Scarlet iOS Glossary: Every Term Explained

The Complete Scarlet iOS and iOS Sideloading Glossary

The world of iOS sideloading comes with its own vocabulary. Terms like “IPA file,” “certificate revocation,” “entitlements,” and “provisioning profile” appear constantly in guides and community discussions, but are rarely explained for newcomers. This glossary provides clear, accurate definitions for every term you are likely to encounter when using Scarlet iOS or exploring iOS sideloading.

Bookmark this page and refer to it whenever you encounter an unfamiliar term. Understanding the terminology makes troubleshooting faster, community discussions more accessible, and your overall sideloading experience smoother.

A–E

AltStore

A competing third-party app installer for iOS that requires a computer running the AltServer application to function. Unlike Scarlet iOS, AltStore Classic needs a Mac or PC running AltServer to refresh apps signed with a free Apple ID every seven days. In the EU, AltStore PAL is a separate alternative app marketplace that needs no computer. It is one of the oldest and most established sideloading tools, though its computer dependency makes it less convenient than Scarlet iOS for most users. See our comparison of Scarlet iOS vs TrollStore and other alternatives for context.

App Store

Apple’s official marketplace for iOS applications. All apps submitted to the App Store undergo Apple’s review process before being made available for download. Apps that violate Apple’s guidelines or use restricted APIs cannot be distributed through the App Store.

Bundle ID

A unique identifier for an iOS app in the format com.developer.appname. The Bundle ID is embedded in the IPA file and used by iOS to identify the app. Two apps cannot have the same Bundle ID on one device unless one replaces the other.

Certificate

A cryptographic credential issued by Apple that is used to sign iOS apps. Apple issues certificates to registered developers and enterprises. When you install a sideloaded app, it is signed with a certificate that iOS verifies before allowing the app to run. Certificates have expiry dates and can be revoked by Apple.

Certificate Revocation

The process by which Apple invalidates a signing certificate before its normal expiry date. When a certificate used to sign sideloaded apps is revoked, those apps stop opening: they close right after you tap them, or iOS shows a message such as “Unable to Verify App” or that the app is no longer available. Scarlet iOS works again once it is signed with a new certificate, after which you reinstall affected apps.

Code Signing

The process of cryptographically attaching a developer certificate to an iOS app. iOS requires all apps to be properly code-signed before they can be installed and run. Sideloading tools like Scarlet iOS perform code signing using their own certificates rather than the developer’s original certificate.

Cydia

A now-discontinued third-party app store for jailbroken iOS devices. Cydia was the dominant app distribution platform for jailbroken iPhones for over a decade. It is mentioned frequently in older sideloading guides but is not relevant to Scarlet iOS, which does not require a jailbreak.

Decrypted IPA

App Store apps are encrypted with Apple’s DRM (FairPlay). A decrypted IPA has had this encryption removed, allowing the app to be re-signed and installed on other devices. Decrypted IPAs are required for sideloading App Store apps: the original encrypted versions cannot be re-signed.

Developer Mode

A setting Apple added in iOS 16 that must be turned on before apps signed with a development certificate, such as apps signed with your own Apple ID through SideStore, AltStore, Sideloadly or Xcode, will open. Scarlet iOS itself does not need Developer Mode. See when Developer Mode is needed.

Enterprise Certificate

A certificate from Apple’s Developer Enterprise Program, meant for companies to install their own in-house apps on employees’ devices without the App Store and without registering each device. Scarlet iOS installs as an enterprise-signed app, which is why you trust its developer under Enterprise App in VPN & Device Management, and why Apple can revoke it. A development certificate, by contrast, only works on registered devices.

Entitlements

A configuration within an iOS app that specifies which Apple services and system capabilities the app is permitted to access, such as iCloud, Push Notifications, Apple Pay, or HealthKit. Entitlements are signed into the app at build time and cannot be changed without re-signing. Some advanced capabilities require explicit Apple approval to include in entitlements.

F–J

FairPlay

Apple’s digital rights management (DRM) technology applied to App Store purchases. FairPlay encrypts app binaries so they only run for the Apple ID that downloaded them. That is why an App Store app has to be decrypted before it can be re-signed and sideloaded (see Decrypted IPA).

Free Developer Account

An Apple ID registered as a developer without paying the $99/year fee. Free developer accounts can sign apps, but those apps expire after seven days, only three of them can be active on a device at a time, and only 10 app IDs can be registered per week. Some sideloading tools use free developer accounts to sign apps, requiring weekly renewal.

IPA File

An iOS App Store Package: the file format for iOS applications. IPA files are essentially ZIP archives containing the compiled app binary, resources, and signing information. When you install an app via Scarlet iOS, you are installing an IPA file. IPA files have the .ipa file extension.

Impactor

Cydia Impactor is an older desktop tool for sideloading iOS apps from a computer. It has largely been superseded by newer tools like Sideloadly, AltStore, and Scarlet iOS. It is mentioned in older guides but is generally considered outdated as of 2026. Our Scarlet iOS vs Cydia Impactor comparison explains the difference.

Jailbreak

The process of removing Apple’s software restrictions from an iOS device, typically by exploiting a security vulnerability. Jailbreaking allows root-level access to the device filesystem and the ability to install software with no restrictions. Unlike Scarlet iOS, jailbreaking voids warranties, introduces security risks, and can cause device instability. Scarlet iOS explicitly does not require a jailbreak.

K–O

MDM (Mobile Device Management)

A type of software used by enterprises to manage iOS devices, including remotely installing or removing apps, enforcing security policies, and monitoring usage. MDM can push App Store apps as well as an organization’s own in-house apps signed with its enterprise certificate. Scarlet iOS does not use MDM and does not ask you to install a management profile.

MFi (Made for iPhone)

Apple’s certification program for accessories. MFi-certified controllers, cables, and other accessories are certified by Apple to work with iOS devices. In the context of emulators, MFi refers specifically to certified game controllers that have native iOS support without requiring additional configuration.

Unc0ver / Checkra1n / Palera1n

Names of popular jailbreaking tools. These are mentioned here because users sometimes encounter them in sideloading discussions. They are distinct from Scarlet iOS: they are jailbreak tools that require exploiting iOS vulnerabilities. Scarlet iOS does not use these tools and is not related to the jailbreak ecosystem.

Notarization

Apple’s baseline check of apps distributed outside the App Store in regions where alternative app marketplaces are allowed (the EU since iOS 17.4, and later Japan and Brazil). Apple scans notarized apps for malware and basic integrity but does not review their content. Apps installed through Scarlet iOS are not notarized.

OTA (Over the Air)

Distribution of software updates or app installs delivered via Wi-Fi or cellular network rather than requiring a cable connection to a computer. Scarlet iOS delivers all installs OTA: you never need to connect your iPhone to a computer.

P–R

Paid Developer Account

Apple’s standard $99/year developer program membership. Paid accounts can sign apps that stay valid for up to a year rather than seven days, are not limited to three active apps, and can register up to 100 devices of each type per year. Scarlet iOS avoids the need for your own developer account by signing apps for you, but its certificates can be revoked.

Provisioning Profile

A file (.mobileprovision) that ties a signing certificate to an app ID and, for development and ad hoc builds, to a list of registered devices; enterprise profiles work on any device. Every app installed outside the App Store needs one embedded to run on an iPhone. When Scarlet iOS installs an app, it manages provisioning profiles automatically behind the scenes.

Re-signing

The process of replacing an app’s original code signature with a new certificate. Re-signing is required when distributing apps outside the App Store because the original developer’s certificate is not transferable. Sideloading tools like Scarlet iOS re-sign every app they install with their own managed certificates. For the practical methods, see five ways to install apps outside the App Store.

Repository (Repo)

A server-hosted catalog of apps available for installation through Scarlet iOS. Repositories contain IPA files along with metadata (app name, description, version, icon) that Scarlet iOS displays in its browser. Different repos specialize in different categories: gaming, productivity, social media tweaks, etc.

ROM

In the emulation context, a ROM is a file containing the data from a physical game cartridge or disc, used to run games in an emulator. ROMs are required to play games on emulators installed via Scarlet iOS. The legality of ROMs varies by jurisdiction.

S–Z

Sideloading

The practice of installing apps on a device through a method other than the official app store. On iOS, sideloading refers to installing IPA files outside of the App Store using tools like Scarlet iOS. Sideloading is distinct from jailbreaking: sideloaded apps operate within iOS’s normal security sandbox.

Signing Certificate

See “Certificate.” These terms are used interchangeably in the sideloading community.

Substrate / Substitute

Mobile Substrate (and its replacement Substitute) are jailbreak frameworks that allow tweaks to inject code into other apps. These are only relevant on jailbroken devices and are not related to Scarlet iOS’s functionality.

TestFlight

Apple’s official beta testing platform. Developers submit test builds through TestFlight for distribution to testers. TestFlight builds expire after 90 days, and builds sent to external testers go through Apple’s Beta App Review. It is Apple’s officially supported alternative to direct sideloading.

TrollStore

A permanent app installer for specific iOS versions that uses a CoreTrust vulnerability to install apps that never expire. TrollStore apps do not require periodic certificate renewal, unlike standard sideloaded apps. However, TrollStore only works on iOS 14.0 beta 2 through 16.6.1, 16.7 RC and 17.0, not on iOS 18, iOS 26 or iOS 27. See our Scarlet iOS vs TrollStore comparison for a detailed breakdown.

Tweak

A modified version of an existing app that adds features, removes limitations, or changes behavior. In the sideloading community, tweaks typically refer to modified versions of App Store apps (e.g., Spotify++, YouTube ReVanced) distributed as IPA files through tools like Scarlet iOS.

UDID (Unique Device Identifier)

A hardware identifier for your iPhone used in developer provisioning profiles to specify which devices a signed app can run on. In the context of sideloading, a UDID is needed to register a device on a paid Apple Developer account, so apps signed with that account can run on it. See how to find your iPhone UDID.

Using This Glossary

Understanding these terms makes every other Scarlet iOS guide and community discussion more accessible. When you encounter a term in a troubleshooting thread or installation guide that is not here, search sideloading communities and the tools’ own documentation: the vocabulary of iOS sideloading is constantly expanding as the technology evolves.

Ready to put this knowledge to work? Download Scarlet iOS and start exploring the full potential of your iPhone today.