WhatsApp for iOS 6 was compiled as a 32-bit binary. An analysis of the Mach-O header would typically reveal support for:
Installing WhatsApp on iOS 6 in the current year is a challenging project for retro-tech enthusiasts. While the official app store version has long been discontinued for older firmware, the "WhatsApp IPA for iOS 6" remains a highly sought-after file for those looking to breathe life into an iPhone 3GS, iPhone 4, or iPhone 4S. The Reality of WhatsApp on iOS 6 whatsapp ipa ios 6
Install this tweak from Cydia to allow the installation of unsigned IPA files. WhatsApp for iOS 6 was compiled as a 32-bit binary
Why did they drop support? Because WhatsApp introduced end-to-end encryption, voice/video calling, and modern protocols that iOS 6’s outdated SSL/TLS libraries simply cannot handle. The Reality of WhatsApp on iOS 6 Install
Even if you successfully install a patched IPA, functionality remains limited compared to modern smartphones.