diff --git a/README.md b/README.md
index 3f803816..84b4f229 100644
--- a/README.md
+++ b/README.md
@@ -170,6 +170,13 @@ All scripts located in:
 - Data sync over WiFi/mobile
 - Edit advanced constants
 
+## Trajectory Files
+
+Trajectory recordings are stored as JSON files named `trajectory_<timestamp>.txt`.
+The timestamp follows `dd-MM-yy-HH-mm-ss`. Files are written and read via the
+`TrajectoryIO` helper which converts between the protobuf `Traj.Trajectory`
+and its JSON representation.
+
 ## 🧩 Common Issues & Fixes
 
 | Issue                          | Fix                                                        |
diff --git a/app/src/main/java/com/openpositioning/PositionMe/data/local/FileRepository.java b/app/src/main/java/com/openpositioning/PositionMe/data/local/FileRepository.java
new file mode 100644
index 00000000..069175f2
--- /dev/null
+++ b/app/src/main/java/com/openpositioning/PositionMe/data/local/FileRepository.java
@@ -0,0 +1,63 @@
+package com.openpositioning.PositionMe.data.local;
+
+import android.content.Context;
+import android.os.Build;
+import android.os.Environment;
+import android.util.Log;
+
+import com.openpositioning.PositionMe.Traj;
+
+import java.io.File;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+
+/**
+ * Simple repository for persisting {@link Traj.Trajectory} objects to the app's
+ * private storage. The data is written using {@link TrajectoryIO}.
+ */
+public class FileRepository {
+    private static final String TAG = "FileRepository";
+    private final Context context;
+
+    public FileRepository(Context context) {
+        this.context = context.getApplicationContext();
+    }
+
+    /**
+     * Save the trajectory to the app-specific documents directory.
+     *
+     * @param trajectory trajectory to persist
+     * @return resulting file or {@code null} if failed
+     */
+    public File saveTrajectory(Traj.Trajectory trajectory) {
+        File dir;
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            dir = context.getExternalFilesDir(Environment.DIRECTORY_DOCUMENTS);
+            if (dir == null) {
+                dir = context.getFilesDir();
+            }
+        } else {
+            dir = context.getFilesDir();
+        }
+        if (dir != null && !dir.exists()) {
+            dir.mkdirs();
+        }
+        String time = new SimpleDateFormat("dd-MM-yy-HH-mm-ss").format(new Date());
+        File file = new File(dir, "trajectory_" + time + ".txt");
+        try {
+            TrajectoryIO.writeTrajectory(file, trajectory);
+            Log.i(TAG, "Trajectory written to: " + file.getAbsolutePath());
+            return file;
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to save trajectory", e);
+            return null;
+        }
+    }
+
+    /**
+     * Load a trajectory from a file.
+     */
+    public Traj.Trajectory readTrajectory(File file) throws Exception {
+        return TrajectoryIO.readTrajectory(file);
+    }
+}
diff --git a/app/src/main/java/com/openpositioning/PositionMe/data/local/TrajectoryIO.java b/app/src/main/java/com/openpositioning/PositionMe/data/local/TrajectoryIO.java
new file mode 100644
index 00000000..8c261674
--- /dev/null
+++ b/app/src/main/java/com/openpositioning/PositionMe/data/local/TrajectoryIO.java
@@ -0,0 +1,47 @@
+package com.openpositioning.PositionMe.data.local;
+
+import com.google.protobuf.util.JsonFormat;
+import com.openpositioning.PositionMe.Traj;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+
+/**
+ * Utility class for reading and writing {@link Traj.Trajectory} files.
+ * <p>
+ * The trajectories are stored as JSON text files. Use
+ * {@link #writeTrajectory(File, Traj.Trajectory)} to persist a trajectory and
+ * {@link #readTrajectory(File)} to load it back.
+ */
+public class TrajectoryIO {
+
+    /**
+     * Writes the given trajectory to a file in JSON format.
+     *
+     * @param file destination file
+     * @param traj trajectory to write
+     * @throws IOException if writing fails
+     */
+    public static void writeTrajectory(File file, Traj.Trajectory traj) throws IOException {
+        try (FileWriter writer = new FileWriter(file)) {
+            writer.write(JsonFormat.printer().print(traj));
+            writer.flush();
+        }
+    }
+
+    /**
+     * Reads a trajectory from a JSON file.
+     *
+     * @param file source file
+     * @return parsed trajectory
+     * @throws IOException if reading fails
+     */
+    public static Traj.Trajectory readTrajectory(File file) throws IOException {
+        String json = new String(Files.readAllBytes(file.toPath()));
+        Traj.Trajectory.Builder builder = Traj.Trajectory.newBuilder();
+        JsonFormat.parser().merge(json, builder);
+        return builder.build();
+    }
+}
diff --git a/app/src/main/java/com/openpositioning/PositionMe/data/remote/ServerCommunications.java b/app/src/main/java/com/openpositioning/PositionMe/data/remote/ServerCommunications.java
index 7f7e74b2..f83cac45 100644
--- a/app/src/main/java/com/openpositioning/PositionMe/data/remote/ServerCommunications.java
+++ b/app/src/main/java/com/openpositioning/PositionMe/data/remote/ServerCommunications.java
@@ -28,6 +28,7 @@
 import com.google.protobuf.util.JsonFormat;
 import com.openpositioning.PositionMe.BuildConfig;
 import com.openpositioning.PositionMe.Traj;
+import com.openpositioning.PositionMe.data.local.TrajectoryIO;
 import com.openpositioning.PositionMe.presentation.fragment.FilesFragment;
 import com.openpositioning.PositionMe.presentation.activity.MainActivity;
 import com.openpositioning.PositionMe.sensors.Observable;
@@ -539,10 +540,8 @@ public void onResponse(Call call, Response response) throws IOException {
                     }
 
                     File file = new File(appSpecificDownloads, fileName);
-                    try (FileWriter fileWriter = new FileWriter(file)) {
-                        String receivedTrajectoryString = JsonFormat.printer().print(receivedTrajectory);
-                        fileWriter.write(receivedTrajectoryString);
-                        fileWriter.flush();
+                    try {
+                        TrajectoryIO.writeTrajectory(file, receivedTrajectory);
                         System.err.println("Received trajectory stored in: " + file.getAbsolutePath());
                     } catch (IOException ee) {
                         System.err.println("Trajectory download failed");
diff --git a/app/src/main/java/com/openpositioning/PositionMe/sensors/SensorFusion.java b/app/src/main/java/com/openpositioning/PositionMe/sensors/SensorFusion.java
index 1e14e5eb..ac846779 100644
--- a/app/src/main/java/com/openpositioning/PositionMe/sensors/SensorFusion.java
+++ b/app/src/main/java/com/openpositioning/PositionMe/sensors/SensorFusion.java
@@ -29,6 +29,7 @@
 import com.openpositioning.PositionMe.utils.PdrProcessing;
 import com.openpositioning.PositionMe.data.remote.ServerCommunications;
 import com.openpositioning.PositionMe.Traj;
+import com.openpositioning.PositionMe.data.local.FileRepository;
 import com.openpositioning.PositionMe.presentation.fragment.SettingsFragment;
 import com.openpositioning.PositionMe.domain.EKF;
 
@@ -1322,6 +1323,9 @@ public void setTrajectoryMapFragment(com.openpositioning.PositionMe.presentation
     public void sendTrajectoryToCloud() {
         // Build object
         Traj.Trajectory sentTrajectory = trajectory.build();
+        // Persist locally
+        FileRepository repo = new FileRepository(appContext);
+        repo.saveTrajectory(sentTrajectory);
         // Pass object to communications object
         this.serverCommunications.sendTrajectory(sentTrajectory);
     }