App Overview

Onoff Numbers icon

Onoff Numbers

ONOFFAPP · Utilities

What if you could get a second number in minutes, without the hassle of using a second phone or a second SIM card, but just by downloading an app? You dreamed of it, Onoff made it happen!

Free · In-app purchases

PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
4.6
774 ratings · Top 15%

Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.

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Build Kit

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A product spec, screen plans, and build steps for your coding agent.

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What's included18 files

A product spec, phased build plan, differentiation notes, and screen references.

  • START_HERE
  • AGENTS
  • EVIDENCE
  • SPEC
  • BUILD_PLAN
  • DIFFERENTIATION
  • skills/
  • screens/
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Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.

Feature spec

Goal: Send a clear invoice after finishing a job.

  • Add a client, line items, a due date, and payment instructions.
  • Preview the total before exporting a PDF.
  • Keep an editable draft if export fails.

Screen plan

Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.

States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.

Differentiate and validate

Hypothesis: Contractors need faster repeat invoices more than more templates.

First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.

The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.

Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.

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Quick prompt

> SELECT BUILD PLATFORM:

Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.

// RORK SYSTEM PROMPT
Rork plan preview for Onoff Numbers: map the core Utilities workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
            

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Opportunities

AI-GENERATED OPPORTUNITY HYPOTHESES

These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.

Hypothesis 1

Offer more flexible trial options.

Assumption to check: Limited free usage before needing to purchase

Validate with people who use this workflow before building.

Hypothesis 2

Implement a cleaner, more organized layout.

Assumption to check: User interface can feel cluttered

Validate with people who use this workflow before building.

Hypothesis 3

Optimize backend calls and improve loading times.

Assumption to check: Inconsistent performance issues

Validate with people who use this workflow before building.

Hypothesis 4

Provide in-app chat support for immediate assistance.

Assumption to check: Limited customer support options

Validate with people who use this workflow before building.

App evidence

Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.

App Store description

What if you could get a second number in minutes, without the hassle of using a second phone or a second SIM card, but just by downloading an app? You dreamed of it, Onoff made it happen! You will want to use a second number for: Having a separate professional line - separate your professional and personal life Protecting your privacy when you are online - your safety is our priority Selling goods online in total confidence - safely communicating with your potential buyers Carrying only one phone on you - less weight in your pocket, less hassle between switching the phones Being able to use your phone number from any smartphone and even from your web browser - we want you to have a number as flexible as your email! Make low-cost international calls - the world is just one call away With Onoff, you also have: -Calls and SMS -Integrated visual voicemail -Voice messages -Synchronization of all your contacts list -Possibility of porting an existing number, in order to use it in the Onoff App -An app compatible with all SIM cards to always call on the best network -Numbers from more than 30 countries available And there’s much more ! You can follow us on: Facebook - Linkedin - Twitter - Instagram In the application, you can subscribe to a number or a calling plan, the prices of which vary depending on the nationality or region chosen, as well as the duration (1, 3 or 12 months). Payment will be made through your iTunes account after confirmation of purchase, and will be withdrawn 24 hours before the end of each billing cycle. You can deactivate automatic renewal in the settings of the App Store after purchase, at least 24 hours before the end of the current subscription period. With your Onoff number, you can make unlimited calls throughout Europe. For communication outside of Europe, you can also purchase credits, valid for any destination! Any demonstration product offered within promotions will be automatically terminated upon first purchase. We cannot guarantee the systematic compatibility of numbers with verification services by SMS. Onoff: several numbers in one application, without changing the SIM card! See https://www.onoff.app/en/privacy-policy for the Privacy Policy. Onoff app Terms and Conditions can be found at https://www.onoff.app/en/terms-conditions/

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Screenshots

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Build scope

Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.

Define the first version

Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.

Set boundaries

Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.

Check the hard parts

Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.

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BUILD KIT DIFFICULTY
Advanced

From the Build Kit assessment.

A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.