FLEX

Free plan iPhone

What FLEX is

FLEX is a free, open-source debugging and exploration tool for iOS development. It runs inside the app being examined and places a toolbar above it, where developers can view and change application state. FLEX can inspect views, find live objects in memory, show their properties and ivars, modify them, and call methods. Its network history displays timing, headers, and responses for requests made using NSURLConnection or NSURLSession. Developers can also browse app files and SQLite or Realm databases, and inspect or edit NSUserDefaults values. FLEX 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. It supports Objective-C and Swift, and requires an app targeting iOS 9 or later. The project advises keeping 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.

Who it suits

FLEX suits iOS developers who need to inspect app state, views, network activity, files, databases, or preferences while an app runs. It is intended for development and debugging, not inclusion in Release builds.

What it does well

Inspects and modifies views and live objects.
Shows network timing, headers, and responses.
Browses SQLite and Realm databases.
Works on simulators and physical iOS devices.
No LLDB, Xcode, or remote server connection required.

What to know first

Requires an app targeting iOS 9 or later.
Does not support tvOS out of the box.
Project advises excluding it from Release builds.

Limits

FLEX requires an app that targets iOS 9 or higher. It does not support tvOS out of the box, and the project advises excluding it from Release builds because exposing it to app users may cause App Store rejection.

Plans

Plan	Billed and limits	Price
FLEX	Open-source iOS debugging library · iOS 9 or higher	Free

As engineering.flipboard.com lists them, read 8 Oct 2026. The maker's own page has the final word.

Getting started

Choose an installation route: CocoaPods, Carthage, Buck, manual Xcode integration, or Swift Package Manager.
Integrate FLEX into an app that targets iOS 9 or higher.
Run the app in the iOS Simulator or on a physical iOS device.
Use FLEX’s in-app toolbar to inspect or modify application state.
Exclude FLEX from Release builds, as the project advises.

Verdict

FLEX provides in-app inspection for a wide range of iOS development tasks, without a remote debugging connection. Its iOS target requirement and Release-build caution matter when deciding where to include it.

Questions

How much does FLEX cost?

FLEX is free and open source. Its listed plan is free.

Which platforms does FLEX support?

It works in the iOS Simulator and on physical iOS devices. It does not support tvOS out of the box.

What languages does it support?

FLEX supports Objective-C and Swift.

Does FLEX require an LLDB or Xcode connection while in use?

No. It runs inside the app and does not require an LLDB or Xcode connection or a remote debugging server while in use.

How can FLEX be installed?

The project documents installation through CocoaPods, Carthage, Buck, manual Xcode integration, and Swift Package Manager.

What does the project say about Release builds?

It advises excluding FLEX from Release builds because exposing it to app users is not recommended and may cause App Store rejection.

Facts from FLEX's own pages

App settings: It can view and dynamically modify NSUserDefaults values. · github.com, 7 Oct 2026
Contributions: The project welcomes pull requests and directs contributors to its contributing guide. · engineering.flipboard.com, 8 Oct 2026
Device use: The maker says FLEX works in the simulator and on physical devices. · engineering.flipboard.com, 7 Oct 2026
File and database browsers: It can browse the app’s sandbox files and SQLite or Realm databases. · github.com, 8 Oct 2026
File and database browsing: FLEX can browse the app bundle or sandbox, and explore SQLite and Realm databases. · github.com, 7 Oct 2026
Founded: 2014 · engineering.flipboard.com, 28 Sept 2026
Heap exploration: FLEX can scan live allocated memory for objects and let developers inspect them. · github.com, 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. · github.com, 7 Oct 2026
In-app toolbar: It displays a toolbar in a window above the app, where developers can view and modify application state. · github.com, 8 Oct 2026
Installation: The project documents installation through CocoaPods, Carthage, Buck, manual Xcode integration, and Swift Package Manager. · github.com, 8 Oct 2026
Intended users: The maker describes FLEX as a tool for iOS development and debugging. · github.com, 7 Oct 2026
License and contributions: Flipboard announced FLEX as open source and welcomed pull requests. · engineering.flipboard.com, 7 Oct 2026
Minimum target: FLEX requires an app that targets iOS 9 or higher. · github.com, 8 Oct 2026
Network debugging: Its network history can show requests made using NSURLConnection or NSURLSession, including timing, headers, and responses. · github.com, 7 Oct 2026
Network history: Network debugging can show request timing, headers, and full responses for requests made using NSURLConnection or NSURLSession. · github.com, 8 Oct 2026
NSUserDefaults: Developers can view and dynamically modify NSUserDefaults values; supported editable values include strings, numbers, arrays, and dictionaries. · github.com, 8 Oct 2026
Object inspection: It can find live objects on the heap, show their properties and ivars, modify them, and call methods. · github.com, 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. · engineering.flipboard.com, 8 Oct 2026
Platform limit: FLEX does not support tvOS out of the box. · github.com, 7 Oct 2026
Purpose: FLEX is an in-app debugging and exploration tool for iOS development. · engineering.flipboard.com, 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. · github.com, 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. · engineering.flipboard.com, 7 Oct 2026
tvOS support: FLEX does not support tvOS out of the box; the project points users to third-party forks for ports. · github.com, 8 Oct 2026
View inspection: Developers can inspect and modify views in the hierarchy and examine object properties and instance variables. · github.com, 8 Oct 2026

Where FLEX stands on Freedom251

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