How to Build a Mobile App: A Step-by-Step Process for the Client

Building a mobile app is a sequence of seven stages — discovery, scope, design, development, testing, store release and maintenance — and at every one of them the studio is waiting on a decision or an asset from you. This guide covers how to build a mobile app from the client’s side of the table rather than the software house’s: what you hand over, who on your team approves it, and what artefact you get back. Most projects do not stall because the code is difficult. They stall because nobody approved the wireframes.

What the mobile app development process looks like step by step

The process has seven stages: discovery and goal, scope and requirements, UX/UI design, development in sprints, testing and sign-off, release to the stores, and maintenance. The table below shows that same process from where you sit — what each stage actually asks of you.

The stages overlap only partly: design of later screens can run alongside coding of earlier ones, but development cannot start without an approved scope. If you want to estimate how long it takes to build an app, count not only the team’s working days but also the approval rounds on your own side.

Discovery and goal: where to start when you have an app idea

Start by writing the business goal in a single sentence, before you describe a single feature. The studio needs to know which process inside your company is supposed to change and how you will recognise that it has. Features follow from that answer, not the other way round.

The most common mistake at the start is describing your app by comparison with somebody else’s product. The comparison says nothing about your process, and it closes down the conversation about alternatives that might have been cheaper. The first alternative worth testing is whether it has to be an installed app at all — the choice between a web app or a mobile app is settled by where the user physically stands at the moment of use.

Write the goal in a form you can verify six months after launch. One sentence is enough, and that sentence becomes the reference point in every later argument about scope.

That sentence, plus a list of the systems the app has to connect to and your budget and timeline range, is the full set of information for a first meeting. Everything else gets organised by a software project brief, and if you would rather talk it through first, start with a conversation.

Scope and requirements: what you settle before the first line of code

This is where you make the one decision nobody can make for you: what does not go into the first release. A business analyst turns your knowledge of the process into requirements, but you decide the priorities, because only you know what it costs your business to go without a given feature.

The practical tool here is MoSCoW — sorting features into Must have, Should have, Could have and Won’t have. The last category is the one that matters. Until there is a written list of the things you are deliberately not building, each of them comes back halfway through development as “surely that was obvious”. Choosing which features make the first release is covered separately in the guide on setting an MVP scope.

Requirements are written as user stories in the template “As a [role] I want [feature] so that [benefit]”, with acceptance criteria attached to each one. A good criterion is a question you can answer YES or NO — “after three wrong PIN attempts the account locks for 15 minutes” can be ticked off, “login must be secure” cannot. The approved backlog is also the basis for the estimate, so its level of detail determines how credibly a studio can answer the question of mobile app development cost. It also decides which billing model fits, because fixed price and time and materials split the risk of a wrong estimate between the two sides differently.

Your own time at this stage is usually a few workshops plus a backlog review. If scope approval slips by a week, the whole schedule slips by that week: the team has nothing to work on, and booked developer time rarely waits around.

UX/UI design: the prototype you click before any code exists

The design stage ends with a clickable prototype — a set of wireframes you move through as if it were the finished app, even though there is no code underneath. Prototypes are built in Figma, Sketch or Adobe XD, and this is the point where changes are cheapest: moving a button is minutes of work rather than rebuilding a screen.

Your input is content, brand assets and comments. Collect them in one round from everyone on your side and hand them over as a single list. Comments trickling in one at a time over two weeks mean the designer returns to the same screen several times, and the bill for those return trips is yours.

Click through the prototype as a user seeing the app for the first time with something specific to get done — not as somebody who knows the project from the inside. Approving the prototype closes the discussion about screen layout; reopening it during coding is the single most common reason projects go over budget.

Development in sprints and the team you are paying for

Development normally runs in two-week sprints under an Agile method — Scrum or Kanban — and each sprint ends with a working slice of the app you can install on a phone. Your job is to install that build and look at it, not to wait for the final version.

A typical team is a product or project manager, a business analyst, a UX/UI designer, an iOS developer, an Android developer, a backend developer and a QA engineer. The manager watches scope and deadlines, the analyst translates your process into requirements, the designer is responsible for whether the app makes sense to use, the mobile developers build what the user sees, the backend handles data and server-side logic, and QA checks that the whole thing works on real devices. Headcount depends on the technology: native means Kotlin or Java for Android and Swift for iOS separately, while cross-platform — React Native, Flutter, or Kotlin Multiplatform, which JetBrains declared stable in November 2023 — lets one team cover both platforms. Ask for those roles by name as an annex to the contract; that request, and six others, is what the guide on how to choose a software house puts to a studio at the first meeting.

At this stage you supply content, test data and access to the systems the app needs to exchange data with. This is usually the most underestimated client obligation: getting access to the API of a warehouse system or an ERP can take longer than writing the connection itself, which is why system integration starts with establishing who on the vendor’s side is responsible for granting access. Book yourself realistic time for the review after each sprint — it is the only place where you can correct direction without rewriting finished code, and the effect of those reviews on the schedule is covered in the guide on how long an app takes to build.

Testing and sign-off: how to check the app does what it was meant to

Sign-off means walking through the list of acceptance criteria from the backlog and marking each one YES or NO, with no debate about impressions. The QA engineer tests the app beforehand on devices and edge-case scenarios, but you are the one who confirms that the app supports your process.

Plan testing with the people who will actually use the app: warehouse staff, sales reps, field engineers. On iOS this runs through TestFlight, part of the Apple Developer Program, which lets you invite up to 10,000 external testers; Google Play has its own test tracks — internal, closed and open.

Agree up front how much time you have for testing and who runs it, because it is the item most often missing from the client’s calendar. Split the findings into defects — a mismatch with an approved criterion — and scope changes, meaning things nobody mentioned earlier. The first group is fixed by the studio as part of sign-off; the second goes into the backlog as features deferred past the first release.

Release: who should own the developer accounts

The Google Play Console and Apple Developer Program accounts should be registered to your company, with the studio added as a user with permissions. Google Play Console is a one-off $25 fee, the Apple Developer Program $99 per year. This is the only place your app really lives: versions, statistics, reviews and payouts. When the account belongs to the software house, changing supplier turns into a negotiation for access to your own product, and moving an app between accounts is a separate, tedious procedure.

Open the accounts early, because verification can take time. Google requires developer identity verification and may ask for an identity document plus a credit card issued in the same name — prepaid cards are not accepted. It is worth having that done before the app is ready.

The two stores then behave differently. Apple reviews every app manually through App Review, so both the initial release and every update need time allowed for a human assessment and a possible rejection with reasons. Google Play leans more on automated checks, which can make the path shorter, but the formal requirements are just as concrete: description, screenshots, privacy policy and the data safety form.

Prepare the material the studio will not supply for you: a privacy policy that matches the data you genuinely collect, company details for the developer profile, and a support contact for users. This section is informational and is not legal advice — have your privacy policy reviewed by a lawyer.

Maintenance and evolution: what happens to the app after launch

After launch the app needs maintenance whether or not you add new features to it. The standard scope is availability monitoring, security updates, backups and handling user reports in line with an agreed SLA. New feature work is a separate budget, and it is worth splitting the two lines in the contract so that fixes do not compete for the same hours as new ideas.

Some updates are forced by the stores. From 31 August 2026, new apps and updates on Google Play must target Android 16 (API 36) or higher, while apps already in the store must target Android 15 (API 35) to stay available to new users on newer devices. Wear OS and Android Automotive require API 35, Android TV and Android XR require API 34, and you can request an extension in the Play Console until 1 November 2026.

The practical planning conclusion is that an annual app budget has three lines: maintenance, forced platform updates, and development. Leaving out the first two is the most common reason an app becomes unavailable to part of its user base a year after launch, and the structure of those costs is broken down in the guide on what goes into an app quote.

Finally, settle one organisational point: who on your side collects user feedback and decides what goes into the next release. Without that person, store reviews and staff comments dissolve into inboxes, and the next version gets built around whoever complained most recently.