diff --git a/README.md b/README.md
index 0c172ca..8e0d821 100644
--- a/README.md
+++ b/README.md
@@ -323,6 +323,11 @@ Available writing options:
 - `.escapeUnicode` — Escape non-ASCII characters as `\uXXXX`
 - `.newlineAtEnd` — Add trailing newline `\n`
 
+Non-standard options (unavailable when `strictStandardJSON` trait is enabled):
+
+- `.allowInfAndNaN` — Write `Infinity` and `NaN` literals
+- `.infAndNaNAsNull` — Write `Infinity` and `NaN` as `null` (takes precedence)
+
 ## Read and Write Options
 
 ### Reading Options
@@ -375,7 +380,7 @@ Available options:
 Non-standard options (unavailable when `strictStandardJSON` trait is enabled):
 
 - `.allowInfAndNaN` — Write `Infinity` and `NaN` literals
-- `.infAndNaNAsNull` — Write `Infinity` and `NaN` as `null`
+- `.infAndNaNAsNull` — Write `Infinity` and `NaN` as `null` (takes precedence)
 
 ## Package Traits
 
diff --git a/Sources/YYJSON/Configuration.swift b/Sources/YYJSON/Configuration.swift
index c7ec75b..108ba37 100644
--- a/Sources/YYJSON/Configuration.swift
+++ b/Sources/YYJSON/Configuration.swift
@@ -93,10 +93,14 @@ public struct YYJSONWriteOptions: OptionSet, Sendable {
 
     #if !YYJSON_DISABLE_NON_STANDARD
 
-        /// Write inf and nan number as 'Infinity' and 'NaN' literal.
+        /// Writes infinity and NaN values as `Infinity` and `NaN` literals.
+        ///
+        /// If you set `infAndNaNAsNull`, it takes precedence.
         public static let allowInfAndNaN = YYJSONWriteOptions(rawValue: YYJSON_WRITE_ALLOW_INF_AND_NAN)
 
-        /// Write inf and nan number as null literal.
+        /// Writes infinity and NaN values as `null` literals.
+        ///
+        /// This option takes precedence over `allowInfAndNaN`.
         public static let infAndNaNAsNull = YYJSONWriteOptions(rawValue: YYJSON_WRITE_INF_AND_NAN_AS_NULL)
 
     #endif  // !YYJSON_DISABLE_NON_STANDARD
diff --git a/Sources/YYJSON/Encoder.swift b/Sources/YYJSON/Encoder.swift
index 7ac2a0d..8640947 100644
--- a/Sources/YYJSON/Encoder.swift
+++ b/Sources/YYJSON/Encoder.swift
@@ -58,7 +58,8 @@ import Foundation
                 codingPath: [],
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: writeOptions
             )
 
             try value.encode(to: encoder)
@@ -135,6 +136,7 @@ import Foundation
         let userInfo: [CodingUserInfoKey: Any]
         let dateEncodingStrategy: DateEncodingStrategy
         let dataEncodingStrategy: DataEncodingStrategy
+        let writeOptions: YYJSONWriteOptions
 
         init(
             doc: UnsafeMutablePointer<yyjson_mut_doc>,
@@ -142,7 +144,8 @@ import Foundation
             codingPath: [CodingKey] = [],
             userInfo: [CodingUserInfoKey: Any] = [:],
             dateEncodingStrategy: DateEncodingStrategy = .deferredToDate,
-            dataEncodingStrategy: DataEncodingStrategy = .base64
+            dataEncodingStrategy: DataEncodingStrategy = .base64,
+            writeOptions: YYJSONWriteOptions = .default
         ) {
             self.doc = doc
             self.value = value
@@ -150,6 +153,7 @@ import Foundation
             self.userInfo = userInfo
             self.dateEncodingStrategy = dateEncodingStrategy
             self.dataEncodingStrategy = dataEncodingStrategy
+            self.writeOptions = writeOptions
         }
 
         func container<Key>(keyedBy type: Key.Type) -> KeyedEncodingContainer<Key> where Key: CodingKey {
@@ -188,6 +192,15 @@ import Foundation
                 dataEncodingStrategy: dataEncodingStrategy
             )
         }
+
+        func numberValue(_ value: Double) -> UnsafeMutablePointer<yyjson_mut_val> {
+            #if !YYJSON_DISABLE_NON_STANDARD
+                if !value.isFinite && writeOptions.contains(.infAndNaNAsNull) {
+                    return yyjson_mut_null(doc)
+                }
+            #endif
+            return yyjson_mut_real(doc, value)
+        }
     }
 
     // MARK: - Encoding Containers
@@ -248,7 +261,7 @@ import Foundation
 
         mutating func encode(_ value: Double, forKey key: Key) throws {
             guard let obj = self.value else { return }
-            let numVal = yyjson_mut_real(doc, value)
+            let numVal = encoder.numberValue(value)
             let keyVal = yyFromString(key.stringValue, in: doc)
             _ = yyjson_mut_obj_put(obj, keyVal, numVal)
         }
@@ -332,7 +345,8 @@ import Foundation
                 codingPath: codingPath + [key],
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
             let encodedValue = try encodeValue(value, using: encoder)
             let keyVal = yyFromString(key.stringValue, in: doc)
@@ -349,7 +363,8 @@ import Foundation
                     codingPath: codingPath + [key],
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 return encoder.container(keyedBy: type)
             }
@@ -362,7 +377,8 @@ import Foundation
                 codingPath: codingPath + [key],
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
             return encoder.container(keyedBy: type)
         }
@@ -375,7 +391,8 @@ import Foundation
                     codingPath: codingPath + [key],
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 return nestedEncoder.unkeyedContainer()
             }
@@ -388,7 +405,8 @@ import Foundation
                 codingPath: codingPath + [key],
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
             return _YYUnkeyedEncodingContainer(
                 doc: doc,
@@ -408,7 +426,8 @@ import Foundation
                 codingPath: codingPath,
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
         }
 
@@ -420,7 +439,8 @@ import Foundation
                     codingPath: codingPath + [key],
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
             }
             let nestedObj = yyjson_mut_obj(doc)
@@ -432,7 +452,8 @@ import Foundation
                 codingPath: codingPath + [key],
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
         }
 
@@ -447,7 +468,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try date.encode(to: encoder)
                 guard let val = encoder.value else {
@@ -481,7 +503,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try closure(date, encoder)
                 guard let val = encoder.value else {
@@ -509,7 +532,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try data.encode(to: encoder)
                 guard let val = encoder.value else {
@@ -527,7 +551,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try closure(data, encoder)
                 guard let val = encoder.value else {
@@ -612,7 +637,7 @@ import Foundation
 
         mutating func encode(_ value: Double) throws {
             guard let arr = self.value else { return }
-            let numVal = yyjson_mut_real(doc, value)
+            let numVal = encoder.numberValue(value)
             _ = yyjson_mut_arr_append(arr, numVal)
         }
 
@@ -689,7 +714,8 @@ import Foundation
                 codingPath: codingPath + [AnyCodingKey(index: count)],
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
             let encodedValue = try encodeValue(value, using: encoder)
             _ = yyjson_mut_arr_append(arr, encodedValue)
@@ -708,7 +734,8 @@ import Foundation
                 codingPath: codingPath + [AnyCodingKey(index: count)],
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
             return encoder.container(keyedBy: type)
         }
@@ -724,7 +751,8 @@ import Foundation
                 codingPath: codingPath + [AnyCodingKey(index: count)],
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
             return _YYUnkeyedEncodingContainer(
                 doc: doc,
@@ -744,7 +772,8 @@ import Foundation
                 codingPath: codingPath,
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
         }
 
@@ -759,7 +788,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try date.encode(to: encoder)
                 guard let val = encoder.value else {
@@ -793,7 +823,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try closure(date, encoder)
                 guard let val = encoder.value else {
@@ -821,7 +852,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try data.encode(to: encoder)
                 guard let val = encoder.value else {
@@ -839,7 +871,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try closure(data, encoder)
                 guard let val = encoder.value else {
@@ -910,7 +943,7 @@ import Foundation
         }
 
         mutating func encode(_ value: Double) throws {
-            self.value = yyjson_mut_real(doc, value)
+            self.value = encoder.numberValue(value)
             encoder.value = self.value
         }
 
@@ -981,7 +1014,8 @@ import Foundation
                 codingPath: codingPath,
                 userInfo: userInfo,
                 dateEncodingStrategy: dateEncodingStrategy,
-                dataEncodingStrategy: dataEncodingStrategy
+                dataEncodingStrategy: dataEncodingStrategy,
+                writeOptions: encoder.writeOptions
             )
             try value.encode(to: nestedEncoder)
             self.value = nestedEncoder.value
@@ -997,7 +1031,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try date.encode(to: nestedEncoder)
                 guard let val = nestedEncoder.value else {
@@ -1031,7 +1066,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try closure(date, nestedEncoder)
                 guard let val = nestedEncoder.value else {
@@ -1057,7 +1093,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try data.encode(to: nestedEncoder)
                 guard let val = nestedEncoder.value else {
@@ -1075,7 +1112,8 @@ import Foundation
                     codingPath: codingPath,
                     userInfo: userInfo,
                     dateEncodingStrategy: dateEncodingStrategy,
-                    dataEncodingStrategy: dataEncodingStrategy
+                    dataEncodingStrategy: dataEncodingStrategy,
+                    writeOptions: encoder.writeOptions
                 )
                 try closure(data, nestedEncoder)
                 guard let val = nestedEncoder.value else {
diff --git a/Sources/YYJSON/Serialization.swift b/Sources/YYJSON/Serialization.swift
index 62052c9..1e73bc7 100644
--- a/Sources/YYJSON/Serialization.swift
+++ b/Sources/YYJSON/Serialization.swift
@@ -64,6 +64,20 @@ public enum YYJSONSerialization {
 
         /// Add a single newline character `\n` at the end of the JSON.
         public static let newlineAtEnd = WritingOptions(rawValue: 1 << 6)
+
+        #if !YYJSON_DISABLE_NON_STANDARD
+
+            /// Writes infinity and NaN values as `Infinity` and `NaN` literals.
+            ///
+            /// If you set `infAndNaNAsNull`, it takes precedence.
+            public static let allowInfAndNaN = WritingOptions(rawValue: 1 << 7)
+
+            /// Writes infinity and NaN values as `null` literals.
+            ///
+            /// This option takes precedence over `allowInfAndNaN`.
+            public static let infAndNaNAsNull = WritingOptions(rawValue: 1 << 8)
+
+        #endif  // !YYJSON_DISABLE_NON_STANDARD
     }
 
     /// Returns a Foundation object from given JSON data.
@@ -127,8 +141,17 @@ public enum YYJSONSerialization {
             let isTopLevelContainer = obj is NSArray || obj is NSDictionary
             let isFragment = obj is NSString || obj is NSNumber || obj is NSNull
 
+            let allowNonFiniteNumbers: Bool
+            #if !YYJSON_DISABLE_NON_STANDARD
+                allowNonFiniteNumbers =
+                    options.contains(.infAndNaNAsNull)
+                    || options.contains(.allowInfAndNaN)
+            #else
+                allowNonFiniteNumbers = false
+            #endif
+
             if isTopLevelContainer {
-                guard isValidJSONObject(obj) else {
+                guard isValidJSONObject(obj, allowNonFiniteNumbers: allowNonFiniteNumbers) else {
                     throw YYJSONError.invalidData("Invalid JSON object")
                 }
             } else if isFragment {
@@ -166,6 +189,15 @@ public enum YYJSONSerialization {
                 flags |= YYJSON_WRITE_ESCAPE_UNICODE
             }
 
+            #if !YYJSON_DISABLE_NON_STANDARD
+                if options.contains(.allowInfAndNaN) {
+                    flags |= YYJSON_WRITE_ALLOW_INF_AND_NAN
+                }
+                if options.contains(.infAndNaNAsNull) {
+                    flags |= YYJSON_WRITE_INF_AND_NAN_AS_NULL
+                }
+            #endif
+
             // Formatting options
             if options.contains(.newlineAtEnd) {
                 flags |= YYJSON_WRITE_NEWLINE_AT_END
@@ -197,12 +229,22 @@ public enum YYJSONSerialization {
         guard obj is NSArray || obj is NSDictionary else {
             return false
         }
-        return isValidJSONObjectRecursive(obj)
+        return isValidJSONObjectRecursive(obj, allowNonFiniteNumbers: false)
     }
 
     // MARK: - Private Helpers
 
-    private static func isValidJSONObjectRecursive(_ obj: Any) -> Bool {
+    private static func isValidJSONObject(_ obj: Any, allowNonFiniteNumbers: Bool) -> Bool {
+        guard obj is NSArray || obj is NSDictionary else {
+            return false
+        }
+        return isValidJSONObjectRecursive(obj, allowNonFiniteNumbers: allowNonFiniteNumbers)
+    }
+
+    private static func isValidJSONObjectRecursive(
+        _ obj: Any,
+        allowNonFiniteNumbers: Bool
+    ) -> Bool {
         switch obj {
         case let dict as NSDictionary:
             for (key, value) in dict {
@@ -211,11 +253,11 @@ public enum YYJSONSerialization {
                 }
                 if let number = value as? NSNumber {
                     let doubleValue = number.doubleValue
-                    if doubleValue.isNaN || doubleValue.isInfinite {
+                    if !allowNonFiniteNumbers && (doubleValue.isNaN || doubleValue.isInfinite) {
                         return false
                     }
                 }
-                if !isValidJSONObjectRecursive(value) {
+                if !isValidJSONObjectRecursive(value, allowNonFiniteNumbers: allowNonFiniteNumbers) {
                     return false
                 }
             }
@@ -225,11 +267,11 @@ public enum YYJSONSerialization {
             for element in arr {
                 if let number = element as? NSNumber {
                     let doubleValue = number.doubleValue
-                    if doubleValue.isNaN || doubleValue.isInfinite {
+                    if !allowNonFiniteNumbers && (doubleValue.isNaN || doubleValue.isInfinite) {
                         return false
                     }
                 }
-                if !isValidJSONObjectRecursive(element) {
+                if !isValidJSONObjectRecursive(element, allowNonFiniteNumbers: allowNonFiniteNumbers) {
                     return false
                 }
             }
@@ -278,6 +320,14 @@ public enum YYJSONSerialization {
             if options.contains(.newlineAtEnd) {
                 writeOptions.insert(.newlineAtEnd)
             }
+            #if !YYJSON_DISABLE_NON_STANDARD
+                if options.contains(.allowInfAndNaN) {
+                    writeOptions.insert(.allowInfAndNaN)
+                }
+                if options.contains(.infAndNaNAsNull) {
+                    writeOptions.insert(.infAndNaNAsNull)
+                }
+            #endif
 
             return try value.data(options: writeOptions)
         }
@@ -297,6 +347,14 @@ public enum YYJSONSerialization {
             case let num as NSNumber:
                 let doubleValue = num.doubleValue
                 if doubleValue.isNaN || doubleValue.isInfinite {
+                    #if !YYJSON_DISABLE_NON_STANDARD
+                        if options.contains(.infAndNaNAsNull) {
+                            return yyjson_mut_null(doc)
+                        }
+                        if options.contains(.allowInfAndNaN) {
+                            return yyjson_mut_real(doc, doubleValue)
+                        }
+                    #endif
                     throw YYJSONError.invalidData("NaN or Infinity not allowed in JSON")
                 }
 
diff --git a/Tests/YYJSONTests/ConfigurationTests.swift b/Tests/YYJSONTests/ConfigurationTests.swift
index 4c97f42..0d50513 100644
--- a/Tests/YYJSONTests/ConfigurationTests.swift
+++ b/Tests/YYJSONTests/ConfigurationTests.swift
@@ -220,6 +220,33 @@ import Testing
                 #expect(json == "null")
             }
 
+            @Test func allowInfAndNaNNaNOption() throws {
+                var encoder = YYJSONEncoder()
+                encoder.writeOptions = .allowInfAndNaN
+
+                let data = try encoder.encode(Double.nan)
+                let json = String(data: data, encoding: .utf8)!
+                #expect(json.contains("NaN") || json.contains("nan"))
+            }
+
+            @Test func infAndNaNAsNullNaNOption() throws {
+                var encoder = YYJSONEncoder()
+                encoder.writeOptions = .infAndNaNAsNull
+
+                let data = try encoder.encode(Double.nan)
+                let json = String(data: data, encoding: .utf8)!
+                #expect(json == "null")
+            }
+
+            @Test func infAndNaNAsNullOverridesAllowInfAndNaN() throws {
+                var encoder = YYJSONEncoder()
+                encoder.writeOptions = [.allowInfAndNaN, .infAndNaNAsNull]
+
+                let data = try encoder.encode(Double.infinity)
+                let json = String(data: data, encoding: .utf8)!
+                #expect(json == "null")
+            }
+
         #endif  // !YYJSON_DISABLE_NON_STANDARD
 
         @Test func newlineAtEndOption() throws {
diff --git a/Tests/YYJSONTests/SerializationTests.swift b/Tests/YYJSONTests/SerializationTests.swift
index dbeb8dd..db015c0 100644
--- a/Tests/YYJSONTests/SerializationTests.swift
+++ b/Tests/YYJSONTests/SerializationTests.swift
@@ -168,6 +168,59 @@ import Testing
             #expect(json == "[1,2,3,4,5]")
         }
 
+        #if !YYJSON_DISABLE_NON_STANDARD
+
+            @Test func writeAllowsInfAndNaNLiterals() throws {
+                let dict: NSDictionary = [
+                    "inf": Double.infinity,
+                    "nan": Double.nan,
+                ]
+                let data = try YYJSONSerialization.data(
+                    withJSONObject: dict,
+                    options: .allowInfAndNaN
+                )
+                let json = String(data: data, encoding: .utf8)!
+                #expect(json.contains("Infinity") || json.contains("inf"))
+                #expect(json.contains("NaN") || json.contains("nan"))
+            }
+
+            @Test func writeInfAndNaNAsNull() throws {
+                let dict: NSDictionary = [
+                    "inf": Double.infinity,
+                    "nan": Double.nan,
+                ]
+                let data = try YYJSONSerialization.data(
+                    withJSONObject: dict,
+                    options: .infAndNaNAsNull
+                )
+                let json = String(data: data, encoding: .utf8)!
+                #expect(json.contains("\"inf\":null"))
+                #expect(json.contains("\"nan\":null"))
+            }
+
+            @Test func writeInfAndNaNAsNullOverridesAllowInfAndNaN() throws {
+                let dict: NSDictionary = [
+                    "inf": Double.infinity,
+                    "nan": Double.nan,
+                ]
+                let data = try YYJSONSerialization.data(
+                    withJSONObject: dict,
+                    options: [.allowInfAndNaN, .infAndNaNAsNull]
+                )
+                let json = String(data: data, encoding: .utf8)!
+                #expect(json.contains("\"inf\":null"))
+                #expect(json.contains("\"nan\":null"))
+            }
+
+            @Test func writeNonFiniteWithoutOptionThrows() throws {
+                let dict: NSDictionary = ["value": Double.nan]
+                #expect(throws: YYJSONError.self) {
+                    _ = try YYJSONSerialization.data(withJSONObject: dict)
+                }
+            }
+
+        #endif  // !YYJSON_DISABLE_NON_STANDARD
+
         #if !YYJSON_DISABLE_READER
 
             private static func jsonString(