Using TestFlight Alongside Scarlet iOS
Two Powerful Tools for Getting More Apps on iPhone
When it comes to installing apps beyond the standard App Store catalog, iPhone users have more options than ever. Two of the most useful (and often underutilized in combination) are Apple’s own TestFlight and third-party tools like Scarlet iOS. While they serve overlapping purposes, they work through entirely different mechanisms and have distinct strengths. Using them together gives you access to the widest possible range of apps and beta software.
This guide explains both tools, how they work, where each one excels, and how to run them side by side on the same iPhone without conflicts. Last checked: October 27, 2026, against Apple’s TestFlight pages for developers and testers.
TestFlight vs Scarlet iOS at a Glance
| TestFlight | Scarlet iOS | |
|---|---|---|
| Made by | Apple | A third-party developer |
| Which apps | Only betas a developer shares with you | IPA files you choose |
| Review | External betas may need Apple’s beta review | None |
| How long apps work | A build can be tested for up to 90 days | Until the certificate is revoked |
| Devices | Up to 30 devices per tester | The device you install on |
| Main risk | Pre-release bugs; some data may not carry over | Revocation; you are responsible for checking the IPA |
What Is TestFlight?
TestFlight is Apple’s official beta testing platform, acquired from Burstly in 2014 and deeply integrated into iOS. It allows developers to distribute pre-release versions of their apps to testers before the apps are ready for the App Store. TestFlight comes in two tiers:
- Internal Testing: Apple says up to 100 App Store Connect users with access to the app can test it. No review required.
- External Testing: Up to 10,000 users who are not on your team can participate. Apple says a build for external testers may have to pass a review first.
Apple adds that testers can use every beta build shared with them on up to 30 devices, and that each build can be tested for up to 90 days.
From the user’s perspective, TestFlight is extremely simple. You receive an invitation link from the developer, tap it on your iPhone, and the app installs just like an App Store app, automatically updating when new builds are published, showing clear versioning information, and collecting crash reports for the developer.
What Scarlet iOS Offers That TestFlight Does Not
TestFlight is limited to apps whose developers have specifically set up a TestFlight program. If a developer does not offer TestFlight access, you cannot use it to install their app. TestFlight also requires developer participation: the developer must actively invite you or publish a public link.
Scarlet iOS has no such restriction. If you have an IPA file, from almost any source, Scarlet can usually install it. This opens up:
- Apps that have been removed from the App Store
- Modified or patched versions of existing apps
- Apps from developers who do not offer TestFlight
- Older versions of apps
- Entirely unofficial apps that would never pass App Store review
Additionally, Scarlet iOS handles the signing process automatically, whereas TestFlight requires you to be on a developer’s explicit invite list. For a full picture of what Scarlet makes possible, see what Scarlet iOS is and how it works in 2026.
Running TestFlight and Scarlet iOS on the Same Device
The good news is that TestFlight and Scarlet iOS coexist peacefully on the same iPhone. There are no conflicts between them because they operate through entirely different installation channels. TestFlight apps have their own bundle IDs and use Apple’s native over-the-air installation system, while Scarlet iOS apps use enterprise or developer certificates through a separate pathway.
One practical point: Scarlet is enterprise-signed and does not need Developer Mode, and TestFlight apps do not need it either. If you also use a tool that signs with your own Apple ID (SideStore, AltStore, Sideloadly), those apps need Developer Mode; see our Developer Mode guide.
Potential Naming Collisions
The only scenario that can cause confusion is when you have both a TestFlight version and a Scarlet-installed version of the same app. iOS will treat these as the same app if they share a bundle ID, with the newer installation overwriting the older one. To run both versions simultaneously, the Scarlet-installed copy needs a different bundle ID, so that iOS treats them as separate apps. A copy with a different bundle ID starts with its own, empty data. See running multiple versions of the same app for how to change it.
Use Cases for Combining TestFlight and Scarlet iOS
App Development Workflow
If you are developing an iOS app, you might use TestFlight to distribute builds to your team and select beta users, while using Scarlet iOS to install development builds directly from IPA exports for personal testing. This gives you two separate channels that do not interfere with each other.
Running Beta and Stable Versions Together
Some apps offer TestFlight betas alongside their stable App Store version. If you want to run the TestFlight beta alongside a modified or older version of the same app, install the TestFlight version normally and install the alternative version through Scarlet iOS with a different bundle ID.
Accessing Geographically Restricted Betas
Occasionally, TestFlight betas are limited to specific regions. If you live outside the eligible region and the developer also offers the IPA file directly, Scarlet iOS can install it regardless of your device’s region setting.
How to Join TestFlight Betas
If you want to explore what TestFlight offers alongside Scarlet iOS, here is how to get started:
- Install the TestFlight app from the App Store if it is not already on your iPhone.
- Find a TestFlight beta link; developers often share these on their websites, social media, or through direct invitations.
- Tap the link on your iPhone. You will be taken to TestFlight with a prompt to accept the beta invitation.
- Tap Accept and then Install. If the invitation came by email, Apple’s tester guide says to open it and tap View in TestFlight.
- The app installs immediately. Apple notes that with TestFlight 3 or later you can turn on automatic updates so the latest beta builds install automatically.
Privacy: Apple’s tester page says that if you join through a public link, you do not have to give the developer your email address or other personal details, and that Apple also receives any feedback you send and can link it to your Apple Account.
Sending Feedback on a Beta
Giving feedback is the point of a beta. Apple’s steps: open the TestFlight app, tap the app in the Apps list, and tap Send Beta Feedback. You can also take a screenshot while using the beta and share it as feedback. Sideloaded apps from Scarlet have no such channel; report problems to whoever made the IPA.
Managing Apps from Multiple Sources
When you have apps from the App Store, TestFlight, and Scarlet iOS all on one device, organization becomes important. Here are some tips:
- Use iPhone’s App Library to keep your home screen clean regardless of install source
- Check the TestFlight app periodically to see if any beta invitations have expired
- Keep track of which apps you installed through Scarlet iOS, so you know what to reinstall if a certificate is revoked
- If you notice an app behaving unexpectedly, check whether the version is from TestFlight or Scarlet, as they may be different builds
For managing updates across all your sideloaded apps efficiently, see our guide on automating app updates for sideloaded apps on iPhone.
Limitations of TestFlight to Keep in Mind
- Beta builds can be tested for up to 90 days. Apple says the beta build stops opening once the testing period is over
- If a developer stops testing a build, you may lose access to it with little warning; to keep using the app, install the App Store version
- Apple says in-app purchases cost nothing only while you beta test, and they do not carry over to App Store versions
- TestFlight apps are limited to the platforms the developer has configured
- TestFlight requires an Apple ID and a working internet connection for the initial install
- Beta builds can have bugs that affect your data. Back up anything important in the app before joining a beta.
Scarlet iOS works differently. Once an app is installed through Scarlet, it remains on your device as long as the certificate is valid, regardless of what the developer does, though Apple can revoke certificates at any time. If that happens, see what to do when a certificate is revoked. Before installing an IPA from an unknown source, check it with our guide on how to scan IPA files for malware.
Conclusion
TestFlight and Scarlet iOS are not competing tools; they are complementary. TestFlight gives you legitimate access to developer-sanctioned betas with excellent update management. Scarlet iOS lets you install IPA files from other sources, including apps that TestFlight could never provide. Together, they cover most app installation scenarios you might encounter, as long as you keep their different risks in mind. Scarlet is confirmed on iOS 14 through iOS 26; iOS 27 support is reported by third parties but not officially confirmed.
To set up the Scarlet side, see how to install Scarlet iOS, or open our Scarlet iOS install page in Safari.
FAQ
Does installing a TestFlight beta delete my App Store version?
The beta takes the App Store app’s place, because it is the same app. When testing ends, Apple says to install the App Store version again from the App Store. Back up first in case some data does not carry over.
Can Scarlet install a TestFlight-only app?
No. TestFlight builds are delivered by Apple to invited testers; there is no IPA to import unless the developer publishes one separately.
Is TestFlight safer than Scarlet?
TestFlight apps come from the developer through Apple, and external betas may be reviewed. Scarlet installs whatever IPA you give it, so how safe that is depends on where the file came from.