diff --git a/frontend/lib/imageUtils.js b/frontend/lib/imageUtils.js
new file mode 100644
index 0000000..b83d71b
--- /dev/null
+++ b/frontend/lib/imageUtils.js
@@ -0,0 +1,86 @@
+/**
+ * imageUtils.js — Client-side image compression utilities (Fix #573)
+ *
+ * Uses the `browser-image-compression` library to reduce image payload size
+ * before uploading to Cloudinary. This prevents unnecessary bandwidth usage,
+ * speeds up uploads, and reduces Cloudinary storage costs.
+ *
+ * Previously, profile pictures were uploaded as raw, uncompressed base64 strings
+ * (sometimes 5–15 MB). This utility enforces a max size of 1 MB and 1920px dimension.
+ */
+
+import imageCompression from "browser-image-compression";
+
+/**
+ * Compresses a File object and returns a Base64 data URL.
+ * Used for profile picture uploads.
+ *
+ * @param {File} file - The raw image File from an <input type="file">
+ * @param {Object} [options] - Optional override for compression settings
+ * @returns {Promise<string>} - Base64 data URL of the compressed image
+ */
+export const compressImageToBase64 = async (file, options = {}) => {
+    const defaultOptions = {
+        maxSizeMB: 1,              // Max output size: 1 MB
+        maxWidthOrHeight: 1024,    // Max dimension: 1024px (sufficient for avatars)
+        useWebWorker: true,        // Non-blocking compression via Web Worker
+        fileType: "image/webp",    // WebP yields best size/quality ratio
+        initialQuality: 0.8,       // 80% quality — visually lossless for avatars
+        ...options,
+    };
+
+    const compressedFile = await imageCompression(file, defaultOptions);
+    return await fileToBase64(compressedFile);
+};
+
+/**
+ * Compresses a File object and returns a preview Object URL + Base64 string.
+ * Used when you need both a local preview and an uploadable payload.
+ *
+ * @param {File} file - The raw image File
+ * @param {Object} [options] - Optional compression overrides
+ * @returns {Promise<{ previewUrl: string, base64: string }>}
+ */
+export const compressImageForPreviewAndUpload = async (file, options = {}) => {
+    const defaultOptions = {
+        maxSizeMB: 1,
+        maxWidthOrHeight: 1920,   // Higher res for chat images
+        useWebWorker: true,
+        ...options,
+    };
+
+    const compressedFile = await imageCompression(file, defaultOptions);
+    const previewUrl = URL.createObjectURL(compressedFile);
+    const base64 = await fileToBase64(compressedFile);
+    return { previewUrl, base64 };
+};
+
+/**
+ * Reads a File object into a Base64 data URL string.
+ * @param {File} file
+ * @returns {Promise<string>}
+ */
+const fileToBase64 = (file) =>
+    new Promise((resolve, reject) => {
+        const reader = new FileReader();
+        reader.onloadend = () => resolve(reader.result);
+        reader.onerror = () => reject(new Error("Failed to read image file"));
+        reader.readAsDataURL(file);
+    });
+
+/**
+ * Validates that a file is an accepted image type and under the size limit.
+ * @param {File} file
+ * @param {number} [maxMB=5] - Max allowed size in MB before compression
+ * @returns {{ valid: boolean, error?: string }}
+ */
+export const validateImageFile = (file, maxMB = 5) => {
+    const ALLOWED_TYPES = ["image/jpeg", "image/png", "image/webp", "image/gif"];
+    if (!ALLOWED_TYPES.includes(file.type)) {
+        return { valid: false, error: "Unsupported format. Use JPEG, PNG, WebP, or GIF." };
+    }
+    if (file.size > maxMB * 1024 * 1024) {
+        return { valid: false, error: `Image must be under ${maxMB}MB` };
+    }
+    return { valid: true };
+};
diff --git a/frontend/src/store/useAuthStore.js b/frontend/src/store/useAuthStore.js
index 4d66f98..24e6b01 100644
--- a/frontend/src/store/useAuthStore.js
+++ b/frontend/src/store/useAuthStore.js
@@ -2,6 +2,7 @@ import { create } from "zustand";
 import axiosInstance from "../../lib/axios";
 import toast from "react-hot-toast";
 import { connectSocket, disconnectSocket } from "../../lib/socket";
+import { compressImageToBase64, validateImageFile } from "../../lib/imageUtils";
 
 const urlBase64ToUint8Array = (base64String) => {
     const padding = '='.repeat((4 - base64String.length % 4) % 4);
@@ -131,14 +132,42 @@ const useAuthStore = create((set) => ({
         }
     },
 
-    updateProfilePicture: async (base64Image) => {
+    /**
+     * FIX (#573): Compresses the selected image client-side before uploading.
+     * Previously, the raw uncompressed base64 string (up to 15 MB) was sent
+     * directly to the server and then to Cloudinary — wasting bandwidth and
+     * storage. Now the image is compressed to ≤1 MB / 1024px before upload.
+     *
+     * @param {File} imageFile - The raw File object from the file input
+     */
+    updateProfilePicture: async (imageFile) => {
         set({ isLoading: true });
         try {
-            const res = await axiosInstance.put("/auth/update-profile-picture", { profilePicture: base64Image });
+            // Validate file type and size before compression
+            const validation = validateImageFile(imageFile, 10);
+            if (!validation.valid) {
+                toast.error(validation.error);
+                return;
+            }
+
+            toast.loading("Compressing image...", { id: "pic-upload" });
+
+            // Compress client-side to ≤1 MB / 1024px (avatar quality)
+            const compressedBase64 = await compressImageToBase64(imageFile, {
+                maxSizeMB: 1,
+                maxWidthOrHeight: 1024,
+                fileType: "image/webp",
+            });
+
+            toast.loading("Uploading...", { id: "pic-upload" });
+
+            const res = await axiosInstance.put("/auth/update-profile-picture", {
+                profilePicture: compressedBase64,
+            });
             set({ authUser: res.data });
-            toast.success("Profile picture updated!");
+            toast.success("Profile picture updated!", { id: "pic-upload" });
         } catch (error) {
-            toast.error(error.response?.data?.message || "Picture update failed");
+            toast.error(error.response?.data?.message || "Picture update failed", { id: "pic-upload" });
             throw error;
         } finally {
             set({ isLoading: false });