diff --git a/hef/catalog.py b/hef/catalog.py
index d4bcc10..56aac04 100644
--- a/hef/catalog.py
+++ b/hef/catalog.py
@@ -5,6 +5,9 @@ from __future__ import annotations
 from dataclasses import dataclass, asdict, fields
 from typing import Optional
 
+import json
+from pathlib import Path
+
 MODES = frozenset({"audio", "video", "av"})
 LICENSES = frozenset({"public_domain", "cc0", "cc_by", "cc_by_nc"})
 REVIEW_STATUSES = frozenset({"proposed", "approved"})
@@ -87,3 +90,39 @@ def record_from_dict(data: dict) -> Record:
         return Record(**data)
     except TypeError as exc:
         raise CatalogError(str(exc)) from exc
+
+
+def load_catalog(path) -> list[Record]:
+    """Load and validate every record from a JSONL file. Blank lines skipped."""
+    path = Path(path)
+    records: list[Record] = []
+    with path.open("r", encoding="utf-8") as fh:
+        for lineno, raw in enumerate(fh, start=1):
+            line = raw.strip()
+            if not line:
+                continue
+            try:
+                data = json.loads(line)
+            except json.JSONDecodeError as exc:
+                raise CatalogError(f"line {lineno}: invalid JSON: {exc}") from exc
+            record = record_from_dict(data)
+            validate(record)
+            records.append(record)
+    return records
+
+
+def save_catalog(records, path) -> None:
+    """Validate and write all records to a JSONL file (overwrites)."""
+    path = Path(path)
+    with path.open("w", encoding="utf-8") as fh:
+        for record in records:
+            validate(record)
+            fh.write(json.dumps(record_to_dict(record), ensure_ascii=False) + "\n")
+
+
+def append_record(record, path) -> None:
+    """Validate and append a single record to a JSONL file."""
+    validate(record)
+    path = Path(path)
+    with path.open("a", encoding="utf-8") as fh:
+        fh.write(json.dumps(record_to_dict(record), ensure_ascii=False) + "\n")
diff --git a/tests/test_catalog.py b/tests/test_catalog.py
index 6ed5f13..b23b721 100644
--- a/tests/test_catalog.py
+++ b/tests/test_catalog.py
@@ -92,3 +92,62 @@ def test_record_from_dict_rejects_missing_required_field():
     del data["title"]
     with pytest.raises(CatalogError):
         record_from_dict(data)
+
+
+from hef.catalog import load_catalog, save_catalog, append_record
+
+
+def test_save_then_load_round_trip(tmp_path):
+    path = tmp_path / "library.jsonl"
+    records = [make_record(id="a"), make_record(id="b", mode="audio")]
+    save_catalog(records, path)
+    loaded = load_catalog(path)
+    assert loaded == records
+
+
+def test_load_skips_blank_lines(tmp_path):
+    path = tmp_path / "library.jsonl"
+    save_catalog([make_record(id="a")], path)
+    with path.open("a", encoding="utf-8") as fh:
+        fh.write("\n   \n")
+    loaded = load_catalog(path)
+    assert len(loaded) == 1
+
+
+def test_load_empty_file_returns_empty_list(tmp_path):
+    path = tmp_path / "library.jsonl"
+    path.write_text("", encoding="utf-8")
+    assert load_catalog(path) == []
+
+
+def test_load_invalid_json_raises(tmp_path):
+    path = tmp_path / "library.jsonl"
+    path.write_text("{not json}\n", encoding="utf-8")
+    with pytest.raises(CatalogError):
+        load_catalog(path)
+
+
+def test_load_validates_records(tmp_path):
+    path = tmp_path / "library.jsonl"
+    save_catalog([make_record(id="a")], path)
+    import json
+    bad = record_to_dict(make_record(id="bad"))
+    bad["left"] = 9
+    with path.open("a", encoding="utf-8") as fh:
+        fh.write(json.dumps(bad) + "\n")
+    with pytest.raises(CatalogError):
+        load_catalog(path)
+
+
+def test_append_record(tmp_path):
+    path = tmp_path / "library.jsonl"
+    save_catalog([make_record(id="a")], path)
+    append_record(make_record(id="b"), path)
+    loaded = load_catalog(path)
+    assert [r.id for r in loaded] == ["a", "b"]
+
+
+def test_save_rejects_invalid_record(tmp_path):
+    path = tmp_path / "library.jsonl"
+    with pytest.raises(CatalogError):
+        save_catalog([make_record(mode="hologram")], path)