diff --git a/src/leaf_contour_efd/utils/paths.py b/src/leaf_contour_efd/utils/paths.py
new file mode 100644
index 0000000..370d8f5
--- /dev/null
+++ b/src/leaf_contour_efd/utils/paths.py
@@ -0,0 +1,69 @@
+"""Path utilities for output/export directories."""
+
+from __future__ import annotations
+
+from pathlib import Path
+import sys
+
+from appdirs import user_data_dir
+
+_APP_DIR_NAME = "leaf_contour_efd"
+
+
+def _user_writable_base_dir() -> Path:
+    """Return a user-writable directory for application outputs."""
+    return Path(user_data_dir(_APP_DIR_NAME)).resolve()
+
+
+def _is_writable_dir(path: Path) -> bool:
+    """Return whether ``path`` can be used as a writable directory."""
+    try:
+        path.mkdir(parents=True, exist_ok=True)
+        probe = path / ".write_test"
+        with probe.open("w", encoding="utf-8"):
+            pass
+        probe.unlink(missing_ok=True)
+        return True
+    except OSError:
+        return False
+
+
+def get_output_base_dir() -> Path:
+    """Return the base directory used for writing the ``output`` folder.
+
+    Rules
+    -----
+    - Frozen on all platforms: user-writable application data directory.
+    - Non-frozen: repository/application root when writable, otherwise user data.
+    """
+    fallback = _user_writable_base_dir()
+
+    if getattr(sys, "frozen", False):
+        return fallback
+
+    # Development mode: src/leaf_contour_efd/utils/paths.py -> repo root
+    repo_root = Path(__file__).resolve().parents[3]
+    if _is_writable_dir(repo_root):
+        return repo_root
+    return fallback
+
+
+def get_output_dir(*parts: str) -> Path:
+    """Return an output subdirectory and ensure it exists.
+
+    If directory creation fails in the primary base location, this function
+    transparently falls back to a user-writable directory.
+    """
+    out_dir = get_output_base_dir() / "output"
+    if parts:
+        out_dir = out_dir.joinpath(*parts)
+
+    try:
+        out_dir.mkdir(parents=True, exist_ok=True)
+    except OSError:
+        out_dir = _user_writable_base_dir() / "output"
+        if parts:
+            out_dir = out_dir.joinpath(*parts)
+        out_dir.mkdir(parents=True, exist_ok=True)
+
+    return out_dir
diff --git a/src/leaf_contour_efd/widgets/binarize_image.py b/src/leaf_contour_efd/widgets/binarize_image.py
index b06a599..26afff9 100644
--- a/src/leaf_contour_efd/widgets/binarize_image.py
+++ b/src/leaf_contour_efd/widgets/binarize_image.py
@@ -26,6 +26,7 @@
 from napari.layers import Image
 from napari.utils.colormaps import DirectLabelColormap
 from pathlib import Path
+from leaf_contour_efd.utils.paths import get_output_dir
 
 
 def make_binarize_image_widget(viewer: "napari.Viewer"):
@@ -223,7 +224,7 @@ def binarize_image(
         method: str = "Otsu",
         threshold: int = 128,
         save_check: bool = True,
-        save_dir: Path = Path("./output/binarized_images"),
+        save_dir: Path = get_output_dir("binarized_images"),
     ):
         """
         Run the selected binarization method
diff --git a/src/leaf_contour_efd/widgets/calculate_efd.py b/src/leaf_contour_efd/widgets/calculate_efd.py
index 328dbfd..d627fd3 100644
--- a/src/leaf_contour_efd/widgets/calculate_efd.py
+++ b/src/leaf_contour_efd/widgets/calculate_efd.py
@@ -15,6 +15,7 @@
 import pandas as pd
 from pathlib import Path
 import copy
+from leaf_contour_efd.utils.paths import get_output_dir
 
 
 def close_contour(df_contour: pd.DataFrame) -> np.ndarray:
@@ -391,10 +392,8 @@ def calculate_efd_and_save(payload) -> None:
         # fallback to plain string
         leaf_id = str(leaf_id)
 
-    output_dir_ef = Path("output/coefficients_efd")
-    output_dir_ef_normalized = Path("output/coefficients_efd_normalized")
-    output_dir_ef.mkdir(parents=True, exist_ok=True)
-    output_dir_ef_normalized.mkdir(parents=True, exist_ok=True)
+    output_dir_ef = get_output_dir("coefficients_efd")
+    output_dir_ef_normalized = get_output_dir("coefficients_efd_normalized")
     ef_file = output_dir_ef / f"{id}_{leaf_id}.csv"
     ef_normalized_file = output_dir_ef_normalized / f"{id}_{leaf_id}.csv"
     df_ef.to_csv(ef_file, index=False)
diff --git a/src/leaf_contour_efd/widgets/clear_viewer.py b/src/leaf_contour_efd/widgets/clear_viewer.py
index 6d8f1a3..be522cd 100644
--- a/src/leaf_contour_efd/widgets/clear_viewer.py
+++ b/src/leaf_contour_efd/widgets/clear_viewer.py
@@ -24,6 +24,7 @@
 from typing import Sequence
 
 from qtpy.QtCore import QTimer
+from leaf_contour_efd.utils.paths import get_output_dir
 
 
 def _clear_except_async(viewer, keep_names: set[str], on_done=None):
@@ -151,7 +152,7 @@ def _get_base_image_id() -> str:
 
     # ---- create FileEdit with dynamic default path ----
     default_image_id = _get_base_image_id()
-    default_dir = Path("output/rois")
+    default_dir = get_output_dir("rois")
     # default_dir.mkdir(parents=True, exist_ok=True)
     default_path = default_dir / f"{default_image_id}.png"
 
diff --git a/src/leaf_contour_efd/widgets/crop_rectangle.py b/src/leaf_contour_efd/widgets/crop_rectangle.py
index ad68591..35058cc 100644
--- a/src/leaf_contour_efd/widgets/crop_rectangle.py
+++ b/src/leaf_contour_efd/widgets/crop_rectangle.py
@@ -26,6 +26,7 @@
 from pathlib import Path
 import napari
 from qtpy.QtCore import QTimer
+from leaf_contour_efd.utils.paths import get_output_dir
 
 COLOR_CYCLE = ["#FF4B00", "#005AFF"]  # base(orange), tip(blue)
 LABELS = ("base", "tip")
@@ -243,7 +244,7 @@ def _apply():
     def add_roi(
         roi_index: int = 1,
         save_cropped: bool = True,
-        save_dir: str = "output/cropped_images",
+        save_dir: Path = get_output_dir("cropped_images"),
     ):
         """Add a cropped ROI image and its landmark layer."""
         ROIs_layer = viewer.layers["ROIs"]
diff --git a/src/leaf_contour_efd/widgets/extract_contour.py b/src/leaf_contour_efd/widgets/extract_contour.py
index c86a02f..cfdc3b5 100644
--- a/src/leaf_contour_efd/widgets/extract_contour.py
+++ b/src/leaf_contour_efd/widgets/extract_contour.py
@@ -29,6 +29,7 @@
 from datetime import datetime
 from napari.utils.colormaps import DirectLabelColormap
 from qtpy.QtCore import QTimer
+from leaf_contour_efd.utils.paths import get_output_dir
 
 
 def make_extract_contour_widget(viewer: "napari.Viewer"):
@@ -76,9 +77,9 @@ def make_extract_contour_widget(viewer: "napari.Viewer"):
         call_button="Extract Contour",
     )
     def extract_contour(
-        folder_csv=Path("./output/contour"),
-        folder_final_mask=Path("./output/binarized_image_final"),
-        folder_blob_mask=Path("./output/contour_image"),
+        folder_csv=Path(get_output_dir("contour")),
+        folder_final_mask=Path(get_output_dir("binarized_image_final")),
+        folder_blob_mask=Path(get_output_dir("contour_image")),
         save_final_mask=True,
         save_blob_mask=True,
     ):
diff --git a/src/leaf_contour_efd/widgets/rotate_image.py b/src/leaf_contour_efd/widgets/rotate_image.py
index be8b2ff..608eed1 100644
--- a/src/leaf_contour_efd/widgets/rotate_image.py
+++ b/src/leaf_contour_efd/widgets/rotate_image.py
@@ -27,6 +27,7 @@
 from pathlib import Path
 from numbers import Integral
 import copy
+from leaf_contour_efd.utils.paths import get_output_dir
 
 
 # -------------------------------------------------------------------------
@@ -289,7 +290,7 @@ def make_points_metadata_widget(
     def points_metadata_widget(
         viewer: "napari.Viewer",
         save_rotated: bool = True,
-        save_dir: str = "output/rotated_images",
+        save_dir: Path = get_output_dir("rotated_images"),
     ) -> dict[str, Any]:
         """Rotate the image corresponding to the current Points layer."""
         try: