diff --git a/lib/src/models/yust_image.dart b/lib/src/models/yust_image.dart
index 8bd35a4d..83b5905d 100644
--- a/lib/src/models/yust_image.dart
+++ b/lib/src/models/yust_image.dart
@@ -76,6 +76,16 @@ class YustImage extends YustFile {
           : null;
   }
 
+  /// Allowed file extensions for image uploads.
+  static const List<String> allowedExtensions = [
+    'jpg',
+    'jpeg',
+    'png',
+    'gif',
+    'tiff',
+    'heic',
+  ];
+
   /// Type identifier for this class
   ///
   /// Used for local caching on mobile devices
diff --git a/lib/src/util/yust_file_validation_options.dart b/lib/src/util/yust_file_validation_options.dart
new file mode 100644
index 00000000..024d3641
--- /dev/null
+++ b/lib/src/util/yust_file_validation_options.dart
@@ -0,0 +1,174 @@
+import '../models/yust_file.dart';
+import 'yust_exception.dart';
+
+/// Options for validating files before upload.
+///
+/// Used by file/image pickers and share intent handling.
+class YustFileValidationOptions {
+  final num numberOfFiles;
+  final bool overwriteSingleFile;
+  final num? maximumFileSizeInKiB;
+  final List<String>? allowedExtensions;
+
+  const YustFileValidationOptions({
+    this.numberOfFiles = 1,
+    this.overwriteSingleFile = false,
+    this.maximumFileSizeInKiB,
+    this.allowedExtensions,
+  });
+
+  /// Validates a new file against all constraints.
+  ///
+  /// Throws typed [YustFileValidationException] subclasses on failure.
+  /// [newFile] is the file to validate.
+  /// [existingFiles] is the list of files already present.
+  /// [newFileSizeInKiB] is the size of the new file in KiB. If not provided,
+  /// the size is calculated from [newFile.bytes] or [newFile.file].
+  void validateFile({
+    required YustFile newFile,
+    required List<YustFile> existingFiles,
+    int? newFileSizeInKiB,
+  }) {
+    _checkFileCount(existingFiles);
+    _checkFileExtension(newFile);
+    _checkFileSize(newFile, newFileSizeInKiB);
+    _checkExistingFileNames(newFile, existingFiles);
+  }
+
+  void _checkFileCount(List<YustFile> existingFiles) {
+    if (!overwriteSingleFile && existingFiles.length >= numberOfFiles) {
+      throw YustFileLimitExceededException(
+        'File limit of $numberOfFiles reached.',
+        limit: numberOfFiles,
+      );
+    }
+
+    if (overwriteSingleFile && existingFiles.length > 1) {
+      throw YustFileLimitExceededException(
+        'File limit of $numberOfFiles reached.',
+        limit: numberOfFiles,
+      );
+    }
+
+    if (overwriteSingleFile && existingFiles.isNotEmpty) {
+      throw YustFileOverwriteRequiredException(
+        'A file already exists and will be overwritten.',
+        existingFile: existingFiles.first,
+      );
+    }
+  }
+
+  void _checkFileExtension(YustFile newFile) {
+    if (allowedExtensions == null || allowedExtensions!.isEmpty) return;
+
+    final extension = newFile.getFilenameExtension().toLowerCase();
+    if (!allowedExtensions!.contains(extension)) {
+      throw YustFileExtensionNotAllowedException(
+        'File extension "$extension" is not allowed.',
+        extension: extension,
+        allowedExtensions: allowedExtensions!,
+      );
+    }
+  }
+
+  void _checkFileSize(YustFile newFile, int? newFileSizeInKiB) {
+    if (maximumFileSizeInKiB == null) return;
+
+    final int fileSizeInKiB;
+    if (newFileSizeInKiB != null) {
+      fileSizeInKiB = newFileSizeInKiB;
+    } else if (newFile.bytes != null) {
+      fileSizeInKiB = newFile.bytes!.length ~/ 1024;
+    } else if (newFile.file != null) {
+      fileSizeInKiB = newFile.file!.lengthSync() ~/ 1024;
+    } else {
+      return;
+    }
+
+    if (fileSizeInKiB > maximumFileSizeInKiB!) {
+      throw YustFileSizeExceededException(
+        'File "${newFile.name}" exceeds the maximum size of $maximumFileSizeInKiB KiB.',
+        fileSizeInKiB: fileSizeInKiB,
+        maximumFileSizeInKiB: maximumFileSizeInKiB!,
+      );
+    }
+  }
+
+  void _checkExistingFileNames(
+    YustFile newFile,
+    List<YustFile> existingFiles,
+  ) {
+    if (existingFiles.any((file) => file.name == newFile.name)) {
+      throw YustFileAlreadyExistsException(
+        'File "${newFile.name}" already exists.',
+        fileName: newFile.name ?? '',
+      );
+    }
+  }
+}
+
+/// Base exception for file validation failures.
+class YustFileValidationException extends YustException {
+  YustFileValidationException(super.message);
+}
+
+/// Thrown when the file size exceeds the maximum allowed size.
+class YustFileSizeExceededException extends YustFileValidationException {
+  final int fileSizeInKiB;
+  final num maximumFileSizeInKiB;
+
+  YustFileSizeExceededException(
+    super.message, {
+    required this.fileSizeInKiB,
+    required this.maximumFileSizeInKiB,
+  });
+}
+
+/// Thrown when the file extension is not in the allowed list.
+class YustFileExtensionNotAllowedException
+    extends YustFileValidationException {
+  final String extension;
+  final List<String> allowedExtensions;
+
+  YustFileExtensionNotAllowedException(
+    super.message, {
+    required this.extension,
+    required this.allowedExtensions,
+  });
+}
+
+/// Thrown when the file limit has been reached.
+class YustFileLimitExceededException extends YustFileValidationException {
+  final num limit;
+
+  YustFileLimitExceededException(
+    super.message, {
+    required this.limit,
+  });
+}
+
+/// Thrown when a file with the same name already exists.
+///
+/// This is a soft validation — callers may choose to confirm with the user
+/// and proceed by deleting the existing file.
+class YustFileAlreadyExistsException extends YustFileValidationException {
+  final String fileName;
+
+  YustFileAlreadyExistsException(
+    super.message, {
+    required this.fileName,
+  });
+}
+
+/// Thrown when overwrite is enabled and an existing file needs to be replaced.
+///
+/// This is a soft validation — callers should confirm with the user before
+/// proceeding to overwrite.
+class YustFileOverwriteRequiredException extends YustFileValidationException {
+  final YustFile existingFile;
+
+  YustFileOverwriteRequiredException(
+    super.message, {
+    required this.existingFile,
+  });
+}
diff --git a/lib/yust.dart b/lib/yust.dart
index 18c1d78f..87b9da41 100644
--- a/lib/yust.dart
+++ b/lib/yust.dart
@@ -40,6 +40,7 @@ export 'src/util/yust_database_statistics.dart'
 export 'src/util/yust_dms_coordinates.dart';
 export 'src/util/yust_exception.dart';
 export 'src/util/yust_field_transform.dart';
+export 'src/util/yust_file_validation_options.dart';
 export 'src/util/yust_helpers.dart';
 export 'src/util/yust_location_appearance.dart';
 export 'src/util/yust_retry_helper.dart';