FLEX
FLEX is a free, open-source debugging and exploration tool for iOS development, written for Objective-C and Swift.
What FLEX is
FLEX is a free, open-source debugging and exploration tool for iOS development, written for Objective-C and Swift. It runs inside the app being examined and opens a toolbar in a window above it, allowing developers to inspect and change application state while the app runs. Developers can inspect views, find live objects in memory, examine their properties and ivars, modify them, and call methods. Network history shows timing, headers, and responses for requests made with NSURLConnection or NSURLSession. FLEX can also browse an app bundle or sandbox, explore SQLite and Realm databases, and view or dynamically change NSUserDefaults values. It works in the iOS Simulator and on physical iOS devices without an LLDB or Xcode connection or a remote debugging server. Installation options include CocoaPods, Carthage, Buck, manual Xcode integration, and Swift Package Manager. The app must target iOS 9 or higher. The project advises leaving FLEX out of Release builds because exposing it to app users is not recommended and may lead to App Store rejection. It does not support tvOS out of the box.
Good
- Inspects and modifies views and live objects.
- Shows network timing, headers, and responses.
- Browses app files and SQLite or Realm databases.
- Works in the simulator and on physical iOS devices.
- Runs without an LLDB or Xcode connection.
Watch out
- Apps must target iOS 9 or higher.
- tvOS is not supported out of the box.
- The project advises excluding FLEX from Release builds.
Who it suits
FLEX is for iOS developers who need to examine and change an app’s runtime state, network activity, files, or databases. It is suited to projects using Objective-C or Swift.
Verdict
FLEX puts inspection tools inside an iOS app, covering views, memory, network requests, files, databases, and settings. Keep it out of Release builds as the project advises, and note that tvOS support is not built in.
Plans and prices
From FLEX's own pricing page, checked 8 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| FLEX | Free | Open-source iOS debugging library · iOS 9 or higher |
The facts
Each one read from FLEX's own pages, with the date it was checked.
Where it runs
- App settings
- It can view and dynamically modify NSUserDefaults values.checked 7 Oct 2026
- Device use
- The maker says FLEX works in the simulator and on physical devices.checked 7 Oct 2026
- File and database browsers
- It can browse the app’s sandbox files and SQLite or Realm databases.checked 8 Oct 2026
- In-app toolbar
- It displays a toolbar in a window above the app, where developers can view and modify application state.checked 8 Oct 2026
- Platform limit
- FLEX does not support tvOS out of the box.checked 7 Oct 2026
- tvOS support
- FLEX does not support tvOS out of the box; the project points users to third-party forks for ports.checked 8 Oct 2026
What it does
- Contributions
- The project welcomes pull requests and directs contributors to its contributing guide.checked 8 Oct 2026
- File and database browsing
- FLEX can browse the app bundle or sandbox, and explore SQLite and Realm databases.checked 7 Oct 2026
- Heap exploration
- FLEX can scan live allocated memory for objects and let developers inspect them.checked 8 Oct 2026
- How it works
- It presents a toolbar in a window above the running app, where developers can view and modify application state.checked 7 Oct 2026
- Installation
- The project documents installation through CocoaPods, Carthage, Buck, manual Xcode integration, and Swift Package Manager.checked 8 Oct 2026
- Intended users
- The maker describes FLEX as a tool for iOS development and debugging.checked 7 Oct 2026
- License and contributions
- Flipboard announced FLEX as open source and welcomed pull requests.checked 7 Oct 2026
- Minimum target
- FLEX requires an app that targets iOS 9 or higher.checked 8 Oct 2026
- Network debugging
- Its network history can show requests made using NSURLConnection or NSURLSession, including timing, headers, and responses.checked 7 Oct 2026
- Network history
- Network debugging can show request timing, headers, and full responses for requests made using NSURLConnection or NSURLSession.checked 8 Oct 2026
- NSUserDefaults
- Developers can view and dynamically modify NSUserDefaults values; supported editable values include strings, numbers, arrays, and dictionaries.checked 8 Oct 2026
- Object inspection
- It can find live objects on the heap, show their properties and ivars, modify them, and call methods.checked 7 Oct 2026
- Operation
- FLEX runs inside the app and works in both the simulator and on physical devices without an LLDB/Xcode connection or remote debugging server.checked 8 Oct 2026
- Purpose
- FLEX is an in-app debugging and exploration tool for iOS development.checked 8 Oct 2026
- Release-build caution
- The project advises excluding FLEX from Release builds because exposing the tool to app users is not recommended and may cause App Store rejection.checked 8 Oct 2026
- Runtime requirement
- FLEX runs inside the app and does not require LLDB, Xcode, or a remote debugging server connection while in use.checked 7 Oct 2026
- View inspection
- Developers can inspect and modify views in the hierarchy and examine object properties and instance variables.checked 8 Oct 2026
The company
- Founded
- 2014checked 28 Sep 2026
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