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A simple way to detect at runtime if we're running in UIKit legacy mode or the new "flat" variant. Written for our PDF iOS SDK (, where the precompiled binary needs to detect at runtime in what variant it's running. Want more stuff like that? Follow me on Twitter:
// Taken from This snippet is under public domain.
#define UIKitVersionNumber_iOS_7_0 0xB57
BOOL PSPDFIsUIKitFlatMode(void) {
static BOOL isUIKitFlatMode = NO;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
// We get the modern UIKit if system is running >= iOS 7 and we were linked with >= SDK 7.
if (kCFCoreFoundationVersionNumber >= kCFCoreFoundationVersionNumber_iOS_7_0) {
isUIKitFlatMode = (NSVersionOfLinkTimeLibrary("UIKit") >> 16) >= UIKitVersionNumber_iOS_7_0;
return isUIKitFlatMode;
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nacho4d commented Dec 16, 2013

Awesome thread!

One tiny thing to add:

If kCFCoreFoundationVersionNumber_iOS_7_0 is undefined, use following snippet:

ifndef kCFCoreFoundationVersionNumber_iOS_7_0

define kCFCoreFoundationVersionNumber_iOS_7_0 847.2


Instead of the defining the var I would use the & ... like

if (&kCFCoreFoundationVersionNumber_iOS_7_0 &&
    kCFCoreFoundationVersionNumber >= kCFCoreFoundationVersionNumber_iOS_7_0) 
{ ...

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bgglenn commented Oct 2, 2014

For anyone googling their way here, 8.0 is 0xCF6.

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steipete commented Aug 5, 2016

iOS 9.3: 0xDB8
iOS 10b4: 0xE0C

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steipete commented Oct 1, 2018

For iOS 12 (GM), it seems that casting to unsigned integer is now required:

(lldb) p (int32_t)NSVersionOfLinkTimeLibrary("UIKit") >> 16
(int32_t) $4 = -4536
(lldb) p (uint32_t)NSVersionOfLinkTimeLibrary("UIKit") >> 16
(uint32_t) $5 = 61000

-> UIKitVersionNumber_iOS_12_0 = 0xEE48

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clementbarry commented Sep 30, 2021

iOS 15.0 is 0x13CB

(lldb) p (uint32_t)NSVersionOfLinkTimeLibrary("UIKit") >> 16
(uint32_t) $2 = 5067

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iOS 15.2 is 0x1455

(lldb) p (uint32_t)NSVersionOfLinkTimeLibrary("UIKit") >> 16
(uint32_t) $1 = 5205

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