APP SPECIFICATION PLATFORM

Most app ideas die before a developer sees them.
Yours won't.

Tarn takes you from first instinct to a structured, developer-ready specification — through structured conversation, not a blank document. No UX experience required.

Start building free → See how it works

THE PROBLEM

Most people with an app idea hand a developer a paragraph and hope for the best. Six months and a budget later, they get something that almost solves the problem they had.

The gap isn't technical ability. It's the spec. A good specification is the difference between a developer who builds exactly what you imagined and one who builds a reasonable interpretation of it. Tarn closes that gap — without requiring you to become a product manager.


HOW IT WORKS
01

Describe your idea in your own words

No template to fill in. No jargon to learn. Tarn starts with a question and builds from there — extracting goals, design direction, and scope from what you tell it.

02

Tarn structures it into cards

Goals, design tokens, references, and constraints each get their own card. You confirm what stays, edit what doesn't, and Tarn asks the right questions — in plain English, no expertise required.

03

You resolve the open questions

Every decision you haven't made yet sits as an open question in MISSION. Tarn helps you answer them — one at a time, without overwhelm.

04

Export a spec your developer can use

A structured spec.md and tokens.json pair. Everything a developer needs — goals, flows, design system, constraints — in one handoff document.


THE BUILD PIPELINE

Nine structured layers, unlocked as you need them. B0 and B1 are free, forever. Each additional column adds depth without complexity.

B0FREE
B1FREE
B2£4/mo
B3£6/mo
B4£8/mo
B5£6/mo
B6£5/mo
B7£4/mo
B8£20

B4 — Design Language — is the v1 hero column. B7 — Ready to Ship — is pay-per-project.


WHAT YOU GET
📋

SPEC.MD

A human-readable specification covering goals, design system, scope boundaries, and open questions. Ready to hand to a developer.

🎨

TOKENS.JSON

Every design decision as a structured token file — colours, typography, spacing. Drop it straight into a design system or codebase.

🎯

MISSION DECISIONS

A record of every decision made and every question resolved — so nothing gets misinterpreted six months into the build.

TIME SAVED

Tarn tracks your active session time and shows the equivalent senior UX director hours you've saved — at the export screen.


PRICING

Start free. Unlock what you need. Column subscriptions are per account, not per project.

B0 + B1 — References & User Goals
Unlimited projects. Full spec export included.
FREE
B4 — Design Language
Colour, typography, tone of voice. The v1 hero column.
£8/mo
Prototype generation
A working app prototype built from your design tokens and goals. Hosted and shareable.
£2/generate
Full bundle — B0 through B7
Everything except Code Generation (B8).
£19–25/mo
Founder / beta rate
All columns, locked forever at beta pricing. Limited places.
~£9/mo
B8 — Code Generation
A structured code scaffold from your full spec.
£20/project

Your idea has been waiting for a process.
This is it.

Tarn won't write your spec for you. It will ask the right questions until you've written it yourself — and then give you something you can hand to a developer with confidence.

Start building free →