diff --git a/src/api/routes/labeltemplate.js b/src/api/routes/labeltemplate.js
index 5dfc3b1..1864ea0 100644
--- a/src/api/routes/labeltemplate.js
+++ b/src/api/routes/labeltemplate.js
@@ -1,3 +1,4 @@
+import { validateObjects } from 'react-canvas-label-editor';
 import * as db from '../../db/labeltemplate.js';
 import { renderThumb } from '../../services/labelThumb.js';
 import { emit } from '../sse.js';
@@ -29,6 +30,7 @@ function labeltemplateErrorStatus(error) {
     if (error.message?.startsWith('Invalid dpi')) return 400;
     if (error.message?.startsWith('Invalid type')) return 400;
     if (error.message === 'Content required') return 400;
+    if (error.message?.startsWith('Invalid label objects')) return 400;
     return 500;
 }
 
@@ -209,8 +211,13 @@ export function register(app, basePath = '') {
 
         const { name, width, height, dpi, type, content } = req.body ?? {};
 
+        const validation = validateLabelContent(content);
+        if (!validation.valid) {
+            return res.status(400).json({ error: validation.error, ...(validation.errors ? { errors: validation.errors } : {}) });
+        }
+
         try {
-            const thumb = await buildThumb({ width, height, content });
+            const thumb = await buildThumb({ width, height, content, objects: validation.objects });
             const template = await db.create(req.user.id, {
                 name,
                 width,
@@ -242,9 +249,18 @@ export function register(app, basePath = '') {
 
         const { name, width, height, dpi, type, content } = req.body ?? {};
 
+        let validatedObjects;
+        if (content !== undefined) {
+            const validation = validateLabelContent(content);
+            if (!validation.valid) {
+                return res.status(400).json({ error: validation.error, ...(validation.errors ? { errors: validation.errors } : {}) });
+            }
+            validatedObjects = validation.objects;
+        }
+
         try {
             // Re-render thumb whenever content/dimensions are provided
-            const thumb = await buildThumb({ width, height, content });
+            const thumb = await buildThumb({ width, height, content, objects: validatedObjects });
             const template = await db.update(req.user.id, parsedId.id, {
                 name,
                 width,
@@ -445,6 +461,45 @@ function serializeTemplate(template) {
     };
 }
 
+/**
+ * Validates the label template content and its objects.
+ * Expects content to be an object with an `objects` array (or an array of objects).
+ *
+ * @param {any} content
+ * @returns {{ valid: true, objects: Array } | { valid: false, error: string, errors?: string[] }}
+ */
+function validateLabelContent(content) {
+    if (content == null) {
+        return { valid: false, error: 'Content required' };
+    }
+
+    let parsed = content;
+    if (typeof content === 'string') {
+        try {
+            parsed = JSON.parse(content);
+        } catch {
+            return { valid: false, error: 'Invalid JSON in content' };
+        }
+    }
+
+    const objects = Array.isArray(parsed?.objects)
+        ? parsed.objects
+        : Array.isArray(parsed)
+            ? parsed
+            : null;
+
+    if (!objects) {
+        return { valid: false, error: 'content.objects must be an array' };
+    }
+
+    const { valid, errors } = validateObjects(objects);
+    if (!valid) {
+        return { valid: false, error: `Invalid label objects: ${errors.join(', ')}`, errors };
+    }
+
+    return { valid: true, objects };
+}
+
 /**
  * Attempts to render a thumbnail from content + dimensions.
  * Returns null silently if content or dimensions are missing/invalid —
@@ -452,18 +507,20 @@ function serializeTemplate(template) {
  *
  * @returns {Promise<Buffer|null>}
  */
-async function buildThumb({ width, height, content }) {
+async function buildThumb({ width, height, content, objects: passedObjects }) {
     try {
-        if (content == null) return null;
+        if (content == null && passedObjects == null) return null;
         const w = Number(width);
         const h = Number(height);
         if (!Number.isInteger(w) || w <= 0 || !Number.isInteger(h) || h <= 0) return null;
 
-        const objects = Array.isArray(content?.objects)
-            ? content.objects
-            : Array.isArray(content)
-                ? content
-                : [];
+        const objects = passedObjects ?? (
+            Array.isArray(content?.objects)
+                ? content.objects
+                : Array.isArray(content)
+                    ? content
+                    : []
+        );
 
         return await renderThumb({ width: w, height: h, objects });
     } catch {
@@ -471,3 +528,4 @@ async function buildThumb({ width, height, content }) {
         return null;
     }
 }
+