diff --git a/csharp/App/Backend/Controller.cs b/csharp/App/Backend/Controller.cs
index a80045590..832f84dda 100644
--- a/csharp/App/Backend/Controller.cs
+++ b/csharp/App/Backend/Controller.cs
@@ -2639,16 +2639,18 @@ public class Controller : ControllerBase
     private static readonly HashSet<String> AllowedMimeTypes = new(StringComparer.OrdinalIgnoreCase)
     {
         "image/jpeg", "image/png", "image/gif", "image/webp",
-        "application/pdf", "application/x-pdf"
+        "application/pdf", "application/x-pdf",
+        "video/mp4", "video/quicktime", "video/webm"
     };
 
     // Some browsers send generic MIME types — allow them if the file extension is valid
     private static readonly HashSet<String> AllowedExtensions = new(StringComparer.OrdinalIgnoreCase)
     {
-        ".jpg", ".jpeg", ".png", ".gif", ".webp", ".pdf"
+        ".jpg", ".jpeg", ".png", ".gif", ".webp", ".pdf",
+        ".mp4", ".mov", ".webm"
     };
 
-    private const Int64 MaxFileSizeBytes = 25 * 1024 * 1024; // 25 MB
+    private const Int64 MaxFileSizeBytes = 100 * 1024 * 1024; // 100 MB
 
     private static S3Bucket DocumentBucket
     {
@@ -2660,7 +2662,7 @@ public class Controller : ControllerBase
     }
 
     [HttpPost(nameof(UploadDocument))]
-    [RequestSizeLimit(26_214_400)]
+    [RequestSizeLimit(104_857_600)]
     public async Task<ActionResult<Document>> UploadDocument(
         IFormFile file,
         [FromQuery] Int32 scope,
diff --git a/typescript/frontend-marios2/src/components/DocumentList.tsx b/typescript/frontend-marios2/src/components/DocumentList.tsx
index 41f3ad042..9c92b589e 100644
--- a/typescript/frontend-marios2/src/components/DocumentList.tsx
+++ b/typescript/frontend-marios2/src/components/DocumentList.tsx
@@ -13,6 +13,8 @@ import DownloadIcon from '@mui/icons-material/Download';
 import DeleteIcon from '@mui/icons-material/Delete';
 import InsertDriveFileIcon from '@mui/icons-material/InsertDriveFile';
 import PictureAsPdfIcon from '@mui/icons-material/PictureAsPdf';
+import VideocamIcon from '@mui/icons-material/Videocam';
+import PlayCircleOutlineIcon from '@mui/icons-material/PlayCircleOutline';
 import { FormattedMessage } from 'react-intl';
 import axiosConfig from 'src/Resources/axiosConfig';
 
@@ -48,8 +50,13 @@ function isImage(contentType: string): boolean {
   return contentType.startsWith('image/');
 }
 
+function isVideo(contentType: string): boolean {
+  return contentType.startsWith('video/');
+}
+
 function getFileIcon(contentType: string) {
   if (contentType === 'application/pdf') return <PictureAsPdfIcon fontSize="small" color="error" />;
+  if (isVideo(contentType)) return <VideocamIcon fontSize="small" color="primary" />;
   return <InsertDriveFileIcon fontSize="small" />;
 }
 
@@ -63,7 +70,36 @@ function DocumentList({
   const [documents, setDocuments] = useState<DocumentItem[]>([]);
   const [loading, setLoading] = useState(true);
   const [previews, setPreviews] = useState<Record<number, string>>({});
+  const [videoUrls, setVideoUrls] = useState<Record<number, string>>({});
+  const [loadingVideoIds, setLoadingVideoIds] = useState<Set<number>>(new Set());
   const [expandedImage, setExpandedImage] = useState<string | null>(null);
+  const [expandedVideo, setExpandedVideo] = useState<{ url: string; contentType: string } | null>(null);
+
+  const loadVideoBlob = (doc: DocumentItem) => {
+    if (videoUrls[doc.id] || loadingVideoIds.has(doc.id)) return;
+    setLoadingVideoIds((prev) => {
+      const next = new Set(prev);
+      next.add(doc.id);
+      return next;
+    });
+    axiosConfig
+      .get('/DownloadDocument', {
+        params: { id: doc.id },
+        responseType: 'blob'
+      })
+      .then((res) => {
+        const url = window.URL.createObjectURL(new Blob([res.data], { type: doc.contentType }));
+        setVideoUrls((prev) => ({ ...prev, [doc.id]: url }));
+      })
+      .catch(() => {})
+      .finally(() => {
+        setLoadingVideoIds((prev) => {
+          const next = new Set(prev);
+          next.delete(doc.id);
+          return next;
+        });
+      });
+  };
 
   const fetchDocuments = () => {
     setLoading(true);
@@ -104,13 +140,15 @@ function DocumentList({
   useEffect(() => {
     return () => {
       Object.values(previews).forEach((url) => window.URL.revokeObjectURL(url));
+      Object.values(videoUrls).forEach((url) => window.URL.revokeObjectURL(url));
     };
   }, []);
 
   const handleDownload = (doc: DocumentItem) => {
-    if (previews[doc.id]) {
+    const cached = previews[doc.id] || videoUrls[doc.id];
+    if (cached) {
       const link = document.createElement('a');
-      link.href = previews[doc.id];
+      link.href = cached;
       link.setAttribute('download', doc.originalName);
       document.body.appendChild(link);
       link.click();
@@ -196,6 +234,53 @@ function DocumentList({
                 }}
               />
             )}
+            {isVideo(doc.contentType) && (
+              videoUrls[doc.id] ? (
+                <Box
+                  component="video"
+                  controls
+                  src={videoUrls[doc.id]}
+                  onClick={() => setExpandedVideo({ url: videoUrls[doc.id], contentType: doc.contentType })}
+                  sx={{
+                    maxWidth: 240,
+                    maxHeight: 160,
+                    borderRadius: 1,
+                    border: '1px solid',
+                    borderColor: 'divider',
+                    cursor: 'pointer',
+                    backgroundColor: 'common.black'
+                  }}
+                />
+              ) : (
+                <Box
+                  onClick={() => loadVideoBlob(doc)}
+                  sx={{
+                    width: 240,
+                    height: 135,
+                    borderRadius: 1,
+                    border: '1px solid',
+                    borderColor: 'divider',
+                    backgroundColor: 'action.hover',
+                    cursor: loadingVideoIds.has(doc.id) ? 'progress' : 'pointer',
+                    display: 'flex',
+                    alignItems: 'center',
+                    justifyContent: 'center',
+                    flexDirection: 'column',
+                    gap: 0.5,
+                    '&:hover': { opacity: 0.85 }
+                  }}
+                >
+                  <PlayCircleOutlineIcon sx={{ fontSize: 48, color: 'text.secondary' }} />
+                  <Typography variant="caption" color="text.secondary">
+                    {loadingVideoIds.has(doc.id) ? (
+                      <FormattedMessage id="videoLoading" defaultMessage="Loading…" />
+                    ) : (
+                      <FormattedMessage id="videoClickToPlay" defaultMessage="Click to play" />
+                    )}
+                  </Typography>
+                </Box>
+              )
+            )}
           </ListItem>
         ))}
       </List>
@@ -215,6 +300,23 @@ function DocumentList({
           />
         )}
       </Dialog>
+
+      {/* Full-size video preview dialog */}
+      <Dialog
+        open={!!expandedVideo}
+        onClose={() => setExpandedVideo(null)}
+        maxWidth="lg"
+      >
+        {expandedVideo && (
+          <Box
+            component="video"
+            controls
+            autoPlay
+            src={expandedVideo.url}
+            sx={{ maxWidth: '90vw', maxHeight: '90vh', backgroundColor: 'common.black' }}
+          />
+        )}
+      </Dialog>
     </Box>
   );
 }
diff --git a/typescript/frontend-marios2/src/components/FileUploadButton.tsx b/typescript/frontend-marios2/src/components/FileUploadButton.tsx
index 992531db4..f78ea2c7c 100644
--- a/typescript/frontend-marios2/src/components/FileUploadButton.tsx
+++ b/typescript/frontend-marios2/src/components/FileUploadButton.tsx
@@ -7,7 +7,7 @@ import {
   Typography
 } from '@mui/material';
 import AttachFileIcon from '@mui/icons-material/AttachFile';
-import { FormattedMessage } from 'react-intl';
+import { FormattedMessage, useIntl } from 'react-intl';
 import axiosConfig from 'src/Resources/axiosConfig';
 
 const ALLOWED_TYPES = [
@@ -15,9 +15,13 @@ const ALLOWED_TYPES = [
   'image/png',
   'image/gif',
   'image/webp',
-  'application/pdf'
+  'application/pdf',
+  'video/mp4',
+  'video/quicktime',
+  'video/webm'
 ];
-const MAX_FILE_SIZE = 25 * 1024 * 1024; // 25 MB
+const MAX_FILE_SIZE = 100 * 1024 * 1024; // 100 MB
+const MAX_FILE_SIZE_MB = MAX_FILE_SIZE / (1024 * 1024);
 
 export interface UploadedDocument {
   id: number;
@@ -48,6 +52,7 @@ function FileUploadButton({
   onUploaded,
   disabled = false
 }: FileUploadButtonProps) {
+  const intl = useIntl();
   const inputRef = useRef<HTMLInputElement>(null);
   const [uploading, setUploading] = useState(false);
   const [progress, setProgress] = useState(0);
@@ -62,11 +67,21 @@ function FileUploadButton({
     for (let i = 0; i < files.length; i++) {
       const file = files[i];
       if (!ALLOWED_TYPES.includes(file.type)) {
-        setError(`Invalid file type: ${file.name}`);
+        setError(
+          intl.formatMessage(
+            { id: 'attachFileInvalidType', defaultMessage: 'Invalid file type: {name}' },
+            { name: file.name }
+          )
+        );
         return;
       }
       if (file.size > MAX_FILE_SIZE) {
-        setError(`File too large: ${file.name} (max 25 MB)`);
+        setError(
+          intl.formatMessage(
+            { id: 'attachFileTooLarge', defaultMessage: 'File too large: {name} (max {limitMb} MB)' },
+            { name: file.name, limitMb: MAX_FILE_SIZE_MB }
+          )
+        );
         return;
       }
       validFiles.push(file);
diff --git a/typescript/frontend-marios2/src/content/dashboards/Documents/DocumentsTab.tsx b/typescript/frontend-marios2/src/content/dashboards/Documents/DocumentsTab.tsx
index 7d9cc6407..79dc807f6 100644
--- a/typescript/frontend-marios2/src/content/dashboards/Documents/DocumentsTab.tsx
+++ b/typescript/frontend-marios2/src/content/dashboards/Documents/DocumentsTab.tsx
@@ -51,7 +51,7 @@ function DocumentsTab({ installationId }: DocumentsTabProps) {
           <Typography variant="caption" color="text.secondary" sx={{ mt: 2, display: 'block' }}>
             <FormattedMessage
               id="documentsHint"
-              defaultMessage="Accepted formats: JPEG, PNG, GIF, WebP, PDF. Maximum file size: 25 MB."
+              defaultMessage="Accepted formats: JPEG, PNG, GIF, WebP, PDF, MP4, MOV, WebM. Maximum file size: 100 MB."
             />
           </Typography>
         </CardContent>
diff --git a/typescript/frontend-marios2/src/content/dashboards/Tickets/CommentThread.tsx b/typescript/frontend-marios2/src/content/dashboards/Tickets/CommentThread.tsx
index 8802dc883..71dfaef80 100644
--- a/typescript/frontend-marios2/src/content/dashboards/Tickets/CommentThread.tsx
+++ b/typescript/frontend-marios2/src/content/dashboards/Tickets/CommentThread.tsx
@@ -117,8 +117,11 @@ function CommentThread({
     }, 0);
   };
 
-  const ALLOWED_TYPES = ['image/jpeg', 'image/png', 'image/gif', 'image/webp', 'application/pdf'];
-  const MAX_FILE_SIZE = 25 * 1024 * 1024;
+  const ALLOWED_TYPES = [
+    'image/jpeg', 'image/png', 'image/gif', 'image/webp', 'application/pdf',
+    'video/mp4', 'video/quicktime', 'video/webm'
+  ];
+  const MAX_FILE_SIZE = 100 * 1024 * 1024;
 
   const handleFileSelect = (e: React.ChangeEvent<HTMLInputElement>) => {
     const files = e.target.files;
@@ -382,7 +385,7 @@ function CommentThread({
               <input
                 ref={fileInputRef}
                 type="file"
-                accept="image/jpeg,image/png,image/gif,image/webp,application/pdf"
+                accept="image/jpeg,image/png,image/gif,image/webp,application/pdf,video/mp4,video/quicktime,video/webm"
                 multiple
                 style={{ display: 'none' }}
                 onChange={handleFileSelect}
diff --git a/typescript/frontend-marios2/src/lang/de.json b/typescript/frontend-marios2/src/lang/de.json
index c4345f916..c781ba065 100644
--- a/typescript/frontend-marios2/src/lang/de.json
+++ b/typescript/frontend-marios2/src/lang/de.json
@@ -686,8 +686,12 @@
   "sodistorepro": "Sodistore Pro",
   "numberOfInverters": "Anzahl der Wechselrichter",
   "documentsTab": "Dokumente",
-  "documentsHint": "Akzeptierte Formate: JPEG, PNG, GIF, WebP, PDF. Maximale Dateigrösse: 25 MB.",
+  "documentsHint": "Akzeptierte Formate: JPEG, PNG, GIF, WebP, PDF, MP4, MOV, WebM. Maximale Dateigrösse: 100 MB.",
   "attachFiles": "Dateien anhängen",
+  "attachFileInvalidType": "Ungültiger Dateityp: {name}",
+  "attachFileTooLarge": "Datei zu gross: {name} (max. {limitMb} MB)",
+  "videoClickToPlay": "Zum Abspielen klicken",
+  "videoLoading": "Wird geladen…",
   "attachments": "Anhänge",
   "documents": "Dokumente",
   "installationDocuments": "Installationsdokumente",
diff --git a/typescript/frontend-marios2/src/lang/en.json b/typescript/frontend-marios2/src/lang/en.json
index 4fbfac1d9..f871978ba 100644
--- a/typescript/frontend-marios2/src/lang/en.json
+++ b/typescript/frontend-marios2/src/lang/en.json
@@ -434,8 +434,12 @@
   "sodistorepro": "Sodistore Pro",
   "numberOfInverters": "Number of Inverters",
   "documentsTab": "Documents",
-  "documentsHint": "Accepted formats: JPEG, PNG, GIF, WebP, PDF. Maximum file size: 25 MB.",
+  "documentsHint": "Accepted formats: JPEG, PNG, GIF, WebP, PDF, MP4, MOV, WebM. Maximum file size: 100 MB.",
   "attachFiles": "Attach Files",
+  "attachFileInvalidType": "Invalid file type: {name}",
+  "attachFileTooLarge": "File too large: {name} (max {limitMb} MB)",
+  "videoClickToPlay": "Click to play",
+  "videoLoading": "Loading…",
   "attachments": "Attachments",
   "documents": "Documents",
   "installationDocuments": "Installation Documents",
diff --git a/typescript/frontend-marios2/src/lang/fr.json b/typescript/frontend-marios2/src/lang/fr.json
index 114ac199a..7376bacba 100644
--- a/typescript/frontend-marios2/src/lang/fr.json
+++ b/typescript/frontend-marios2/src/lang/fr.json
@@ -686,8 +686,12 @@
   "sodistorepro": "Sodistore Pro",
   "numberOfInverters": "Nombre d'onduleurs",
   "documentsTab": "Documents",
-  "documentsHint": "Formats acceptés : JPEG, PNG, GIF, WebP, PDF. Taille maximale : 25 Mo.",
+  "documentsHint": "Formats acceptés : JPEG, PNG, GIF, WebP, PDF, MP4, MOV, WebM. Taille maximale : 100 Mo.",
   "attachFiles": "Joindre des fichiers",
+  "attachFileInvalidType": "Type de fichier non valide : {name}",
+  "attachFileTooLarge": "Fichier trop volumineux : {name} (max. {limitMb} Mo)",
+  "videoClickToPlay": "Cliquer pour lire",
+  "videoLoading": "Chargement…",
   "attachments": "Pièces jointes",
   "documents": "Documents",
   "installationDocuments": "Documents d'installation",
diff --git a/typescript/frontend-marios2/src/lang/it.json b/typescript/frontend-marios2/src/lang/it.json
index 524bf4e7d..e5790fc18 100644
--- a/typescript/frontend-marios2/src/lang/it.json
+++ b/typescript/frontend-marios2/src/lang/it.json
@@ -686,8 +686,12 @@
   "sodistorepro": "Sodistore Pro",
   "numberOfInverters": "Numero di inverter",
   "documentsTab": "Documenti",
-  "documentsHint": "Formati accettati: JPEG, PNG, GIF, WebP, PDF. Dimensione massima: 25 MB.",
+  "documentsHint": "Formati accettati: JPEG, PNG, GIF, WebP, PDF, MP4, MOV, WebM. Dimensione massima: 100 MB.",
   "attachFiles": "Allega file",
+  "attachFileInvalidType": "Tipo di file non valido: {name}",
+  "attachFileTooLarge": "File troppo grande: {name} (max {limitMb} MB)",
+  "videoClickToPlay": "Clicca per riprodurre",
+  "videoLoading": "Caricamento…",
   "attachments": "Allegati",
   "documents": "Documenti",
   "installationDocuments": "Documenti dell'installazione",