diff --git a/src/components/ui/CopyButton.tsx b/src/components/ui/CopyButton.tsx
index e7325e3..65ba083 100644
--- a/src/components/ui/CopyButton.tsx
+++ b/src/components/ui/CopyButton.tsx
@@ -1,6 +1,7 @@
 import { useState } from 'react';
 import { Check, Copy } from 'lucide-react';
 import { Button } from './Button';
+import { useUi } from '@/i18n/shared';
 
 interface CopyButtonProps {
   value: string;
@@ -8,7 +9,8 @@ interface CopyButtonProps {
   disabled?: boolean;
 }
 
-export function CopyButton({ value, label = 'Copy', disabled }: CopyButtonProps) {
+export function CopyButton({ value, label, disabled }: CopyButtonProps) {
+  const ui = useUi();
   const [copied, setCopied] = useState(false);
 
   const handleCopy = async () => {
@@ -25,7 +27,7 @@ export function CopyButton({ value, label = 'Copy', disabled }: CopyButtonProps)
   return (
     <Button variant="secondary" onClick={handleCopy} disabled={disabled || !value}>
       {copied ? <Check className="w-4 h-4" /> : <Copy className="w-4 h-4" />}
-      {copied ? 'Copied' : label}
+      {copied ? ui.copied : (label ?? ui.copy)}
     </Button>
   );
 }
diff --git a/src/components/ui/CopyImageButton.tsx b/src/components/ui/CopyImageButton.tsx
index b3af9f5..0d22696 100644
--- a/src/components/ui/CopyImageButton.tsx
+++ b/src/components/ui/CopyImageButton.tsx
@@ -1,6 +1,7 @@
 import { useEffect, useState } from 'react';
 import { Check, Copy } from 'lucide-react';
 import { clipboardService } from '@/services/clipboard.service';
+import { useUi } from '@/i18n/shared';
 import { Button } from './Button';
 
 interface CopyImageButtonProps {
@@ -11,6 +12,7 @@ interface CopyImageButtonProps {
 
 /** Copies an image to the clipboard, with brief "Copied" / error feedback. */
 export function CopyImageButton({ blob, disabled }: CopyImageButtonProps) {
+  const ui = useUi();
   const [state, setState] = useState<'idle' | 'copied' | 'error'>('idle');
   // Only decide support after mount so SSR and the first client render match
   // (clipboardService.supported is false on the server, true in the browser).
@@ -35,7 +37,7 @@ export function CopyImageButton({ blob, disabled }: CopyImageButtonProps) {
   return (
     <Button variant="secondary" onClick={handleCopy} disabled={disabled || !blob}>
       {state === 'copied' ? <Check className="h-4 w-4" /> : <Copy className="h-4 w-4" />}
-      {state === 'copied' ? 'Copied' : state === 'error' ? 'Copy failed' : 'Copy image'}
+      {state === 'copied' ? ui.copied : state === 'error' ? ui.copyFailed : ui.copyImage}
     </Button>
   );
 }
diff --git a/src/components/ui/DownloadTextButton.tsx b/src/components/ui/DownloadTextButton.tsx
index 99a3e79..3ce1dd0 100644
--- a/src/components/ui/DownloadTextButton.tsx
+++ b/src/components/ui/DownloadTextButton.tsx
@@ -1,5 +1,6 @@
 import { Download } from 'lucide-react';
 import { downloadService } from '@/services/download';
+import { useUi } from '@/i18n/shared';
 import { Button } from './Button';
 
 interface DownloadTextButtonProps {
@@ -10,12 +11,13 @@ interface DownloadTextButtonProps {
 }
 
 /** Download a string as a file (client-side, via the shared download service). */
-export function DownloadTextButton({ text, filename, mime = 'text/plain;charset=utf-8', label = 'Download' }: DownloadTextButtonProps) {
+export function DownloadTextButton({ text, filename, mime = 'text/plain;charset=utf-8', label }: DownloadTextButtonProps) {
+  const ui = useUi();
   const onClick = () => downloadService.download(new Blob([text], { type: mime }), filename);
   return (
     <Button variant="secondary" onClick={onClick} disabled={!text}>
       <Download className="h-4 w-4" />
-      {label}
+      {label ?? ui.download}
     </Button>
   );
 }
diff --git a/src/components/ui/Dropzone.tsx b/src/components/ui/Dropzone.tsx
index 8fe4de7..406980a 100644
--- a/src/components/ui/Dropzone.tsx
+++ b/src/components/ui/Dropzone.tsx
@@ -1,4 +1,5 @@
 import { useCallback, useState } from 'react';
+import { useUi } from '@/i18n/shared';
 
 export interface DropzoneProps {
   onDrop: (files: File[]) => void | Promise<void>;
@@ -8,6 +9,7 @@ export interface DropzoneProps {
 }
 
 export function Dropzone({ onDrop, accept, multiple = true, children }: DropzoneProps) {
+  const ui = useUi();
   const [isDragging, setIsDragging] = useState(false);
 
   const handleDragOver = useCallback((e: React.DragEvent) => {
@@ -41,7 +43,7 @@ export function Dropzone({ onDrop, accept, multiple = true, children }: Dropzone
       className={`block cursor-pointer border-[3px] border-dashed p-8 text-center transition-all ${isDragging ? 'border-accent bg-accent/10 shadow-brutal' : 'border-border hover:shadow-brutal'}`}
     >
       <input type="file" id="file-input" accept={accept} multiple={multiple} onChange={handleFileInput} className="hidden" />
-      {children || <p>Drop files here or click to browse</p>}
+      {children || <p>{ui.dropzone}</p>}
     </label>
   );
 }
diff --git a/src/components/ui/EditInAnnotatorButton.tsx b/src/components/ui/EditInAnnotatorButton.tsx
index e3d53c0..fd5424a 100644
--- a/src/components/ui/EditInAnnotatorButton.tsx
+++ b/src/components/ui/EditInAnnotatorButton.tsx
@@ -1,5 +1,6 @@
 import { PenTool } from 'lucide-react';
 import { sendImageToAnnotator } from '@/services/handoff';
+import { useUi } from '@/i18n/shared';
 import { Button } from './Button';
 
 interface EditInAnnotatorButtonProps {
@@ -11,6 +12,7 @@ interface EditInAnnotatorButtonProps {
 
 /** Opens the Image Annotator pre-loaded with this image (via IndexedDB handoff). */
 export function EditInAnnotatorButton({ blob, filename = 'image.png', disabled }: EditInAnnotatorButtonProps) {
+  const ui = useUi();
   const handleClick = async () => {
     if (!blob) return;
     const resolved = typeof blob === 'function' ? await blob() : blob;
@@ -20,7 +22,7 @@ export function EditInAnnotatorButton({ blob, filename = 'image.png', disabled }
   return (
     <Button variant="secondary" onClick={handleClick} disabled={disabled || !blob}>
       <PenTool className="h-4 w-4" />
-      Edit in Annotator
+      {ui.editAnnotator}
     </Button>
   );
 }
diff --git a/src/components/ui/ImageResult.tsx b/src/components/ui/ImageResult.tsx
index 08823a8..3affaae 100644
--- a/src/components/ui/ImageResult.tsx
+++ b/src/components/ui/ImageResult.tsx
@@ -1,5 +1,6 @@
 import { useEffect, useState } from 'react';
 import { ResultActions } from './ResultActions';
+import { useUi } from '@/i18n/shared';
 import { formatBytes } from '@/tools/image/canvas.lib';
 
 interface ImageResultProps {
@@ -11,6 +12,7 @@ interface ImageResultProps {
 
 /** Shows an image result: preview, output size (and % change), download. */
 export function ImageResult({ blob, filename, originalSize }: ImageResultProps) {
+  const ui = useUi();
   const [url, setUrl] = useState('');
 
   useEffect(() => {
@@ -25,7 +27,7 @@ export function ImageResult({ blob, filename, originalSize }: ImageResultProps)
   return (
     <div className="space-y-2">
       <div className="flex flex-wrap items-center gap-3 text-sm">
-        <span className="font-bold uppercase tracking-wide text-muted-foreground">Result</span>
+        <span className="font-bold uppercase tracking-wide text-muted-foreground">{ui.result}</span>
         <span className="font-mono">{formatBytes(blob.size)}</span>
         {reduction !== null && (
           <span
@@ -35,14 +37,14 @@ export function ImageResult({ blob, filename, originalSize }: ImageResultProps)
                 : 'font-bold text-red-600 dark:text-red-400'
             }
           >
-            {reduction >= 0 ? `−${reduction}% smaller` : `+${-reduction}% larger`}
+            {reduction >= 0 ? `−${reduction}% ${ui.smaller}` : `+${-reduction}% ${ui.larger}`}
           </span>
         )}
       </div>
       {url && (
         <img
           src={url}
-          alt="Result preview"
+          alt={ui.resultAlt}
           className="max-h-[70vh] w-auto border-2 border-border bg-white"
         />
       )}
diff --git a/src/components/ui/LoadFileButton.tsx b/src/components/ui/LoadFileButton.tsx
index 82c7e66..7927099 100644
--- a/src/components/ui/LoadFileButton.tsx
+++ b/src/components/ui/LoadFileButton.tsx
@@ -1,5 +1,6 @@
 import { useRef } from 'react';
 import { FileUp } from 'lucide-react';
+import { useUi } from '@/i18n/shared';
 import { Button } from './Button';
 
 interface LoadFileButtonProps {
@@ -11,7 +12,8 @@ interface LoadFileButtonProps {
 }
 
 /** A small button that reads a text file from disk and hands back its contents. */
-export function LoadFileButton({ onLoad, accept, label = 'Load file' }: LoadFileButtonProps) {
+export function LoadFileButton({ onLoad, accept, label }: LoadFileButtonProps) {
+  const ui = useUi();
   const ref = useRef<HTMLInputElement>(null);
 
   const handle = async (e: React.ChangeEvent<HTMLInputElement>) => {
@@ -25,7 +27,7 @@ export function LoadFileButton({ onLoad, accept, label = 'Load file' }: LoadFile
     <>
       <Button variant="secondary" onClick={() => ref.current?.click()}>
         <FileUp className="h-4 w-4" />
-        {label}
+        {label ?? ui.loadFile}
       </Button>
       <input ref={ref} type="file" accept={accept} onChange={handle} className="hidden" />
     </>
diff --git a/src/components/ui/ResultActions.tsx b/src/components/ui/ResultActions.tsx
index c04b94e..62c4e2a 100644
--- a/src/components/ui/ResultActions.tsx
+++ b/src/components/ui/ResultActions.tsx
@@ -1,5 +1,6 @@
 import { Download } from 'lucide-react';
 import { downloadService } from '@/services/download';
+import { useUi } from '@/i18n/shared';
 import { Button } from './Button';
 import { CopyImageButton } from './CopyImageButton';
 import { EditInAnnotatorButton } from './EditInAnnotatorButton';
@@ -11,6 +12,7 @@ export interface ResultActionsProps {
 }
 
 export function ResultActions({ blob, filename, disabled }: ResultActionsProps) {
+  const ui = useUi();
   const handleDownload = async () => {
     if (!blob) return;
     await downloadService.download(blob, filename);
@@ -22,7 +24,7 @@ export function ResultActions({ blob, filename, disabled }: ResultActionsProps)
     <div className="flex flex-wrap gap-2">
       <Button onClick={handleDownload} disabled={disabled || !blob}>
         <Download className="h-4 w-4" />
-        Download {filename}
+        {ui.download} {filename}
       </Button>
       {isImage && <CopyImageButton blob={blob} disabled={disabled} />}
       {isImage && <EditInAnnotatorButton blob={blob} filename={filename} disabled={disabled} />}
diff --git a/src/i18n/shared.ts b/src/i18n/shared.ts
new file mode 100644
index 0000000..febcddf
--- /dev/null
+++ b/src/i18n/shared.ts
@@ -0,0 +1,39 @@
+import { useEffect, useState } from 'react';
+import type { Lang } from './config';
+
+/**
+ * Client-side current-locale hook for shared components that aren't passed a `lang`
+ * prop. Reads the URL (/id/… → 'id') and re-checks on every view-transition
+ * navigation. SSR returns 'en'; it settles to the real locale on hydration.
+ */
+export function useLang(): Lang {
+  const [lang, setLang] = useState<Lang>('en');
+  useEffect(() => {
+    const detect = () => setLang(/^\/id(\/|$)/.test(location.pathname) ? 'id' : 'en');
+    detect();
+    document.addEventListener('astro:page-load', detect);
+    return () => document.removeEventListener('astro:page-load', detect);
+  }, []);
+  return lang;
+}
+
+/** Common strings shared across UI components (Copy, Download, Dropzone, …). */
+const SHARED = {
+  en: {
+    copy: 'Copy', copied: 'Copied', copyImage: 'Copy image', copyFailed: 'Copy failed',
+    download: 'Download', loadFile: 'Load file', editAnnotator: 'Edit in Annotator',
+    dropzone: 'Drop files here or click to browse', result: 'Result', resultAlt: 'Result preview',
+    smaller: 'smaller', larger: 'larger',
+  },
+  id: {
+    copy: 'Salin', copied: 'Tersalin', copyImage: 'Salin gambar', copyFailed: 'Gagal menyalin',
+    download: 'Unduh', loadFile: 'Muat file', editAnnotator: 'Edit di Anotator',
+    dropzone: 'Letakkan file di sini atau klik untuk menelusuri', result: 'Hasil', resultAlt: 'Pratinjau hasil',
+    smaller: 'lebih kecil', larger: 'lebih besar',
+  },
+} satisfies Record<Lang, Record<string, string>>;
+
+/** Shared UI strings for the current locale. */
+export function useUi() {
+  return SHARED[useLang()];
+}