diff --git a/Sources/FoundationEssentials/Data/Data+Writing.swift b/Sources/FoundationEssentials/Data/Data+Writing.swift
index 4f92cb1a6..ffd8078e8 100644
--- a/Sources/FoundationEssentials/Data/Data+Writing.swift
+++ b/Sources/FoundationEssentials/Data/Data+Writing.swift
@@ -514,6 +514,7 @@ private func writeToFileAux(path inPath: PathOrURL, buffer: UnsafeRawBufferPoint
                 
                 cleanupTemporaryDirectory(at: temporaryDirectoryPath)
                 
+#if !os(WASI) // WASI does not support fchmod for now
                 if let mode {
                     // Try to change the mode if the path has not changed. Do our best, but don't report an error.
 #if FOUNDATION_FRAMEWORK
@@ -537,6 +538,7 @@ private func writeToFileAux(path inPath: PathOrURL, buffer: UnsafeRawBufferPoint
                     fchmod(fd, mode)
 #endif
                 }
+#endif // os(WASI)
             }
         }
     }
diff --git a/Sources/FoundationEssentials/FileManager/FileManager+Files.swift b/Sources/FoundationEssentials/FileManager/FileManager+Files.swift
index 9bb8f0bbb..c4caea035 100644
--- a/Sources/FoundationEssentials/FileManager/FileManager+Files.swift
+++ b/Sources/FoundationEssentials/FileManager/FileManager+Files.swift
@@ -906,6 +906,10 @@ extension _FileManagerImpl {
             let groupID = _readFileAttributePrimitive(attributes[.groupOwnerAccountID], as: UInt.self)
             
             if user != nil || userID != nil || group != nil || groupID != nil {
+                #if os(WASI)
+                // WASI does not have the concept of users or groups
+                throw CocoaError.errorWithFilePath(.featureUnsupported, path)
+                #else
                 // Bias toward userID & groupID - try to prevent round trips to getpwnam if possible.
                 var leaveUnchanged: UInt32 { UInt32(bitPattern: -1) }
                 let rawUserID = userID.flatMap(uid_t.init) ?? user.flatMap(Self._userAccountNameToNumber) ?? leaveUnchanged
@@ -913,6 +917,7 @@ extension _FileManagerImpl {
                 if chown(fileSystemRepresentation, rawUserID, rawGroupID) != 0 {
                     throw CocoaError.errorWithFilePath(path, errno: errno, reading: false)
                 }
+                #endif
             }
             
             try Self._setCatInfoAttributes(attributes, path: path)
diff --git a/Sources/FoundationEssentials/FileManager/FileManager+Utilities.swift b/Sources/FoundationEssentials/FileManager/FileManager+Utilities.swift
index 624b1125f..3d01a2e44 100644
--- a/Sources/FoundationEssentials/FileManager/FileManager+Utilities.swift
+++ b/Sources/FoundationEssentials/FileManager/FileManager+Utilities.swift
@@ -267,7 +267,7 @@ extension _FileManagerImpl {
     }
     #endif
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
     static func _userAccountNameToNumber(_ name: String) -> uid_t? {
         name.withCString { ptr in
             getpwnam(ptr)?.pointee.pw_uid
diff --git a/Sources/FoundationEssentials/FileManager/FileOperations.swift b/Sources/FoundationEssentials/FileManager/FileOperations.swift
index 8e67a771f..130a07ba4 100644
--- a/Sources/FoundationEssentials/FileManager/FileOperations.swift
+++ b/Sources/FoundationEssentials/FileManager/FileOperations.swift
@@ -855,12 +855,14 @@ enum _FileOperations {
         }
         defer { close(dstfd) }
 
+        #if !os(WASI) // WASI doesn't have fchmod for now
         // Set the file permissions using fchmod() instead of when open()ing to avoid umask() issues
         let permissions = fileInfo.st_mode & ~S_IFMT
         guard fchmod(dstfd, permissions) == 0 else {
             try delegate.throwIfNecessary(errno, String(cString: srcPtr), String(cString: dstPtr))
             return
         }
+        #endif
 
         if fileInfo.st_size == 0 {
             // no copying required
diff --git a/Sources/FoundationEssentials/Platform.swift b/Sources/FoundationEssentials/Platform.swift
index 20dc561af..bf2e652d3 100644
--- a/Sources/FoundationEssentials/Platform.swift
+++ b/Sources/FoundationEssentials/Platform.swift
@@ -113,7 +113,7 @@ private let _cachedUGIDs: (uid_t, gid_t) = {
 }()
 #endif
 
-#if !os(Windows)
+#if !os(Windows) && !os(WASI)
 extension Platform {
     private static var ROOT_USER: UInt32 { 0 }
     static func getUGIDs(allowEffectiveRootUID: Bool = true) -> (uid: UInt32, gid: UInt32) {
@@ -174,7 +174,7 @@ extension Platform {
         // FIXME: bionic implements this as `return 0;` and does not expose the
         // function via headers. We should be able to shim this and use the call
         // if it is available.
-#if !os(Android)
+#if !os(Android) && !os(WASI)
         guard issetugid() == 0 else { return nil }
 #endif
         if let value = getenv(name) {
diff --git a/Sources/FoundationEssentials/String/String+Path.swift b/Sources/FoundationEssentials/String/String+Path.swift
index 79bcbfa76..5e42aef4c 100644
--- a/Sources/FoundationEssentials/String/String+Path.swift
+++ b/Sources/FoundationEssentials/String/String+Path.swift
@@ -450,6 +450,7 @@ extension String {
             return envVar.standardizingPath
         }
         
+        #if !os(WASI) // WASI does not have user concept
         // Next, attempt to find the home directory via getpwnam/getpwuid
         var pass: UnsafeMutablePointer<passwd>?
         if let user {
@@ -463,6 +464,7 @@ extension String {
         if let dir = pass?.pointee.pw_dir {
             return String(cString: dir).standardizingPath
         }
+        #endif
         
         // Fallback to HOME for the current user if possible
         if user == nil, let home = getenv("HOME") {