diff --git a/web/static/js/app.js b/web/static/js/app.js
index 8eefc65..46cffc5 100644
--- a/web/static/js/app.js
+++ b/web/static/js/app.js
@@ -14,6 +14,7 @@ document.addEventListener('DOMContentLoaded', () => {
 let sourceType = 'archive';
 let convertFiles = [];
 let isConvertRunning = false;
+let convertDuplicates = [];
 const CONVERT_MAX_FILES_PER_BATCH = 1000;
 let supportedUploadExtensions = null;
 let supportedConvertExtensions = null;
@@ -623,8 +624,16 @@ function initConvertMode() {
         return;
     }
 
-    folderInput.addEventListener('change', () => {
-        convertFiles = Array.from(folderInput.files || []).filter(file => file && file.name);
+    folderInput.addEventListener('change', async () => {
+        const raw = Array.from(folderInput.files || []).filter(file => file && file.name);
+        const summary = document.getElementById('convert-folder-summary');
+        if (summary) {
+            summary.textContent = 'Проверка дубликатов…';
+            summary.className = 'api-connect-status';
+        }
+        const { unique, duplicates } = await deduplicateConvertFiles(raw);
+        convertFiles = unique;
+        convertDuplicates = duplicates;
         renderConvertSummary();
     });
 
@@ -657,7 +666,14 @@ function renderConvertSummary() {
     const batchCount = Math.ceil(supportedFiles.length / CONVERT_MAX_FILES_PER_BATCH);
     const batchesText = batchCount > 1 ? ` Будет ${batchCount} прохода(ов) по ${CONVERT_MAX_FILES_PER_BATCH} файлов.` : '';
 
-    summary.innerHTML = `<strong>${supportedFiles.length}</strong> файлов готовы к конвертации.${previewText ? ` ${previewText}` : ''}${remaining > 0 ? ` и ещё ${remaining}` : ''}.${skippedText}${batchesText}`;
+    let dupText = '';
+    if (convertDuplicates.length > 0) {
+        const names = convertDuplicates.map(d => escapeHtml(d.name)).join(', ');
+        const reasons = convertDuplicates.map(d => d.reason === 'hash' ? 'одинаковое содержимое' : 'одинаковое имя');
+        const uniqueReasons = [...new Set(reasons)].join(', ');
+        dupText = ` <span style="color:#c0392b">⚠ Пропущено дубликатов: ${convertDuplicates.length} (${uniqueReasons}): ${names}.</span>`;
+    }
+    summary.innerHTML = `<strong>${supportedFiles.length}</strong> файлов готовы к конвертации.${previewText ? ` ${previewText}` : ''}${remaining > 0 ? ` и ещё ${remaining}` : ''}.${skippedText}${batchesText}${dupText}`;
     summary.className = 'api-connect-status';
 }
 
@@ -860,6 +876,40 @@ function parseConvertErrorPayload(bodyText) {
     }
 }
 
+async function deduplicateConvertFiles(files) {
+    // First pass: deduplicate by basename
+    const seenNames = new Map(); // name -> index in unique
+    const unique = [];
+    const duplicates = [];
+    for (const file of files) {
+        if (seenNames.has(file.name)) {
+            duplicates.push({ name: file.webkitRelativePath || file.name, reason: 'name' });
+        } else {
+            seenNames.set(file.name, unique.length);
+            unique.push(file);
+        }
+    }
+    // Second pass: deduplicate by SHA-256 hash
+    const seenHashes = new Map(); // hash -> file.name
+    const hashUnique = [];
+    for (const file of unique) {
+        try {
+            const buf = await file.arrayBuffer();
+            const hashBuf = await crypto.subtle.digest('SHA-256', buf);
+            const hash = Array.from(new Uint8Array(hashBuf)).map(b => b.toString(16).padStart(2, '0')).join('');
+            if (seenHashes.has(hash)) {
+                duplicates.push({ name: file.webkitRelativePath || file.name, reason: 'hash' });
+            } else {
+                seenHashes.set(hash, file.name);
+                hashUnique.push(file);
+            }
+        } catch (_) {
+            hashUnique.push(file);
+        }
+    }
+    return { unique: hashUnique, duplicates };
+}
+
 function isSupportedConvertFileName(filename) {
     const name = String(filename || '').trim().toLowerCase();
     if (!name) {