How Long Does It Take to
Build an App in the UK?
A simple MVP takes 8–12 weeks. A complex platform takes 6–12 months. Here's the honest breakdown — phase by phase — plus what causes most projects to run late.
March 2026 · 10 min read · by Mantar Tech
App development in the UK takes 8–12 weeks for a simple MVP, 16–30 weeks for a mid-complexity business app, and 6–12 months for a complex platform. The single biggest driver of delay isn't development — it's unclear scope and slow client approvals.
Cost estimates are for UK-based development teams in 2026. See the full cost guide →
What happens in each phase?
Every app project goes through these phases. The difference in total time is almost always driven by scope, not speed.
Discovery & Requirements — 1–3 weeks
Clarifying what you want to build, who uses it, and what success looks like. Includes a scope document, user stories, and technical architecture review. Skipping this phase is the #1 cause of expensive rework later.
What slows this down: unclear business goals, multiple stakeholders with conflicting priorities, no existing specification.
Design & UX — 2–6 weeks
Wireframes, user flows, and final UI design. For complex apps this phase is significant — it's much cheaper to change a wireframe than already-written code. Design should be approved before development begins.
What slows this down: design revisions, brand guidelines decisions, approval loops with multiple stakeholders.
Development — 4–30 weeks
The core build phase. Frontend, backend, APIs, database, integrations. Weekly or fortnightly review cycles are standard. Scope changes during this phase are expensive — each change re-queues work and shifts dependencies.
What slows this down: changing requirements, third-party API issues, slow response to developer questions.
QA & Testing — 2–6 weeks
Functional testing, browser/device compatibility, security checks, performance testing. Bug fixing and regression testing. This phase is often underestimated and rushed — rushing it means launching with problems.
What slows this down: bugs found late requiring reworks, scope additions, poor test coverage.
Launch & Deployment — 1–3 weeks
Setting up production servers, staging environments, domain configuration, SSL, monitoring. For mobile apps: App Store and Google Play submission. Review times: iOS 1–3 days, Android 1–7 days, sometimes longer for the first submission.
What slows this down: App Store rejections, missing developer accounts, last-minute scope additions.
Post-launch Support — ongoing
Bug fixes from real user feedback, performance monitoring, minor feature additions. Most production issues appear in the first 2–4 weeks after launch. Plan for at least one month of post-launch support before the project is "done".
What slows this down: underestimating real-world usage patterns, no monitoring setup.
What actually slows projects down
Scope creep
"Can we just add…" is the most expensive phrase in software development. Every addition mid-build has a multiplier effect. Agree scope in writing before starting.
Slow client feedback
Developers waiting a week for approval on a small UI decision costs the same as a week of development time. Schedule review cycles in advance, not on demand.
Third-party API issues
Payment gateways, mapping SDKs, government APIs and data providers regularly have undocumented quirks. Budget extra time for every external integration.
Late design changes
A brand refresh or UX change after development has started can require redoing weeks of work. Design must be final before code is written.
Regulatory requirements
Healthcare, fintech and legal apps often face GDPR, FCA, NHS or ICO requirements discovered late. Compliance review should happen in Phase 1, not after launch.
Good discovery prevents all of the above
A thorough two-week discovery phase at the start typically saves 4–8 weeks later. It's the single best investment in a software project.
Web app vs mobile app: which takes longer?
🌐 Web App Timeline
- Simple CRUD app6–10 weeks
- Business tool with auth12–20 weeks
- SaaS platform20–36 weeks
- Enterprise system6–12+ months
No app store review needed. Faster iteration post-launch. Hosting setup is simpler.
Web app vs mobile app →📱 Mobile App Timeline
- Simple cross-platform app8–14 weeks
- Feature-rich cross-platform app16–30 weeks
- Native iOS (Swift)14–28 weeks
- Native iOS + Android (separate)24–48 weeks
Allow extra 1–3 weeks for App Store/Google Play reviews. iOS vs Android: which first?
How to deliver faster without cutting corners
1. Scope ruthlessly
Every feature you cut from version 1 saves more time than it costs. Build the smallest version that proves your core value. Add everything else in version 2.
2. Front-load the decisions
A well-run discovery phase (1–2 weeks) where all key decisions are made is worth 4–8 weeks of mid-build disruption. Don't start development with unanswered questions.
3. Approve design before coding starts
Finish and sign off on UI designs before a single line of code is written. Mid-build design changes are the most expensive kind.
4. Block time for reviews
Schedule review sessions in advance. Tell your team when you'll be available. Same-day responses to developer questions can shave weeks off a project.
5. Use cross-platform for mobile
React Native or Flutter builds one codebase for both iOS and Android. This typically saves 30–40% of development time compared to building native apps for each platform.
6. Plan your app store accounts early
Apple Developer accounts require review and can take several days to activate. Set up your App Store Connect and Google Play Console accounts at the start of the project, not the end.
Common questions about app timelines
How long does it take to build an app in the UK?
A simple MVP takes 6–12 weeks. A mid-complexity business app takes 12–24 weeks. Complex platforms take 6–12 months. These are realistic UK market estimates for a full development cycle from kickoff to launch.
How long does it take to build a mobile app?
A cross-platform app (React Native or Flutter) with basic features takes 8–14 weeks. A feature-rich app with real-time features, payments and push notifications takes 16–30 weeks. Native iOS + Android built separately doubles the timeline.
Can you build an app in 4 weeks?
A very simple landing page or internal tool can be built in 4 weeks. A proper app with user accounts, a backend and real features cannot. Any agency promising a complex app in 4 weeks is either underscoping or overselling.
How long does an MVP take to build?
A well-scoped MVP takes 8–16 weeks. The key word is "well-scoped" — an MVP that tries to do too much is not an MVP. The fastest MVPs have fewer than 5 core features and one target user persona. Our MVP development guide has a full scope framework.
Why do app projects always take longer than expected?
The most common reasons: scope creep mid-build, slow client approvals, unexpected third-party API integration issues, late design changes, and underestimated QA time. Good discovery and clear scope agreement at the start prevent most of these.
How long does it take to get an app approved by the App Store?
Apple's App Store review typically takes 1–3 business days. Google Play takes 1–7 days. First-time submissions sometimes face additional review. Factor 1–2 extra weeks into your launch timeline for app store review and any required revisions.
Plan your project further
How Much Does App Development Cost in the UK?
Full cost breakdown with price tables for every app type. Simple apps to enterprise platforms.
Read guide →How to Build an MVP in the UK
Scope your MVP correctly. What to cut, what to keep, and how to get to market in 10–16 weeks.
Read guide →How to Choose an App Developer in the UK
Six-step vetting process, 10 interview questions and red flags to avoid.
Read guide →