diff --git a/pkl-codegen-kotlin/src/main/kotlin/org/pkl/codegen/kotlin/KotlinCodeGenerator.kt b/pkl-codegen-kotlin/src/main/kotlin/org/pkl/codegen/kotlin/KotlinCodeGenerator.kt
index 6e1de95ea..08efb1780 100644
--- a/pkl-codegen-kotlin/src/main/kotlin/org/pkl/codegen/kotlin/KotlinCodeGenerator.kt
+++ b/pkl-codegen-kotlin/src/main/kotlin/org/pkl/codegen/kotlin/KotlinCodeGenerator.kt
@@ -269,6 +269,11 @@ class KotlinCodeGenerator(
 
     val containRegexProperty = properties.values.any { it.isRegex() }
 
+    fun PClass.Property.isBase64(): Boolean =
+      (this.type as? PType.Class)?.pClass?.info == PClassInfo.Base64
+
+    val containBase64Property = properties.values.any { it.isBase64() }
+
     fun generateConstructor(): FunSpec {
       val builder = FunSpec.constructorBuilder()
       for ((name, property) in allProperties) {
diff --git a/pkl-core/src/main/java/org/pkl/core/stdlib/base/StringNodes.java b/pkl-core/src/main/java/org/pkl/core/stdlib/base/StringNodes.java
index 5035a057e..422279e99 100644
--- a/pkl-core/src/main/java/org/pkl/core/stdlib/base/StringNodes.java
+++ b/pkl-core/src/main/java/org/pkl/core/stdlib/base/StringNodes.java
@@ -19,6 +19,7 @@
 import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
 import com.oracle.truffle.api.dsl.Specialization;
 import com.oracle.truffle.api.nodes.LoopNode;
+import org.apache.commons.codec.binary.Base64;
 import java.nio.charset.StandardCharsets;
 import java.util.*;
 import java.util.regex.*;
@@ -148,6 +149,13 @@ protected boolean eval(String self) {
     }
   }
 
+  public abstract static class isBase64 extends ExternalPropertyNode {
+    @Specialization
+    protected boolean eval(String self) {
+      return Base64.isArrayByteBase64(self.getBytes());
+    }
+  }
+
   public abstract static class chars extends ExternalPropertyNode {
     @Specialization
     @TruffleBoundary
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/api/string.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/api/string.pkl
index c36b0e0c8..1f6ebaeae 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/input/api/string.pkl
+++ b/pkl-core/src/test/files/LanguageSnippetTests/input/api/string.pkl
@@ -57,6 +57,10 @@ facts {
     !str1.endsWith("efx")
   }
 
+  ["isBase64"] {
+    quickBrownFox.base64.isBase64
+  }
+
   ["isRegex"] {
     str1.isRegex
     #"\w*[0-9]"#.isRegex
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/input/api/stringUnicode.pkl b/pkl-core/src/test/files/LanguageSnippetTests/input/api/stringUnicode.pkl
index 9ccfd03b1..57528ebb8 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/input/api/stringUnicode.pkl
+++ b/pkl-core/src/test/files/LanguageSnippetTests/input/api/stringUnicode.pkl
@@ -25,6 +25,10 @@ facts {
     str2.base64.base64Decoded == str2
   }
 
+  ["isBase64"] {
+    str1.isBase64
+  }
+
   ["contains()"] {
     str1.contains(str2)
     str1.contains(str1)
@@ -304,12 +308,12 @@ examples {
     str1.sha1
     str2.sha1
   }
-  
+
   ["sha256"] {
     str1.sha256
     str2.sha256
   }
-  
+
   ["sha256Int"] {
     str1.sha256Int
     str2.sha256Int
@@ -319,7 +323,7 @@ examples {
     str1.md5
     str2.md5
   }
-  
+
   ["base64"] {
     str1.base64
     str2.base64
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/api/string.pcf b/pkl-core/src/test/files/LanguageSnippetTests/output/api/string.pcf
index 643897696..8ae5df5fa 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/output/api/string.pcf
+++ b/pkl-core/src/test/files/LanguageSnippetTests/output/api/string.pcf
@@ -47,6 +47,9 @@ facts {
     true
     true
   }
+  ["isBase64"] {
+    true
+  }
   ["toBoolean()"] {
     true
     true
@@ -175,8 +178,8 @@ examples {
   }
   ["trimStart()"] {
     """
-    abcdefg \t 
-    
+    abcdefg \t
+
     """
   }
   ["trimEnd()"] {
diff --git a/pkl-core/src/test/files/LanguageSnippetTests/output/api/stringUnicode.pcf b/pkl-core/src/test/files/LanguageSnippetTests/output/api/stringUnicode.pcf
index 39fda2628..e98f1b9c1 100644
--- a/pkl-core/src/test/files/LanguageSnippetTests/output/api/stringUnicode.pcf
+++ b/pkl-core/src/test/files/LanguageSnippetTests/output/api/stringUnicode.pcf
@@ -40,6 +40,9 @@ facts {
     true
     true
   }
+  ["isBase64"] {
+    true
+  }
   ["capitalize"] {
     true
     true
@@ -126,8 +129,8 @@ examples {
   }
   ["trimStart()"] {
     """
-    😀😈😍😎😡🤢🤣 \t 
-    
+    😀😈😍😎😡🤢🤣 \t
+
     """
   }
   ["trimEnd()"] {
diff --git a/stdlib/base.pkl b/stdlib/base.pkl
index cffae7cb8..7a8a82b5c 100644
--- a/stdlib/base.pkl
+++ b/stdlib/base.pkl
@@ -1123,6 +1123,9 @@ external class String extends Any {
   /// Tells if this string is a valid regular expression according to [Regex].
   external isRegex: Boolean
 
+  /// Tells if this string is a valid base64 string according to [Base64].
+  external isBase64: Boolean
+
   /// The [MD5](https://en.wikipedia.org/wiki/MD5)
   /// hash of this string's UTF-8 byte sequence
   /// as hexadecimal string.
@@ -1368,7 +1371,7 @@ external class String extends Any {
   external function split(pattern: String|Regex): List<String>
 
   /// Splits this string matches of [pattern], up to [limit] substrings.
-  /// 
+  ///
   /// Returns a [List] with at most [limit] elements.
   /// If the limit has been reached, the last entry will contain the un-split remainder of this string.
   ///
@@ -1379,7 +1382,7 @@ external class String extends Any {
   /// "a.b.c".splitLimit(".", 50) == List("a", "b", "c")
   /// "a.b:c".splitLimit(Regex("[.:]"), 3) == List("a", "b", "c")
   /// ```
-  @Since { version = "0.27.0" } 
+  @Since { version = "0.27.0" }
   external function splitLimit(pattern: String|Regex, limit: Int(this > 0)): List<String>
 
   /// Converts the first character of this string to title case.
@@ -3047,7 +3050,7 @@ external class Set<out Element> extends Collection<Element> {
 
   /// The intersection of this set and [other].
   external function intersect(other: Set): Set<Element>
-  
+
   /// The difference of this set and [other].
   external function difference(other: Set): Set<Element>
 }