No signal, no app
Your users open the app underground, in a basement bar or in a lift. If the main screen needs a live connection to show anything at all, they close it.
Mobile app development · London
Mobile App Development in London
Consumer and B2B apps for London startups and businesses — hospitality, fitness, fintech, events and field teams — built for iOS and Android, designed for people using them one-handed on the move, and taken all the way through app store review.
- One codebase for iOS and Android, or native
- App store submission planned from the start
- Developer accounts in your name, not ours
The hard part
What London app users will not put up with.
People give an app one or two chances, usually on the move. These are the usual reasons it gets deleted.
What makes a London app stick
- The core journey works offline and syncs later
- Something useful happens in the first session
- Notifications people are glad to receive
- Features built around real places and journeys
One hand, one minute
People use apps on crowded platforms, on the bus and walking between meetings. Journeys that need two hands and half a dozen screens lose them.
Crowded categories
Food, fitness, social and money apps compete with well-funded names. A clear, narrow first version beats a cluttered copy of theirs.
Review surprises
A rejection over payments, sign-in or privacy wording can push back a launch planned around a press moment, an event or an investor update.
What we build
Apps we build for London businesses.
Consumer and B2B apps with a clear job to do — plus the backend, admin tools and integrations that keep them running.
Order, book and collect
Ordering, table booking, loyalty and click-and-collect apps for restaurant groups, cafés and bars, connected to the tills and kitchen screens already in use.
Classes, workouts and progress
Class booking for studios and gyms, workout and nutrition tracking, memberships and payments — with reminders people actually want.
Money apps people trust
Payments, wallets, savings and spending insights, with secure sign-in, clear consent screens and authorised providers handling the regulated parts.
Things to do, people to meet
Event discovery, meet-ups and community apps with chat, invitations and recommendations that make sense for where people are in the city.
Apps for people on the road
Inspections, deliveries, site visits and engineer rotas across the boroughs — offline-first, with photos, signatures and sync when the signal returns.
Apps that know the commute
Viewing schedules with travel times, visitor guides and itinerary apps that account for how people actually get around London.
Transport-aware apps
Building on TfL open data.
Transport for London publishes much of its live and reference data through the TfL Unified API: line status and disruptions, arrival predictions, journey planning, stops and stations, cycle hire docking points and road disruption. For a London app, it can turn a generic feature into a genuinely useful one.
A restaurant app that warns guests about a line closure before they set off. A property app that shows the commute from each flat to the office. An events app that suggests the least disrupted route home. A field-service app that plans visits around roadworks. None of these needs a huge build — they need the data used carefully.
Careful means a few practical things. Production use means registering for an API key, working within usage limits and following the open data terms, including attribution. Live data should be cached and refreshed sensibly rather than requested on every screen. Journey times are predictions, and the interface should present them that way. And when a feed is slow or unavailable, the app should degrade gracefully rather than freeze.
- Line status and arrivals with sensible caching
- Disruption alerts tied to a user’s saved journeys
- Attribution and terms of use handled properly
- A clear fallback when a live feed is slow or down
Cross-platform or native?
Choosing how to build your app.
A straight recommendation based on what the app needs to do — not on what we would most enjoy building.
Cross-platform
One React Native or Flutter codebase for iOS and Android: quicker to build and cheaper to maintain. Our usual recommendation for consumer and B2B apps, including ones with maps, payments and chat.
Flutter app development
Native Swift and Kotlin
When the app leans hard on the device — background location, Bluetooth, heavy camera work, widgets and watch apps — or when smoothness is the product itself.
Swift app development
A web app first
If people will only use it occasionally, a fast mobile web app may beat an app store listing. We will say so when that is the better first step.
Web development in London
How we work
How an app goes from idea to the stores.
Seven stages, with a build on your phone every fortnight — so feedback comes from using the app, not from reading about it.
- 01
Discovery
Who uses the app, where and when — on the Tube, behind a bar, on a site visit — and the one journey that has to feel effortless.
Users, moments of use and core journey
- 02
Strategy
We agree what to build first and what to leave out, pick the engagement model, and set milestones with a budget range in pounds.
Scoped first release and estimate
- 03
UX & architecture
A clickable prototype on real phones, tested with target users, plus the platform choice and the backend and API design behind it.
Tested prototype and platform decision
- 04
Development
Two-week sprints, each ending with a build on TestFlight and Google Play testing tracks and a demo on video.
An installable build every fortnight
- 05
Testing
Testing across iOS and Android devices, on poor and absent connections, with accessibility settings such as larger text, and through the unhappy paths: failed payments, expired sessions, denied permissions.
Device test report and release candidate
- 06
Launch
Store listings, privacy answers, submission and a phased release, with crash reporting and analytics switched on.
Live in the App Store and Google Play
- 07
Optimisation & support
Fixes, updates for each year’s new iOS and Android versions, and a roadmap driven by what users actually do.
Support retainer or handover
App store realities
Getting through app store review.
Apple and Google review every release, and most rejections are predictable — so they are designed out in the early sprints rather than found in launch week.
Accounts in your company’s name
Developer accounts on both stores belong to your organisation — never to us or a freelancer. Apple and Google each ask for a D-U-N-S number, so we start that early.
Payments the stores accept
Digital content and subscriptions usually have to use in-app purchase; physical goods, bookings and services can use Stripe. Getting this wrong is a common rejection.
Privacy answers that match the code
What you declare in the App Store privacy details and the Play Console data safety section must match what the app, and every SDK inside it, really collects. We audit third-party SDKs before those forms are filled in.
Previews for your stakeholders
TestFlight and Google Play testing tracks put each sprint’s build on your team’s and investors’ phones, not just the final release.
Review time in the plan
Review is usually quick but not predictable, so launches tied to a press date or an event get buffer built in.
Staged roll-outs
Phased releases and crash reporting, so a bad build reaches a small group of users rather than everyone at once.
Technology
The mobile stack we use.
Widely used tools with big communities, so hiring for your app later is straightforward and nothing is locked to us.
Cross-platform
React NativeFlutterExpoTypeScript
Native
SwiftKotlinWidgets and extensionsBackground location
Backend
Node.jsPythonFirebasePostgreSQL
Location and transport
TfL Unified APIMaps and geofencingOffline cachingPush notifications
Payments
StripeApple Pay and Google PayIn-app purchasesSubscriptions
Release and quality
TestFlightGoogle Play testing tracksCrash reportingCI builds
Engagement models
Ways to build your app with us.
Most apps start with a discovery sprint and move to a fixed-price build. Once the app is live, named developers keep the roadmap moving.
Discovery sprint
From £2,000 fixed fee
You have an idea or a problem, but not yet a scope you would trust a quote against.
- Workshops with your team
- Prototype or technical spike
- Written scope, plan and estimate
Fixed-scope project
Quoted after discovery
A defined build — an MVP, a rebuild or a feature set — with milestones and a fixed budget.
- Agreed milestones and deliverables
- Milestone-based billing
- A demo at the end of every sprint
Dedicated developers
From £2,900 per developer / month
Ongoing roadmap work where you want named engineers inside your own sprints.
- Named, senior engineers
- Work inside your tools and sprints
- Scale up or down as the roadmap changes
Prices are in GBP. Every estimate is confirmed in writing after a discovery call — the figures above are where engagements start, not a quote.
Relevant work
Products we have designed and built.
A money-transfer app, a fitness tracker and a social events app — three consumer mobile products from our case studies.
All case studiesFintech · Mobile
Sendora
Mobile-first money transfer and card app for a cross-border fintech.
React NativeNode.jsMapboxStripe
Read the case studyHealth & Fitness · Mobile
Workout Book
Fitness app for workouts, nutrition logging and progress tracking.
React NativeNode.jsFirebasePostgreSQL
Read the case studySocial · Mobile
Pademi
Social discovery app for events, meet-ups and friend introductions.
React NativeNode.jsSocket.ioPostgreSQL
Read the case studyWhy Techsleight
What working with us is actually like.
No inflated numbers — just how we run projects, and what you can hold us to.
Product engineering, not ticket-taking
We ask what the software is for before we estimate it — and we will tell you when something should not be built, or should be bought instead.
AI where it earns its place
LLM features, retrieval and automation built with evaluation, guardrails and cost controls, and plain software where that is the better answer.
Full-stack under one roof
Design, frontend, backend, mobile, cloud and QA in one team, so nothing falls between suppliers.
UK-focused delivery
UK business hours, estimates in pounds, and a contract with a UK company. Our engineers are based in the UK and India.
Flexible engagement
A fixed-scope project, dedicated developers or a monthly retainer — and you can move between them as the work changes.
You own everything
Code, IP, cloud accounts and documentation are yours from day one. We sign an NDA before discovery if you need one.
Support after launch
We stay on for fixes, upgrades and new features, or hand over cleanly to your in-house team with the documentation to match.
FAQs
Questions we get asked.
Straight answers on scope, cost, timelines and how we work. If yours is not here, ask us directly.
What does app development cost for a London business?
The main drivers are the number of journeys and screens, the backend, and integrations such as payments or live data. Discovery, from £2,000, turns the idea into a fixed quote for the build. Running costs — hosting, third-party APIs and the yearly OS updates — are separate; we forecast them before you commit.
Should we launch on iOS or Android first?
Usually neither: a React Native or Flutter app ships to both from one codebase. If budget forces a choice, we look at who your users are and which phones they carry, using your analytics or customer research rather than assumptions.
Can you use TfL data in our app?
Yes. TfL publishes open data through its Unified API — line status, arrival predictions, journey planning and more — under terms that include registration and attribution. We design caching and fallbacks so the feature stays useful when a feed is slow, and check the current terms for your use case.
Do you handle app store submission?
Yes, with you. We prepare builds, store listings, screenshots and privacy answers, submit through your developer accounts and deal with reviewer questions. The accounts stay in your company’s name, so you never depend on us to publish an update.
How does our team test the app while it is being built?
Each sprint’s build lands on your team’s phones via TestFlight or a Google Play test track, so feedback comes from real use on real devices, backed by a demo on video every fortnight.
Who will we deal with day to day?
Delivery is remote-first: you work directly with the engineers building your app and the person accountable for delivery, in a shared Slack or Teams channel on UK business hours, with a written update every week and a demo every fortnight. The contracting party is Krapton IT Consultancy, a UK company trading as Techsleight Labs.
Our app was built by a freelancer who has gone quiet. Can you help?
Often. First we recover access — developer accounts, signing keys, source code, backend hosting — because without them nobody can ship an update. Then we review the code, fix crashes and store issues, and advise whether to keep improving the app or rebuild it.
How do you make apps work with a poor signal?
By designing for it: the core screens load from data cached on the device, actions queue and sync when the connection returns, and the app says clearly what is waiting to send. We test on throttled and offline connections, not just office Wi-Fi.
Do you build apps that take payments?
Yes. Physical goods, bookings and services usually go through Stripe with Apple Pay and Google Pay; digital content and subscriptions often have to use in-app purchase under store rules. We check the current rules for your category before designing checkout, because they differ and they change.
What happens after launch?
Apple and Google release new operating system versions every year and SDKs get deprecated, so apps need regular attention. We offer support retainers covering fixes, updates and new features — or hand over to your own developers with documentation and access to everything.
Start a project
Have an app idea, or an app that needs fixing?
Describe the people using the app, the job it has to do and where they will be when they open it. Expect a reply within one working day, with our questions, a view on platform and a suggested first step.
What happens next
- 1A senior engineer reads your brief within one working day, and replies with questions or a first view.
- 2A 30-minute call to understand the goal, constraints and what good looks like — no sales script.
- 3A written proposal with scope, milestones, team and a GBP estimate you can take to your board.
Techsleight Labs is a trading name of Krapton IT Consultancy.
Explore