diff --git a/appinfo/info.xml b/appinfo/info.xml
index 5a6f1ee..a13b017 100644
--- a/appinfo/info.xml
+++ b/appinfo/info.xml
@@ -5,7 +5,7 @@
     <name>NG Backup</name>
     <summary>Encrypted, incremental backups of your Nextcloud with restore from the web interface</summary>
     <description><![CDATA[Work in progress, not ready for use.]]></description>
-    <version>0.0.2</version>
+    <version>0.0.3</version>
     <licence>agpl</licence>
     <author>Dillard Blom</author>
     <namespace>NgBackup</namespace>
diff --git a/lib/Db/DbIndexCache.php b/lib/Db/DbIndexCache.php
new file mode 100644
index 0000000..bb61dab
--- /dev/null
+++ b/lib/Db/DbIndexCache.php
@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Db;
+
+use OCA\NgBackup\Repository\IIndexCache;
+use OCP\DB\Exception;
+use OCP\IDBConnection;
+
+class DbIndexCache implements IIndexCache {
+	public function __construct(
+		private IDBConnection $db,
+	) {
+	}
+
+	public function all(string $repositoryId): array {
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('pack_id', 'entries')->from('ngb_index')->where($qb->expr()->eq('repository_id', $qb->createNamedParameter($repositoryId)));
+		$result = $qb->executeQuery();
+		$out = [];
+		while ($row = $result->fetch()) {
+			$out[$row['pack_id']] = json_decode($row['entries'], true, 512, JSON_THROW_ON_ERROR);
+		}
+		$result->closeCursor();
+		return $out;
+	}
+
+	public function put(string $repositoryId, string $packId, array $entries): void {
+		$qb = $this->db->getQueryBuilder();
+		$qb->insert('ngb_index')->values([
+			'repository_id' => $qb->createNamedParameter($repositoryId),
+			'pack_id' => $qb->createNamedParameter($packId),
+			'entries' => $qb->createNamedParameter(json_encode($entries, JSON_THROW_ON_ERROR)),
+		]);
+		try {
+			$qb->executeStatement();
+		} catch (Exception $e) {
+			if ($e->getReason() !== Exception::REASON_UNIQUE_CONSTRAINT_VIOLATION) {
+				throw $e;
+			}
+		}
+	}
+
+	public function remove(string $repositoryId, array $packIds): void {
+		foreach (array_chunk($packIds, 500) as $chunk) {
+			$qb = $this->db->getQueryBuilder();
+			$qb->delete('ngb_index')
+				->where($qb->expr()->eq('repository_id', $qb->createNamedParameter($repositoryId)))
+				->andWhere($qb->expr()->in('pack_id', $qb->createNamedParameter($chunk, \OCP\DB\QueryBuilder\IQueryBuilder::PARAM_STR_ARRAY)));
+			$qb->executeStatement();
+		}
+	}
+}
diff --git a/lib/Migration/Version000002Date20261002010000.php b/lib/Migration/Version000002Date20261002010000.php
new file mode 100644
index 0000000..2a6cbab
--- /dev/null
+++ b/lib/Migration/Version000002Date20261002010000.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\DB\Types;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+/** Local cache of the per-pack index files, so opening a repository does not download them all. */
+class Version000002Date20261002010000 extends SimpleMigrationStep {
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+		if (!$schema->hasTable('ngb_index')) {
+			$t = $schema->createTable('ngb_index');
+			$t->addColumn('id', Types::BIGINT, ['autoincrement' => true, 'notnull' => true, 'unsigned' => true]);
+			$t->addColumn('repository_id', Types::STRING, ['notnull' => true, 'length' => 32]);
+			$t->addColumn('pack_id', Types::STRING, ['notnull' => true, 'length' => 32]);
+			// Plain JSON list of blob entries. Blob ids are keyed hashes and reveal no content.
+			$t->addColumn('entries', Types::TEXT, ['notnull' => true]);
+			$t->setPrimaryKey(['id']);
+			$t->addUniqueIndex(['repository_id', 'pack_id'], 'ngb_index_repo_pack');
+		}
+		return $schema;
+	}
+}
diff --git a/lib/Repository/BlobIndex.php b/lib/Repository/BlobIndex.php
index f52a134..a5c3169 100644
--- a/lib/Repository/BlobIndex.php
+++ b/lib/Repository/BlobIndex.php
@@ -24,22 +24,51 @@ final class BlobIndex {
 	/** @var array<string, true> blobs added in this run but whose pack is not uploaded yet */
 	private array $pending = [];
 
+	private ?IIndexCache $cache = null;
+	private string $repositoryId = '';
+	/** @var int index files downloaded by the last load() (for tests and diagnostics) */
+	public int $downloaded = 0;
+
 	public function __construct(
 		private IBackend $backend,
 		private StreamCipher $cipher,
 	) {
 	}
 
+	public function setCache(IIndexCache $cache, string $repositoryId): void {
+		$this->cache = $cache;
+		$this->repositoryId = $repositoryId;
+	}
+
+	/**
+	 * Load the index: one listing of index/, entries from the local cache where available,
+	 * and only the index files that are not cached yet are downloaded. Cached packs that no
+	 * longer exist on the backend are dropped from the cache.
+	 */
 	public function load(): void {
+		$cached = $this->cache?->all($this->repositoryId) ?? [];
+		$present = [];
+		$this->downloaded = 0;
 		foreach ($this->backend->list('index') as $path) {
 			$packId = basename($path);
-			$fh = $this->backend->get($path);
-			$entries = json_decode($this->cipher->decryptString((string)stream_get_contents($fh), 'index:' . $packId), true, 512, JSON_THROW_ON_ERROR);
-			fclose($fh);
+			$present[$packId] = true;
+			if (isset($cached[$packId])) {
+				$entries = $cached[$packId];
+			} else {
+				$fh = $this->backend->get($path);
+				$entries = json_decode($this->cipher->decryptString((string)stream_get_contents($fh), 'index:' . $packId), true, 512, JSON_THROW_ON_ERROR);
+				fclose($fh);
+				$this->downloaded++;
+				$this->cache?->put($this->repositoryId, $packId, $entries);
+			}
 			foreach ($entries as $e) {
 				$this->blobs[$e['id']] = [$packId, $e['offset'], $e['length'], $e['raw'], $e['flags']];
 			}
 		}
+		$stale = array_keys(array_diff_key($cached, $present));
+		if ($stale !== []) {
+			$this->cache?->remove($this->repositoryId, $stale);
+		}
 	}
 
 	public function has(string $id): bool {
@@ -68,6 +97,7 @@ final class BlobIndex {
 		fwrite($stream, $this->cipher->encryptString(json_encode($entries, JSON_THROW_ON_ERROR), 'index:' . $packId));
 		rewind($stream);
 		$this->backend->put('index/' . $packId, $stream);
+		$this->cache?->put($this->repositoryId, $packId, $entries);
 		foreach ($entries as $e) {
 			$this->blobs[$e['id']] = [$packId, $e['offset'], $e['length'], $e['raw'], $e['flags']];
 			unset($this->pending[$e['id']]);
diff --git a/lib/Repository/IIndexCache.php b/lib/Repository/IIndexCache.php
new file mode 100644
index 0000000..1a7cff0
--- /dev/null
+++ b/lib/Repository/IIndexCache.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Repository;
+
+/** Optional local cache of pack index entries (the repository's index/ files stay authoritative). */
+interface IIndexCache {
+	/** @return array<string, list<array{id:string, offset:int, length:int, raw:int, flags:int}>> packId => entries */
+	public function all(string $repositoryId): array;
+
+	/** @param list<array{id:string, offset:int, length:int, raw:int, flags:int}> $entries */
+	public function put(string $repositoryId, string $packId, array $entries): void;
+
+	/** @param list<string> $packIds */
+	public function remove(string $repositoryId, array $packIds): void;
+}
diff --git a/lib/Repository/Repository.php b/lib/Repository/Repository.php
index 7684f7e..4c12d84 100644
--- a/lib/Repository/Repository.php
+++ b/lib/Repository/Repository.php
@@ -64,7 +64,7 @@ final class Repository {
 	}
 
 	/** Open with the master key the server holds (scheduled backups, no passphrase needed). */
-	public static function openWithKey(IBackend $backend, KeyRing $keys): self {
+	public static function openWithKey(IBackend $backend, KeyRing $keys, ?IIndexCache $cache = null): self {
 		$config = self::readConfig($backend);
 		try {
 			$ok = isset($config['check']) && (new StreamCipher($keys))->decryptString((string)base64_decode($config['check'], true), 'config-check') === $config['id'];
@@ -75,10 +75,18 @@ final class Repository {
 			throw new RepositoryException('This repository was created with a different key');
 		}
 		$repo = new self($backend, $keys, $config['id']);
+		if ($cache !== null) {
+			$repo->index->setCache($cache, $config['id']);
+		}
 		$repo->index->load();
 		return $repo;
 	}
 
+	/** Index files downloaded when this repository was opened (0 when the local cache was complete). */
+	public function indexDownloads(): int {
+		return $this->index->downloaded;
+	}
+
 	private static function readConfig(IBackend $backend): array {
 		try {
 			$fh = $backend->get('config');
diff --git a/lib/Service/TargetService.php b/lib/Service/TargetService.php
index 8c0d4d5..ed301ee 100644
--- a/lib/Service/TargetService.php
+++ b/lib/Service/TargetService.php
@@ -28,6 +28,7 @@ class TargetService {
 		private KeyService $keys,
 		private ICrypto $crypto,
 		private IAppManager $appManager,
+		private \OCA\NgBackup\Db\DbIndexCache $indexCache,
 	) {
 	}
 
@@ -98,7 +99,7 @@ class TargetService {
 	}
 
 	public function repository(Target $target): Repository {
-		$repo = Repository::openWithKey($this->backend($target), $this->keys->keyRing());
+		$repo = Repository::openWithKey($this->backend($target), $this->keys->keyRing(), $this->indexCache);
 		if ($target->getRepositoryId() !== null && $repo->id() !== $target->getRepositoryId()) {
 			throw new \RuntimeException('The target now contains a different repository than when it was added');
 		}
diff --git a/tests/.phpunit.result.cache b/tests/.phpunit.result.cache
index e9fa417..b5f6c65 100644
--- a/tests/.phpunit.result.cache
+++ b/tests/.phpunit.result.cache
@@ -1 +1 @@
-{"version":2,"defects":{"OCA\\NgBackup\\Tests\\Unit\\Job\\BackupRunTest::testIncrementalRunInTinyStepsReadsNothing":7},"times":{"OCA\\NgBackup\\Tests\\Unit\\Crypto\\KeyRingTest::testWrapUnwrapKeepsKeys":1.068,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\KeyRingTest::testWrongPassphrase":1.175,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\KeyRingTest::testBlobIdsAreKeyed":0.001,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\KeyRingTest::testRejectsShortMasterKey":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#empty":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#small":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#one frame":0.001,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#frame+1":0.001,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#several":0.003,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testStreamingKeepsMemoryBounded":0.234,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#flipped byte":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#truncated":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#trailing data":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#cut at frame boundary":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#bad magic":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testWrongAssociatedDataIsRejected":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testWrongKeyIsRejected":0,"OCA\\NgBackup\\Tests\\Unit\\Job\\BackupRunTest::testRunInManyTinyStepsRestoresIdentically":1.39,"OCA\\NgBackup\\Tests\\Unit\\Job\\BackupRunTest::testFileChangedBetweenStepsIsReadAgain":1.724,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testBackupAndRestoreAreIdentical":1.985,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testUnchangedRunReadsAndUploadsNothing":1.045,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testChangeInLargeFileUploadsOnlyAffectedBlob":1.175,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testPartialRestore":1.101,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testWrongPassphrase":1.038,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testInitRefusesExistingRepository":1.024,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testTamperedPackIsDetected":1.06,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testBlobWriterAndReadLinesAcrossBlobBoundaries":1.378,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testObjectsAreBoundToTheirPath":0.544,"OCA\\NgBackup\\Tests\\Unit\\Job\\BackupRunTest::testIncrementalRunInTinyStepsReadsNothing":2.984,"OCA\\NgBackup\\Tests\\Unit\\Job\\TreeWalkerTest::testOrderMatchesCompare":0.003,"OCA\\NgBackup\\Tests\\Unit\\Job\\TreeWalkerTest::testResumeAfterCursorYieldsTheRest":0.003,"OCA\\NgBackup\\Tests\\Unit\\Job\\TreeWalkerTest::testExcludeAndMultipleRoots":0.069}}
\ No newline at end of file
+{"version":2,"defects":{"OCA\\NgBackup\\Tests\\Unit\\Job\\BackupRunTest::testIncrementalRunInTinyStepsReadsNothing":7},"times":{"OCA\\NgBackup\\Tests\\Unit\\Crypto\\KeyRingTest::testWrapUnwrapKeepsKeys":1.308,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\KeyRingTest::testWrongPassphrase":1.19,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\KeyRingTest::testBlobIdsAreKeyed":0.002,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\KeyRingTest::testRejectsShortMasterKey":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#empty":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#small":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#one frame":0.001,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#frame+1":0.001,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testRoundTrip#several":0.002,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testStreamingKeepsMemoryBounded":0.24,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#flipped byte":0.001,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#truncated":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#trailing data":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#cut at frame boundary":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testCorruptionIsRejected#bad magic":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testWrongAssociatedDataIsRejected":0,"OCA\\NgBackup\\Tests\\Unit\\Crypto\\StreamCipherTest::testWrongKeyIsRejected":0,"OCA\\NgBackup\\Tests\\Unit\\Job\\BackupRunTest::testRunInManyTinyStepsRestoresIdentically":1.371,"OCA\\NgBackup\\Tests\\Unit\\Job\\BackupRunTest::testFileChangedBetweenStepsIsReadAgain":1.836,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testBackupAndRestoreAreIdentical":1.941,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testUnchangedRunReadsAndUploadsNothing":0.989,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testChangeInLargeFileUploadsOnlyAffectedBlob":1.126,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testPartialRestore":1.068,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testWrongPassphrase":1.097,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testInitRefusesExistingRepository":1.078,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testTamperedPackIsDetected":1.166,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testBlobWriterAndReadLinesAcrossBlobBoundaries":1.189,"OCA\\NgBackup\\Tests\\Unit\\Repository\\RepositoryTest::testObjectsAreBoundToTheirPath":0.529,"OCA\\NgBackup\\Tests\\Unit\\Job\\BackupRunTest::testIncrementalRunInTinyStepsReadsNothing":3.034,"OCA\\NgBackup\\Tests\\Unit\\Job\\TreeWalkerTest::testOrderMatchesCompare":0.003,"OCA\\NgBackup\\Tests\\Unit\\Job\\TreeWalkerTest::testResumeAfterCursorYieldsTheRest":0.004,"OCA\\NgBackup\\Tests\\Unit\\Job\\TreeWalkerTest::testExcludeAndMultipleRoots":0.005,"OCA\\NgBackup\\Tests\\Unit\\Repository\\IndexCacheTest::testSecondOpenDownloadsNoIndexFiles":2.497}}
\ No newline at end of file
diff --git a/tests/Unit/Repository/IndexCacheTest.php b/tests/Unit/Repository/IndexCacheTest.php
new file mode 100644
index 0000000..c2b0c5b
--- /dev/null
+++ b/tests/Unit/Repository/IndexCacheTest.php
@@ -0,0 +1,54 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\NgBackup\Tests\Unit\Repository;
+
+use OCA\NgBackup\Backend\LocalBackend;
+use OCA\NgBackup\Crypto\KeyRing;
+use OCA\NgBackup\Repository\IIndexCache;
+use OCA\NgBackup\Repository\Repository;
+use OCA\NgBackup\Tests\Unit\TempDirTrait;
+use PHPUnit\Framework\TestCase;
+
+class IndexCacheTest extends TestCase {
+	use TempDirTrait;
+
+	public function testSecondOpenDownloadsNoIndexFiles(): void {
+		$cache = new class implements IIndexCache {
+			public array $data = [];
+			public function all(string $r): array { return $this->data[$r] ?? []; }
+			public function put(string $r, string $p, array $e): void { $this->data[$r][$p] = $e; }
+			public function remove(string $r, array $ps): void { foreach ($ps as $p) { unset($this->data[$r][$p]); } }
+		};
+		$src = $this->tempDir();
+		for ($i = 0; $i < 12; $i++) {
+			file_put_contents("$src/f$i", random_bytes(3 * 1048576));
+		}
+		$backend = new LocalBackend($this->tempDir());
+		$keys = KeyRing::generate();
+		Repository::initWithKey($backend, $keys, $keys->wrap('pw'));
+
+		$repo = Repository::openWithKey($backend, $keys, $cache);
+		$r1 = $repo->backupDirectory($src);
+		$this->assertGreaterThan(0, count($backend->list('index')));
+
+		$again = Repository::openWithKey($backend, $keys, $cache);
+		$this->assertSame(0, $again->indexDownloads(), 'everything came from the cache');
+
+		file_put_contents("$src/new", random_bytes(2 * 1048576));
+		$again->backupDirectory($src, $r1['snapshot']);
+		$third = Repository::openWithKey($backend, $keys, $cache);
+		$this->assertSame(0, $third->indexDownloads(), 'packs written by this server are cached on write');
+
+		// A cache that misses entries (e.g. another server wrote packs) fetches only those.
+		$repoId = array_key_first($cache->data);
+		array_pop($cache->data[$repoId]);
+		$fourth = Repository::openWithKey($backend, $keys, $cache);
+		$this->assertSame(1, $fourth->indexDownloads());
+
+		$target = $this->tempDir();
+		$fourth->restore($r1['snapshot'], $target);
+		$this->assertCount(12, self::hashTree($target));
+	}
+}