How to Write an App Requirements Document in 2027: Template

What an app requirements document is, and how it differs from a brief

An app requirements document (in many countries called a technical specification) states exactly what the app must do and how you will know it is finished. Three people read it: you, the designer and the developer. When all three understand the text the same way, the biggest source of project disputes disappears: “I thought that was included.”

Do not confuse three documents. A brief answers “why” and “for whom”: the goal, the audience, the market, the budget. The requirements document answers “what exactly must work”: screens, actions, rules, data. The estimate answers “how much and when”, and it is built from the requirements. For a website we covered the brief in our website brief template. An app has more to pin down: the phone itself, the app stores, notifications, working without internet.

The good news: you do not need to write 80 pages like an engineer. Three to six pages of plain text following the template below is enough. The contractor adds the technical details, but nobody can invent for you what your business needs.

There is one more benefit. A written document gets you comparable quotes. When five studios price the same document, you can put the prices side by side. When each prices its own version of your idea, there is nothing to compare.

Mobile app specification template: 10 sections

Copy this list into a document and fill in every item, even if it is one or two sentences. An empty section is a question you will still have to answer, only later and at a higher price.

1. Goal and a measurable result. One sentence: “customers book on their own, and 30% of bookings come through the app.” A number is optional, but then write down how you will recognise success.
2. Users and roles. Who uses it: customer, stylist, administrator, courier. Each role gets its own screens and permissions.
3. Platforms. iOS, Android or both; whether you need a tablet version; whether a website that installs on the phone like an app (a PWA) is enough or you need the app stores. If you are unsure, first compare an app, a website and a PWA by cost and purpose.
4. Screen map. A list of every screen and arrows between them: sign-in, home, catalog, item page, cart, profile. A hand sketch photographed with a phone works.
5. User flows. What a person does, step by step: “opens the app, picks a service, picks a time, pays, gets a reminder.”
6. Features with priorities. Three columns: “cannot launch without it”, “nice to have”, “later”. This is the most important section for your budget.
7. Data and integrations. Where users and orders are stored, and what the app connects to: payments, CRM, accounting, maps, email, messengers.
8. Non-functional requirements. Speed, offline behaviour, languages, security, accessibility (more below).
9. Publishing and accounts. Whose name the developer accounts are opened in, who writes the store listing, which countries.
10. Acceptance and stages. How the result is checked, how many rounds of edits are included, how payment is split by stage.

For each item it helps to add examples of apps you like and one line on what exactly you like. “I want it like Uber” says nothing, while “I want the map with pins to look like Uber and sign-up to work by phone number” says everything.

Mobile app requirements: functional and non-functional

A requirements document normally holds two kinds of entries. Functional requirements describe what the app does: “a user can reschedule a booking up to 2 hours before it starts.” Non-functional requirements describe how well it does it: fast, secure, clear, in the right languages. The second kind is the one people forget most often, and then argue about.

Example for a salon booking app

Role “customer”. Sign-up by phone number with an SMS code. A service catalog with price and duration. Choice of stylist and free time slot. Card prepayment. Reminders 24 hours and 2 hours before. Free cancellation up to 24 hours before. Role “administrator”: stylist schedules, list of bookings, refunds, promo mailings.

That is the functional part. Add the non-functional part next to it:

• Speed. The home screen opens without a noticeable delay on an average phone that is five years old.
• Connection. What does the customer see without internet: the last booking or an error message? A full offline mode costs extra.
• Languages and currencies. How many interface languages, which currency for prices, how dates look.
• Security and data. Which personal data is stored, who can see it, how a person deletes their account. If you operate in your country, ask a lawyer about personal-data rules; in the EU that means GDPR.
• Accessibility. Large text, contrast, labels for screen readers. It is both convenience and a legal requirement in some markets.
• Devices. From which iOS and Android versions you support, and on which screen sizes you test.

Do not forget the “invisible” part: most apps have an admin panel where your team manages content and orders. Write it into the document as its own section, otherwise you will find the app is finished but you have nothing to run it with.

What to write about the App Store and Google Play

Publishing is a separate stage with its own rules, and it depends on more than us. So it is worth writing down a few points in advance.

• Developer accounts. Apple charges $99 a year, Google Play a one-time $25. We register the app under your account, so note who opens it and who keeps the credentials.
• A finished build for review. Under Apple’s rules (section 2.1, app completeness) you submit a finished build: no placeholders or temporary pages, with working links, and if there is a sign-in, a demo account for the reviewer, with the server side running at that moment. In the document this becomes an acceptance item: “test account and reviewer notes are ready.”
• Google Play testing. For new personal developer accounts Google requires closed testing: at least 12 testers opted in for 14 days in a row, and only then opens release to everyone. Build these two weeks into the schedule or open an organisation account; check the current terms in Google Play Help.
• Store text and images. Description, screenshots, privacy policy, age rating. Who writes them and in which languages.
• Payments. If the app sells digital goods or subscriptions, the stores have their own rules and commissions. Physical goods and services follow different rules. Write down what you sell, and your contractor will suggest the right setup.

Store review times are outside our control, so we never promise an exact date of appearing in the store. For the publishing steps themselves, see how to make an app: from idea to App Store.

Five mistakes in an app specification that raise time and cost

1. No priorities. When everything is “very important”, the estimate covers everything, and you launch version one in six months instead of two. Split features into “must”, “nice to have” and “later”.
2. No acceptance criteria. “Beautiful and convenient” cannot be tested. “A booking takes no more than four taps” can.
3. Admin and roles forgotten. The customer app is half the product. The other half is the tool your team uses.
4. Vague integrations. “Connect to the CRM” means different amounts of work for different systems. Name the system and describe which data goes where.
5. No single decision-maker. If three people on your side make decisions, the project stalls on approvals. Appoint one person who says yes or no.

Another common trap is writing the document for a finished “perfect product”. It is better to describe a first version that tests your idea on real people, and keep a separate list of everything you will add if it works. What such a first version looks like and what it costs is covered in what an MVP is and how much it costs.

Check whether your requirements are ready to be priced

Go through the short checklist below. It shows whether you can send the document to contractors or should close some gaps first. If you answer “no” to most items, do not worry: some questions can be worked through with the contractor, and we are ready for that.

Who should write it: you, the contractor, or both

There are three workable scenarios, and the choice depends on how clear your idea is.

• You write it yourself from the template. Fits a simple idea and an owner who knows their audience. You get several quotes and compare them.
• The contractor writes it from your brief. Convenient, but remember: the more detailed the document, the more accurate the estimate. A free specification often turns into a specification built around their price, so ask who owns it if you choose another team.
• Paid pre-project work. For complex products (roles, payments, several systems) we do this as a separate stage: an architecture session for €3,500. You get a product map, an estimate and a plan for the first version. The fee counts toward the project, and the map stays with you either way, even if you later choose another team.

If you need screens, not just text, add design and a prototype, from €1,990: a clickable prototype on a phone explains the idea better than ten pages of description. In our ready-made app packages the design is already included.

How to choose who to trust with the document and the project itself is covered in how to choose a web development company; the same questions work for app developers. And what the app itself costs is in app development cost.

What to choose in your situation

• The idea is simple: one flow, one role. Fill in the template yourself, send it to two or three teams and compare the answers. An iOS and Android app with us is from €10,900; the exact sum is calculated in the estimate after the document.
• You have several roles, payments, integrations. Do not write it all blind: start with an architecture session and get the requirements as a product map and estimate.
• You are not sure you need an app at all. A website on the phone or a Telegram mini app may be enough. Compare the options and their cost before you write the document.
• You already have a document from another studio. Show it to us and to other contractors: one document, several quotes. How to compare the answers fairly is in how to compare contractors and development quotes.
• You need to launch as fast as possible. Describe only the must-have features and leave the rest for version two.

Not sure where to start? Tell us the idea in a short message on the contact page, and we will say which format of start fits in your city or remotely.