diff --git a/CHANGELOG.md b/CHANGELOG.md
index 328847a..b686214 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 ## [Unreleased] - TBD
 
+### Fixed
+
+- Properly close file descriptors opened by `harfile`.
+
+## [0.3.1] - 2025-08-17
+
 ### Added
 
 - `HarFile.flush` method.
diff --git a/src/harfile/__init__.py b/src/harfile/__init__.py
index 91dbbc5..b89b06b 100644
--- a/src/harfile/__init__.py
+++ b/src/harfile/__init__.py
@@ -53,6 +53,7 @@ class HarFile:
     _comment: str | None
     _is_first_entry: bool = True
     _has_preable: bool = False
+    _is_managed_fd: bool = False
     closed: bool = False
 
     def __init__(
@@ -81,9 +82,13 @@ def open(
         fd: IO[str]
         if isinstance(name_or_fd, (str, PathLike)):
             fd = builtins.open(name_or_fd, "w")
+            is_managed = True
         else:
             fd = name_or_fd
-        return cls(fd=fd, creator=creator, browser=browser, comment=comment)
+            is_managed = False
+        instance = cls(fd=fd, creator=creator, browser=browser, comment=comment)
+        instance._is_managed_fd = is_managed
+        return instance
 
     def close(self) -> None:
         """Close the HAR file."""
@@ -94,6 +99,8 @@ def close(self) -> None:
             self._write_preamble()
             self._has_preable = True
         self._write_postscript()
+        if self._is_managed_fd:
+            self._fd.close()
 
     def flush(self) -> None:
         self._fd.flush()
@@ -109,6 +116,9 @@ def __exit__(
     ) -> None:
         if type is None:
             self.close()
+        elif self._is_managed_fd:
+            self._fd.close()
+        self.closed = True
         return None
 
     def add_entry(
diff --git a/tests/test_har.py b/tests/test_har.py
index 583ad51..274d830 100644
--- a/tests/test_har.py
+++ b/tests/test_har.py
@@ -432,13 +432,15 @@ def test_close():
     buffer = io.StringIO()
     with harfile.open(buffer) as har:
         har.close()
+    assert har.closed
 
 
 def test_exception():
     buffer = io.StringIO()
     with pytest.raises(ZeroDivisionError):
-        with harfile.open(buffer):
+        with harfile.open(buffer) as har:
             raise ZeroDivisionError
+    assert har.closed
     assert buffer.getvalue() == ""
 
 
@@ -451,7 +453,6 @@ def test_with_comments():
         comment="EXAMPLE-3",
     ):
         pass
-    print(buffer.getvalue())
     assert (
         buffer.getvalue()
         == """{