diff --git a/frontend/help-ru.html b/frontend/help-ru.html
index e2c01ab..56bf928 100644
--- a/frontend/help-ru.html
+++ b/frontend/help-ru.html
@@ -392,6 +392,7 @@
 		<li><strong>Импорт снимка</strong> &mdash; загружает снимок из JSON-файла.</li>
 		<li>В каждой строке снимка — <strong>Открыть</strong>, <strong>Экспорт</strong> и <strong>Удалить</strong>. <strong>Открыть</strong> показывает все захваченные данные только для чтения (сырой FCI с декодированным FCI, содержимое); редактируется только имя снимка.</li>
 		<li><strong>Проверить снимок карты</strong> в строке профиля выполняет правила профиля на выбранном из списка снимке, без картридера. Отчёт такой же, как при проверке карты; файлы, содержимое которых не было захвачено при сканировании, помечаются как непроверяемые ошибки.</li>
+		<li><strong>Сравнить снимки</strong> сравнивает два снимка без картридера так же, как проверка профиля: выберите <em>эталонный</em> снимок и <em>снимок для проверки</em>, при необходимости включите маску первых 4 байт EF.IMSI/EF.ICCID (включена по умолчанию) и получите такой же отчёт. Файлы, которые есть только в проверяемом снимке, помечаются как лишние. «К списку» возвращает на вкладку «Снимки карт».</li>
 	</ul>
 
 <h3 id="usage-scenarios" class="text-lg font-medium mb-2">5.7 Сценарии использования</h3>
diff --git a/frontend/help.html b/frontend/help.html
index 58a8fb6..b7e640b 100644
--- a/frontend/help.html
+++ b/frontend/help.html
@@ -392,6 +392,7 @@
 		<li><strong>Import snapshot</strong> &mdash; loads a snapshot from a JSON file.</li>
 		<li>Each snapshot row has <strong>Open</strong>, <strong>Export</strong>, and <strong>Delete</strong>. <strong>Open</strong> shows all captured data read-only (raw FCI with the decoded FCI, contents); only the snapshot name is editable.</li>
 		<li><strong>Check card snapshot</strong> on a profile row runs the profile rules against a snapshot you pick from the list, without a card reader. The report is the same as a live check; files whose contents were not captured during the scan are reported as unverifiable errors.</li>
+		<li><strong>Compare snapshots</strong> compares two snapshots offline, exactly like a profile check: pick the <em>master</em> snapshot and the <em>snapshot to check</em>, optionally masking the first 4 bytes of EF.IMSI/EF.ICCID (on by default), and get the same pass/fail report. Files present only in the checked snapshot are reported as extra files. Back to list returns to the Card snapshots tab.</li>
 	</ul>
 
 <h3 id="usage-scenarios" class="text-lg font-medium mb-2">5.7 Usage scenarios</h3>
diff --git a/frontend/index.html b/frontend/index.html
index c58d3e4..521f657 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -830,6 +830,7 @@
 					<div class="flex flex-wrap gap-2 mb-3">
 						<button onclick="snapshotNew()" class="px-2.5 py-1 text-sm rounded bg-blue-600 text-white hover:bg-blue-700" data-l10n="New snapshot">New snapshot</button>
 						<button onclick="document.getElementById('snapshot-import-file').click()" class="px-2.5 py-1 text-sm rounded bg-blue-600 text-white hover:bg-blue-700" data-l10n="Import snapshot">Import snapshot</button>
+						<button onclick="snapshotCompareOpen()" class="px-2.5 py-1 text-sm rounded bg-emerald-600 text-white hover:bg-emerald-700" data-l10n="Compare snapshots">Compare snapshots</button>
 						<input type="file" id="snapshot-import-file" accept=".json,application/json" class="hidden" onchange="snapshotImportFile(this)">
 					</div>
 					<div id="snapshot-list-body"></div>
@@ -975,6 +976,21 @@
 		</div>
 	</div>
 
+	<div id="snapshot-compare-modal" class="fixed inset-0 bg-black/50 z-50 flex items-center justify-center hidden">
+		<div class="bg-white dark:bg-slate-800 rounded-lg p-6 max-w-sm w-full mx-4 max-h-[85vh] overflow-auto">
+			<h3 class="text-lg font-semibold mb-4 text-gray-800 dark:text-slate-200" data-l10n="Compare snapshots">Compare snapshots</h3>
+			<label class="block mb-1 text-xs font-medium text-gray-500 dark:text-slate-400" data-l10n="Master snapshot">Master snapshot</label>
+			<select id="snapshot-compare-master" class="w-full border border-gray-300 dark:border-slate-600 text-sm rounded px-2 py-1.5 dark:bg-slate-800 mb-3"></select>
+			<label class="block mb-1 text-xs font-medium text-gray-500 dark:text-slate-400" data-l10n="Snapshot to check">Snapshot to check</label>
+			<select id="snapshot-compare-check" class="w-full border border-gray-300 dark:border-slate-600 text-sm rounded px-2 py-1.5 dark:bg-slate-800 mb-3"></select>
+			<div id="snapshot-compare-mask" class="space-y-1 mb-3"></div>
+			<div class="flex gap-2 justify-end">
+				<button onclick="document.getElementById('snapshot-compare-modal').classList.add('hidden')" class="px-3 py-1.5 text-xs rounded border border-gray-300 dark:border-slate-600 hover:bg-gray-100 dark:hover:bg-slate-700 text-gray-700 dark:text-slate-300" data-l10n="Cancel">Cancel</button>
+				<button onclick="snapshotCompareRun()" class="px-4 py-1.5 text-xs rounded bg-emerald-600 text-white hover:bg-emerald-700" data-l10n="Compare">Compare</button>
+			</div>
+		</div>
+	</div>
+
 	<div id="stk-menu-panel" class="fixed inset-0 bg-black/50 z-50 flex items-center justify-center hidden">
 		<div class="bg-white dark:bg-slate-800 rounded-lg p-4 max-w-xs w-full max-h-[80vh] flex flex-col">
 			<div class="flex justify-between items-center mb-3">
@@ -7897,7 +7913,7 @@ async function profilerCheck(i) {
 	await profilerRunProfile(p, null, p.name);
 }
 
-async function profilerRunProfile(p, source, title) {
+async function profilerRunProfile(p, source, title, extraResults) {
 	profilerSetView('results');
 	document.getElementById('profiler-results-title').textContent = title;
 	const prog = document.getElementById('profiler-progress');
@@ -7909,6 +7925,7 @@ async function profilerRunProfile(p, source, title) {
 		prog.textContent = t('Checking') + ' ' + (ri + 1) + '/' + p.rules.length + ' — ' + r.path;
 		results.push(await profilerRunRule(r, source));
 	}
+	if (extraResults && extraResults.length) results.push(...extraResults);
 	prog.textContent = '';
 	profilerResults = results;
 	profilerRenderResultsView();
@@ -7937,6 +7954,93 @@ async function profilerCheckSnapshot(i, si) {
 	await profilerRunProfile(p, profilerSnapshotSource(s), p.name + ' — ' + s.name);
 }
 
+function profilerMaskFidForFile(f, maskFids) {
+	if (!maskFids) return null;
+	const seg = (f.path || '').toUpperCase().split('/').pop();
+	if (maskFids.has(seg)) return seg;
+	for (const fid in PROFILER_MASK_PREFIX4_FIDS) {
+		if (maskFids.has(fid) && f.name && PROFILER_MASK_PREFIX4_FIDS[fid] === f.name) return fid;
+	}
+	return null;
+}
+
+function profilerRulesFromSnapshot(master, maskFids) {
+	const rules = [];
+	for (const f of (master.files || [])) {
+		const rule = {
+			type: 'file',
+			path: f.path,
+			name: f.name,
+			fileType: f.fileType,
+			fileSize: f.fileSize,
+			recordLen: f.recordLen,
+			numRecords: f.numRecords,
+			fciMode: 'exact',
+			fciHex: f.fciHex,
+			content: null,
+		};
+		if (f.content) {
+			if (f.content.kind === 'record') {
+				rule.content = { mode: 'exact', kind: 'record', records: f.content.records };
+			} else if (typeof f.content.data === 'string') {
+				rule.content = profilerMaskFidForFile(f, maskFids)
+					? { mode: 'mask', kind: 'transparent', expected: profilerMaskPrefix4(f.content.data) }
+					: { mode: 'exact', kind: 'transparent', expected: f.content.data };
+			}
+		}
+		rules.push(rule);
+	}
+	return rules;
+}
+
+function snapshotCompareOpen() {
+	if (!snapshots.length) {
+		alert(t('No snapshots defined.'));
+		return;
+	}
+	let opts = '';
+	for (let i = 0; i < snapshots.length; i++) {
+		opts += '<option value="' + i + '">' + esc(snapshots[i].name) + '</option>';
+	}
+	const master = document.getElementById('snapshot-compare-master');
+	const check = document.getElementById('snapshot-compare-check');
+	master.innerHTML = opts;
+	check.innerHTML = opts;
+	master.value = '0';
+	check.value = String(snapshots.length > 1 ? 1 : 0);
+	let mhtml = '';
+	for (const fid in PROFILER_MASK_PREFIX4_FIDS) {
+		mhtml += '<label class="flex items-center gap-2 text-sm">' +
+			'<input type="checkbox" data-mask-fid="' + fid + '" checked>' +
+			'<span>' + esc(t('Match first 4 bytes for')) + ' ' + esc(PROFILER_MASK_PREFIX4_FIDS[fid]) + '</span></label>';
+	}
+	document.getElementById('snapshot-compare-mask').innerHTML = mhtml;
+	document.getElementById('snapshot-compare-modal').classList.remove('hidden');
+}
+
+function profilerExtraFileResults(master, check) {
+	const masterPaths = new Set((master.files || []).map(f => (f.path || '').toUpperCase()));
+	return (check.files || []).filter(f => !masterPaths.has((f.path || '').toUpperCase())).map(f => ({
+		path: f.path,
+		name: f.name,
+		status: 'fail',
+		checks: [{ label: 'extra file', expected: 'absent', actual: 'present', ok: false }],
+	}));
+}
+
+async function snapshotCompareRun() {
+	const master = snapshots[+document.getElementById('snapshot-compare-master').value];
+	const check = snapshots[+document.getElementById('snapshot-compare-check').value];
+	if (!master || !check) return;
+	const maskFids = new Set();
+	document.querySelectorAll('#snapshot-compare-mask input[data-mask-fid]').forEach(cb => {
+		if (cb.checked) maskFids.add(cb.getAttribute('data-mask-fid'));
+	});
+	document.getElementById('snapshot-compare-modal').classList.add('hidden');
+	const pseudo = { name: master.name + ' → ' + check.name, rules: profilerRulesFromSnapshot(master, maskFids) };
+	await profilerRunProfile(pseudo, profilerSnapshotSource(check), pseudo.name, profilerExtraFileResults(master, check));
+}
+
 function profilerToggleMismatchOnly(checked) {
 	profilerMismatchOnly = checked;
 	profilerRenderResultsView();
@@ -8458,7 +8562,9 @@ function profilerRenderReport(results) {
 		if (r.error) html += '<div class="text-xs text-yellow-600 mt-1">' + esc(r.error) + '</div>';
 		for (const c of r.checks) {
 			if (c.ok) continue;
-			if (profilerRawDataCheck(c)) {
+			if (c.label === 'extra file') {
+				html += '<div class="text-xs text-red-600 mt-1">' + esc(t('extra file')) + '</div>';
+			} else if (profilerRawDataCheck(c)) {
 				html += '<div class="mt-1">';
 				html += '<div class="text-xs text-red-600 font-mono pl-2">' + esc(c.label) + '</div>';
 				html += '<div class="flex items-center gap-2 mt-0.5 pl-2">' +
@@ -8687,6 +8793,11 @@ const LANG_RU = {
 	'Import profile': 'Импорт профиля',
 	'Profiles': 'Профили',
 	'Card snapshots': 'Снимки карт',
+	'Compare snapshots': 'Сравнить снимки',
+	'Master snapshot': 'Эталонный снимок',
+	'Snapshot to check': 'Снимок для проверки',
+	'Compare': 'Сравнить',
+	'extra file': 'лишний файл',
 	'Check card snapshot': 'Проверить снимок карты',
 	'Select card snapshot': 'Выберите снимок карты',
 	'Content not captured in snapshot': 'Содержимое не захвачено в снимок',
diff --git a/frontend/sw.js b/frontend/sw.js
index 1103bb3..feed8e0 100644
--- a/frontend/sw.js
+++ b/frontend/sw.js
@@ -1,4 +1,4 @@
-const CACHE = 'otaman-v87';
+const CACHE = 'otaman-v88';
 const URLS = [
   'index.html',
   'help.html',
diff --git a/frontend/tests/profiler.test.js b/frontend/tests/profiler.test.js
index 01317da..cde6bbc 100644
--- a/frontend/tests/profiler.test.js
+++ b/frontend/tests/profiler.test.js
@@ -21,7 +21,7 @@ function extractFunc(src, name, asyncFn) {
 	return (asyncFn ? 'async ' : '') + src.slice(m.index, i + 1);
 }
 
-const FNS = ['profilerNormHex', 'profilerNormHexStrict', 'profilerMatch', 'profilerMatchMin', 'profilerMaskPrefix4', 'profilerFileFields', 'profilerContentKindForFileType', 'profilerEmptyRecordContent', 'profilerValidateProfile', 'profilerCustomNameForPath', 'profilerUpdateRulePath', 'profilerResultAspects', 'profilerAspectSummary', 'profilerNumRanges', 'esc', 'escHtml', 'profilerRawDataCheck', 'profilerRenderReport', 'parseBerLen', 'parseTlvList', 'fcpInt', 'fcpParseTlvs', 'fcpFileDescriptor', 'fcpLifeCycle', 'fcpSfi', 'fcpDo', 'fcpDecode', 'fcpDiffHtml', 'profilerFciPreviewItems', 'profilerUpdateFciPreview', 'profilerUpdateRule', 'profilerFciInput', 'profilerScanToggleAll', 'profilerScanIgnoreAllState', 'swapNibbles', 'decIccid', 'profilerSnapshotIccid', 'profilerValidateSnapshot', 'profilerListSwitch', 'profilerScanRefreshOptions', 'profilerLiveSource', 'profilerSnapshotSource', 'profilerVisibleResults'];
+const FNS = ['profilerNormHex', 'profilerNormHexStrict', 'profilerMatch', 'profilerMatchMin', 'profilerMaskPrefix4', 'profilerFileFields', 'profilerContentKindForFileType', 'profilerEmptyRecordContent', 'profilerValidateProfile', 'profilerCustomNameForPath', 'profilerUpdateRulePath', 'profilerResultAspects', 'profilerAspectSummary', 'profilerNumRanges', 'esc', 'escHtml', 'profilerRawDataCheck', 'profilerRenderReport', 'parseBerLen', 'parseTlvList', 'fcpInt', 'fcpParseTlvs', 'fcpFileDescriptor', 'fcpLifeCycle', 'fcpSfi', 'fcpDo', 'fcpDecode', 'fcpDiffHtml', 'profilerFciPreviewItems', 'profilerUpdateFciPreview', 'profilerUpdateRule', 'profilerFciInput', 'profilerScanToggleAll', 'profilerScanIgnoreAllState', 'swapNibbles', 'decIccid', 'profilerSnapshotIccid', 'profilerValidateSnapshot', 'profilerListSwitch', 'profilerScanRefreshOptions', 'profilerLiveSource', 'profilerSnapshotSource', 'profilerVisibleResults', 'profilerMaskFidForFile', 'profilerRulesFromSnapshot', 'profilerExtraFileResults'];
 let code = '';
 for (const f of FNS) code += extractFunc(html, f) + '\n';
 code += extractFunc(html, 'profilerBuildFileRule', true) + '\n';
@@ -1036,3 +1036,79 @@ test('profilerVisibleResults hides passing files when mismatch-only is on', () =
 	assert.deepStrictEqual(profilerVisibleResults(results, true).map(r => r.status), ['fail', 'error']);
 	assert.strictEqual(profilerVisibleResults([{ status: 'pass' }], true).length, 0);
 });
+
+// --- snapshot comparison ---
+
+function masterSnap(files) {
+	return { files: files };
+}
+
+test('profilerRulesFromSnapshot builds exact-FCI rules from the master snapshot', () => {
+	const master = masterSnap([
+		snapFile('MF/7F20/6F07', { name: 'EF.IMSI', fileSize: 9, content: { kind: 'transparent', data: '082905911234567890' } }),
+		snapFile('MF/6F3A', { fileType: 'linear_fixed', fileSize: null, recordLen: 2, numRecords: 1, content: { kind: 'record', records: [{ num: 1, data: 'AABB' }] } }),
+		snapFile('MF/6F3B', { content: null }),
+	]);
+	const rules = profilerRulesFromSnapshot(master, null);
+	assert.strictEqual(rules.length, 3);
+	assert.strictEqual(rules[0].fciMode, 'exact');
+	assert.strictEqual(rules[0].fciHex, '621082024021');
+	assert.deepStrictEqual(rules[0].content, { mode: 'exact', kind: 'transparent', expected: '082905911234567890' });
+	assert.deepStrictEqual(rules[1].content, { mode: 'exact', kind: 'record', records: [{ num: 1, data: 'AABB' }] });
+	assert.strictEqual(rules[2].content, null);
+});
+
+test('profilerRulesFromSnapshot masks only the checked FIDs', () => {
+	const master = masterSnap([
+		snapFile('MF/7F20/6F07', { name: 'EF.IMSI', content: { kind: 'transparent', data: '082905911234567890' } }),
+		snapFile('MF/2FE2', { name: 'EF.ICCID', content: { kind: 'transparent', data: '98680012345678901234' } }),
+		snapFile('MF/6F3A', { content: { kind: 'transparent', data: 'AABBCCDD' } }),
+	]);
+	const rules = profilerRulesFromSnapshot(master, new Set(['6F07']));
+	assert.deepStrictEqual(rules[0].content, { mode: 'mask', kind: 'transparent', expected: '08290591??????????' });
+	assert.deepStrictEqual(rules[1].content, { mode: 'exact', kind: 'transparent', expected: '98680012345678901234' });
+	assert.deepStrictEqual(rules[2].content, { mode: 'exact', kind: 'transparent', expected: 'AABBCCDD' });
+});
+
+test('profilerRulesFromSnapshot falls back to the symbolic name for masking', () => {
+	const master = masterSnap([snapFile('MF/CUSTOM1', { name: 'EF.ICCID', content: { kind: 'transparent', data: '98680012345678901234' } })]);
+	const rules = profilerRulesFromSnapshot(master, new Set(['2FE2']));
+	assert.strictEqual(rules[0].content.mode, 'mask');
+});
+
+test('snapshot comparison passes on an identical snapshot', async () => {
+	const files = [snapFile('MF/7F20/6F07', { name: 'EF.IMSI', fileSize: 9, content: { kind: 'transparent', data: '082905911234567890' } })];
+	const rules = profilerRulesFromSnapshot(masterSnap(files), new Set(['6F07']));
+	const source = profilerSnapshotSource(masterSnap(files.map(f => ({ ...f }))));
+	for (const r of rules) {
+		assert.strictEqual((await profilerRunRule(r, source)).status, 'pass');
+	}
+});
+
+test('snapshot comparison fails on a contents difference', async () => {
+	const master = masterSnap([snapFile('MF/6F3A')]);
+	const check = masterSnap([snapFile('MF/6F3A', { content: { kind: 'transparent', data: 'CCDD' } })]);
+	const rules = profilerRulesFromSnapshot(master, null);
+	const res = await profilerRunRule(rules[0], profilerSnapshotSource(check));
+	assert.strictEqual(res.status, 'fail');
+	assert.ok(res.checks.some(c => c.label === 'content' && c.ok === false));
+});
+
+test('snapshot comparison mask ignores only the first 4 bytes', async () => {
+	const master = masterSnap([snapFile('MF/7F20/6F07', { name: 'EF.IMSI', fileSize: 8, content: { kind: 'transparent', data: '0829059112345678' } })]);
+	const rules = profilerRulesFromSnapshot(master, new Set(['6F07']));
+	const same = masterSnap([snapFile('MF/7F20/6F07', { name: 'EF.IMSI', fileSize: 8, content: { kind: 'transparent', data: '0829059199999999' } })]);
+	const other = masterSnap([snapFile('MF/7F20/6F07', { name: 'EF.IMSI', fileSize: 8, content: { kind: 'transparent', data: '0829059912345678' } })]);
+	assert.strictEqual((await profilerRunRule(rules[0], profilerSnapshotSource(same))).status, 'pass');
+	assert.strictEqual((await profilerRunRule(rules[0], profilerSnapshotSource(other))).status, 'fail');
+});
+
+test('profilerExtraFileResults reports files missing from the master', () => {
+	const master = masterSnap([snapFile('MF/6F3A')]);
+	const check = masterSnap([snapFile('MF/6f3a'), snapFile('MF/6F3B')]);
+	const extras = profilerExtraFileResults(master, check);
+	assert.strictEqual(extras.length, 1);
+	assert.strictEqual(extras[0].path, 'MF/6F3B');
+	assert.strictEqual(extras[0].status, 'fail');
+	assert.deepStrictEqual(extras[0].checks, [{ label: 'extra file', expected: 'absent', actual: 'present', ok: false }]);
+});