Is there any limit in storing values in NSUserDefaults?

From iOS SDK codes, and related Apple official document..

extension UserDefaults {


    /*!
     NSUserDefaultsSizeLimitExceededNotification is posted on the main queue when more data is stored in user defaults than is allowed. Currently there is no limit for local user defaults except on tvOS, where a warning notification will be posted at 512kB, and the process terminated at 1MB. For ubiquitous defaults, the limit depends on the logged in iCloud user.
     */
    @available(iOS 9.3, *)
    public class let sizeLimitExceededNotification: NSNotification.Name


    // ....
 }   

---

Summary

1. Currently there is no limit for local user defaults
2. On tvOS, where a warning notification will be posted at 512kB, and the process terminated at 1MB.
3. For ubiquitous defaults, the limit depends on the logged in iCloud user.

There are limits on what types you may store: they must all be Property List objects, namely NSString, NSNumber, NSData, NSArray, and NSDictionary. Furthermore, you may only store NSArray and NSDictionary if the values are also property list objects; also, all the keys of the NSDictionary must be strings.

Note that an object like UIColor is not on the above list. So if you want to store a color in the defaults database, you'll need to convert it into a string or data object first, then convert it back when you read the defaults.

As far as size limits, there are none that are documented, but note that all data will be stored as a property list file. The entire file is read in and written out as a whole, so if you use NSUserDefaults to store a large amount of data that only changes in parts, you will be wasting a lot of time doing unnecessary I/O.

As long as there's enough space on the iPhone/iPad, you can store NSUserDefault values. All those values is stored into a .plist file, and this file is very small, most of the time under 1 kb (unless you store a lot of data).