App Overview

Sideline: Private 2nd Number icon

Sideline: Private 2nd Number

Pinger, Inc. · Utilities

Sideline gives you a second phone number for calling and texting—so you can stay connected without sharing your real number

Free · In-app purchases

PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.4
14,842 ratings · Top 30%

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

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What's included17 files

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

  • START_HERE
  • AGENTS
  • EVIDENCE
  • SPEC
  • BUILD_PLAN
  • DIFFERENTIATION
  • skills/
  • screens/
Preview a sample Build Kit No email needed

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 Sideline: Private 2nd Number: 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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App evidence

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

Screenshots

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App Store description

Sideline gives you a second phone number for calling and texting—so you can stay connected without sharing your real number. Get the app today to keep your personal number private. Whether you're working, selling online, or just want more control over who can reach you, Sideline makes it easy to separate your communications. Get a second phone number, send unlimited texts, and manage calls with powerful tools—all from one app. Sideline works over your carrier network (not VoIP), so your second number is as reliable as your first. Take control of your privacy and communication with Sideline. WHY SIDELINE? Protect Your Personal Number: - Get a second phone number for private calling and texting - Keep your real number separate and secure - Choose a local area code (or an area code of your choice) - Includes Caller ID and custom voicemail - Reliable cellular calling (not VoIP) Private Texting & Calling: - Send unlimited SMS and MMS messages - Use your second number for work, marketplace listings, or signups - Call and text without revealing your personal number - Access your number from multiple devices Stay in Control: - Auto-Reply sends instant responses when you miss a call - Custom voicemail with message transcripts - Port your existing number to Sideline - Block unwanted callers and manage contacts Smart Communication Tools: - Save and reuse frequently sent texts - Add notes to conversations and contacts - Stay organized without mixing personal and business messages USE SIDELINE FOR: - Private texting and calling - Work or business communications - Online buying and selling (Craigslist, Facebook Marketplace, etc.) - Protect your personal number FREQUENTLY ASKED QUESTIONS What is Sideline, and how does a second phone number work? Sideline is a second phone number app that lets you call and text from a separate number on your smartphone. Just download the Sideline app, and your Sideline number will work alongside your primary number, so you can keep personal and secondary communications separate without needing a second phone. Can I use Sideline for private texting and calling? Yes. Sideline is designed for private texting and calling, so you don't have to share your personal phone number with strangers and businesses. Use your second number for work, online selling, dating, or any situation where you want more privacy. Is Sideline reliable for calls and texts? Sideline uses your carrier's cellular network (not VoIP), which means your calls are clear and reliable—just like your regular phone number. You can send unlimited SMS and MMS messages and make calls with confidence. Can I choose or transfer my phone number? Yes. You can select a second phone number with an area code of your choice, or port (transfer) your existing number to Sideline. This makes it easy to keep a number you already use while gaining more privacy and features. Who is Sideline for? Sideline is for anyone who wants a second phone number to keep their personal number private and their communications organized—like professionals and business owners who don't want to carry a second phone, people buying and selling online who don't want to share their real number, freelancers who need to manage client communications—and anyone who values privacy and wants to control who can reach their real number. Do I need to provide a government-issued ID to create a Sideline account? No. You do not need to submit a government-issued ID to sign up for Sideline. Instead, you'll verify your account using two-factor authentication (2FA). DOWNLOAD SIDELINE TODAY Get a second phone number for private texting and calling. Stay connected—without giving out your personal number. LEGAL © 2026 Pinger, Inc. All rights reserved. The TextFree name, associated trademarks, and logos are trademarks of Pinger, Inc. or related entities. Terms of Service: https://www.sideline.com/terms-of-service/ Privacy Policy: https://www.sideline.com/privacy-policy/

Written user reviews are not shown here. Check current App Store reviews >

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

Allow users to choose area codes or custom numbers.

Assumption to check: Limited customization options for second numbers.

Validate with people who use this workflow before building.

Hypothesis 2

Implement better call routing algorithms.

Assumption to check: Inconsistent call quality reported.

Validate with people who use this workflow before building.

Hypothesis 3

Simplify subscription management and enhance visibility.

Assumption to check: Challenges in managing subscriptions.

Validate with people who use this workflow before building.

Hypothesis 4

Integrate in-app support and FAQs.

Assumption to check: No user support available within the app.

Validate with people who use this workflow before building.

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.

SUGGESTED BUILD STACK
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Zustand
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.