need more than a concept — you need reliable software products built at the right time and aligned with your strategic goals. Relevant Software delivers this through expert engineering, domain expertise, and full-cycle support.

Our teams specialize in outsourced product development for the UK market, including data analytics, machine learning, and complex system integration. Whether you’re building for mobile phones, web platforms, or enterprise-scale deployments, we provide the senior talent and delivery capabilities you need without the long timelines of in-house hiring.

Your product deserves a team that builds with purpose. Let’s talk about how Relevant can help you move faster, launch stronger, and scale smarter. Contact us today to take the next step.

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