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 requires a Mac or PC to re-sign apps every seven days. 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 immediately stop working with an “app cannot be opened” error. Scarlet iOS mitigates this with automatic certificate rotation.
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.
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 to prevent unauthorized copying. Sideloaded apps bypass FairPlay because they are installed via a different mechanism that does not use App Store purchase validation.
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 and have restrictions on the number of apps that can be signed 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.
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 uses Apple’s enterprise certificate infrastructure to install apps outside the App Store. Scarlet iOS serves similar distribution needs at a smaller scale without requiring MDM infrastructure.
MFi (Made for iPhone)
Apple’s certification program for accessories. MFi-certified controllers, cables, and other accessories are guaranteed to work with iOS. 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.
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 are valid for a full year rather than seven days, can install an unlimited number of apps, and can access all development APIs. Scarlet iOS’s certificate management system provides comparable convenience without requiring users to purchase their own developer accounts.
Provisioning Profile
A file that associates a developer certificate with a specific device and bundle ID. Provisioning profiles are part of Apple’s code signing system and are required for any app 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.
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 still require App Store 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 specific iOS versions and devices. 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.
UUID (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, UDIDs are sometimes required when using free developer accounts to register a device for app signing.
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 the Scarlet iOS community forums — 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.