THEY.dev

THEY.dev is a software development agency with two headquarters in London and Cracow, founded by a team of 25+ dedicated specialists and associates. They've shipped 60+ projects and report that over 3 years, most clients stay with them. The company positions itself as a consulting-led development partner rather than a code shop. Their stated operating principles center on transparency (access to all work from day one), honesty (proposing better/faster/cheaper alternatives when they spot them), efficiency (reusing templates, components, and in-house solutions to skip boilerplate), and client focus (prioritizing long-term success over short-term gain).

They describe their engagement style as "like having an internal tech team"—some clients treat them as extended technical staff, others make them fully responsible for the technology side. The agency explicitly names four foundational service categories: Design & Discovery (prototyping and research), Proof of Concept (validating uncharted ideas), MVP (core features to launch and validate), and Custom Software Development (production-scale applications). They also offer Support & Maintenance under their S&M umbrella.

Services and capabilities

Design & Discovery is pitched as a pre-development phase. The service bundles UI/UX design in Figma, audience research, user interviews, competition analysis, monetization model definition, and expert review by developers, UX specialists, and QA. They deliver a clickable prototype, research reports, user stories, and a detailed development estimation. The Foundations package (£1600 + VAT) includes design, audience research, internal consulting, and estimation. The Visionary package (£3000 + VAT) adds the prototype, competition analysis, monetization models, and user stories. Both are fixed-price offerings delivered in weekly cycles with constant feedback loops.

Proof of Concept targets early-stage validation when critical project details are uncertain or there are unresolved technical, legal, or methodological questions. They validate concepts through small-scale builds, test external service integrations against documentation, flag potential limitations, and mitigate risk by surfacing hidden roadblocks before full development. This sits between Design & Discovery and MVP for projects with unknowns.

Minimal Viable Product development focuses on delivering core features for a functional, production-ready product. They provide scope estimation, build only must-have features, enable live user testing and feedback collection, and map future development stages based on real usage patterns. Aimed at startups and businesses validating market fit before heavy investment.

Custom Software Development is their mainstay for clients with clear vision, designs, and detailed requirements. They assign a dedicated team of developers, designers, and testers. QA is built in—features are tested by their QA team before going live. They maintain separate test and production environments, run performance/quality/security testing, and deliver a scalable, production-ready app. Project scope varies widely: some run 1 year with 2 developers, others 5+ years with 13+ people and millions of daily users.

Across all services, they mention GDPR compliance as achievable on a project-by-project basis and offer legal partner support for terms and privacy policies. They provide two post-launch support models: maintenance bundled into ongoing development (with out-of-hours support negotiable), or standalone support & maintenance with agreed SLAs and monthly hour allocations.

Notable work

Localgiving (fundraising and grant management platform for 2,200+ UK charities) used Next.js, React, TypeScript, AWS, AI, and TrueLayer integration for Open Banking verification plus an AI grant-writing assistant. HelloHosty (AI property management for short-term rentals) consolidated Airbnb/Booking.com reservations and guest comms via a single tool built on React, Java, Spring, MySQL, Docker, AWS, Twilio, and Stripe. Parliamentary Research Service replaced fragmented search and workflows with a centralized document platform (React, TypeScript, OpenSearch, AWS). Enforcio turned manual KYC/AML into a digital workflow with smart assessment forms and automated risk scoring (React, TypeScript, Stripe, AWS).

Client testimonials name outcomes: Common Surface highlighted quick, efficient delivery via Slack, Jira, Miro. Pixable praised elegant solutions and direct programmer contact. An advertising agency client received a "user-friendly, visually appealing" e-commerce site with positive user feedback and noted THEY's professional guidance. Onboard (in beta) commended smooth partnership and best-practice advice. M01's CEO reported minimal bugs, daily communication, and quality delivery on time.

How they work

Engagement begins with a free initial workshop to understand project details and ask targeted questions. They then deliver an interactive estimation tool where clients customize the offer and see price impacts before committing. Work happens in weekly cycles with constant communication, meetings, and feedback incorporation. Deliverables depend on the service: Design & Discovery hands over designs, prototypes, research reports, user stories, and a development plan. Support & Maintenance operates under negotiated SLAs, with pricing available upon request; free estimations are standard, though fixed-price packages exist. They note that free estimates are more accurate with detailed project descriptions.

Team and credentials

25+ dedicated specialists and associates across London and Cracow. The source does not name founders, publish formal certifications (ISO, SOC 2), or list partner statuses with major cloud providers. They state they are regularly recognized on Clutch and other platforms as leaders, though no specific badge or review count is mentioned in the material provided. GDPR compliance support is available; English proficiency is implied by client communication (Slack, Jira, daily standups with UK-based clients).