iOS：应用在完全删除后仍保留数据
我注意到应用在被删除后仍然保留信息。这意味着即使我们删除了应用，仍然会被该应用追踪。
例如，如果我删除了WhatsApp或Instagram，并选择删除所有数据，然后重启手机并重新安装该应用，它会自动识别我的账户。
显然，它使用了一种持久化机制。
我尝试了解是哪种机制。
- UIDevice.identifierForVendor
苹果明确表示，当同一供应商的所有应用被删除时，这个标识符会被更改。我进行了测试，因此这个标识符并不是罪魁祸首。
- DCDevice.generateToken
这个只在设备上存储2位信息，因此不足以存储用户名。
- 钥匙串服务（密码）
我在密码应用中检查过，没有为这些应用保存密码。
- iCloud 钥匙串
我关闭了这个功能。
有没有人知道应用在完全删除后仍然如何持久化数据的技术方式？苹果对我最大的吸引力之一就是隐私，因此我想了解这个问题……
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I noticed that apps retain info after being deleted. That means we are tracked by the app even after we deleted it.<p>For example, if I delete whatsapp or instagram, choosing to delete all data, then restart the phone and reinstall the app, it will automatically know my account.<p>So there is clearly a persistence mechanism that it uses.<p>I tried to understand which one.<p>- UIDevice.identifierForVendor
Apple clearly states this identifier is changed as soon as all apps from the same vendor are deleted. that's what I tested, so this identifier is not the culprit<p>- DCDevice.generateToken
This only stores 2 bits on the device, so not enough to store a username<p>- Keychain services (password)
I checked in the password app, no password was saved for these app<p>- iCloud Keychain
I turned off this feature<p>Does anyone know the technical way apps persist data even after total deletion? One of the big appeals of Apple to me is privacy, so I'd like to understand this...