diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 0ac84374e..e1482ea4e 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,4 +1,4 @@
-exclude: "asdf/(extern||_jsonschema)/.*"
+exclude: "asdf/(_extern||_jsonschema)/.*"
 repos:
 
 - repo: https://github.com/pre-commit/pre-commit-hooks
diff --git a/asdf/_block/io.py b/asdf/_block/io.py
index ce93f9a11..bfb1c3338 100644
--- a/asdf/_block/io.py
+++ b/asdf/_block/io.py
@@ -10,7 +10,7 @@
 
 import yaml
 
-from asdf import compression as mcompression
+from asdf import _compression as mcompression
 from asdf import constants, util
 
 from .exceptions import BlockIndexError
diff --git a/asdf/_block/options.py b/asdf/_block/options.py
index 1ced09478..04cde9dff 100644
--- a/asdf/_block/options.py
+++ b/asdf/_block/options.py
@@ -1,4 +1,4 @@
-from asdf import compression as mcompression
+from asdf import _compression as mcompression
 from asdf.config import get_config
 
 
diff --git a/asdf/compression.py b/asdf/_compression.py
similarity index 100%
rename from asdf/compression.py
rename to asdf/_compression.py
diff --git a/asdf/core/__init__.py b/asdf/_core/__init__.py
similarity index 100%
rename from asdf/core/__init__.py
rename to asdf/_core/__init__.py
diff --git a/asdf/core/_converters/__init__.py b/asdf/_core/_converters/__init__.py
similarity index 100%
rename from asdf/core/_converters/__init__.py
rename to asdf/_core/_converters/__init__.py
diff --git a/asdf/core/_converters/complex.py b/asdf/_core/_converters/complex.py
similarity index 100%
rename from asdf/core/_converters/complex.py
rename to asdf/_core/_converters/complex.py
diff --git a/asdf/core/_converters/constant.py b/asdf/_core/_converters/constant.py
similarity index 100%
rename from asdf/core/_converters/constant.py
rename to asdf/_core/_converters/constant.py
diff --git a/asdf/core/_converters/external_reference.py b/asdf/_core/_converters/external_reference.py
similarity index 100%
rename from asdf/core/_converters/external_reference.py
rename to asdf/_core/_converters/external_reference.py
diff --git a/asdf/core/_converters/integer.py b/asdf/_core/_converters/integer.py
similarity index 100%
rename from asdf/core/_converters/integer.py
rename to asdf/_core/_converters/integer.py
diff --git a/asdf/core/_converters/ndarray.py b/asdf/_core/_converters/ndarray.py
similarity index 100%
rename from asdf/core/_converters/ndarray.py
rename to asdf/_core/_converters/ndarray.py
diff --git a/asdf/core/_converters/reference.py b/asdf/_core/_converters/reference.py
similarity index 100%
rename from asdf/core/_converters/reference.py
rename to asdf/_core/_converters/reference.py
diff --git a/asdf/core/_converters/tree.py b/asdf/_core/_converters/tree.py
similarity index 100%
rename from asdf/core/_converters/tree.py
rename to asdf/_core/_converters/tree.py
diff --git a/asdf/core/_extensions.py b/asdf/_core/_extensions.py
similarity index 100%
rename from asdf/core/_extensions.py
rename to asdf/_core/_extensions.py
diff --git a/asdf/core/_integration.py b/asdf/_core/_integration.py
similarity index 100%
rename from asdf/core/_integration.py
rename to asdf/_core/_integration.py
diff --git a/asdf/core/_validators/__init__.py b/asdf/_core/_validators/__init__.py
similarity index 100%
rename from asdf/core/_validators/__init__.py
rename to asdf/_core/_validators/__init__.py
diff --git a/asdf/core/_validators/ndarray.py b/asdf/_core/_validators/ndarray.py
similarity index 100%
rename from asdf/core/_validators/ndarray.py
rename to asdf/_core/_validators/ndarray.py
diff --git a/asdf/entry_points.py b/asdf/_entry_points.py
similarity index 100%
rename from asdf/entry_points.py
rename to asdf/_entry_points.py
diff --git a/asdf/extern/RangeHTTPServer.py b/asdf/_extern/RangeHTTPServer.py
similarity index 100%
rename from asdf/extern/RangeHTTPServer.py
rename to asdf/_extern/RangeHTTPServer.py
diff --git a/asdf/extern/__init__.py b/asdf/_extern/__init__.py
similarity index 100%
rename from asdf/extern/__init__.py
rename to asdf/_extern/__init__.py
diff --git a/asdf/extern/atomicfile.py b/asdf/_extern/atomicfile.py
similarity index 100%
rename from asdf/extern/atomicfile.py
rename to asdf/_extern/atomicfile.py
diff --git a/asdf/_tests/core/tests/test_integration.py b/asdf/_tests/core/tests/test_integration.py
index b808dc729..1ef979978 100644
--- a/asdf/_tests/core/tests/test_integration.py
+++ b/asdf/_tests/core/tests/test_integration.py
@@ -2,7 +2,7 @@
 import yaml
 
 import asdf
-from asdf.core._integration import get_extensions, get_json_schema_resource_mappings
+from asdf._core._integration import get_extensions, get_json_schema_resource_mappings
 
 
 @pytest.mark.parametrize(
diff --git a/asdf/_tests/httpserver.py b/asdf/_tests/httpserver.py
index 8e9d3956f..3de3f62d2 100644
--- a/asdf/_tests/httpserver.py
+++ b/asdf/_tests/httpserver.py
@@ -6,7 +6,7 @@
 import tempfile
 import threading
 
-from asdf.extern.RangeHTTPServer import RangeHTTPRequestHandler
+from asdf._extern.RangeHTTPServer import RangeHTTPRequestHandler
 
 __all__ = ["HTTPServer", "RangeHTTPServer"]
 
diff --git a/asdf/_tests/test_asdf.py b/asdf/_tests/test_asdf.py
index 8584367d8..e5f56bf99 100644
--- a/asdf/_tests/test_asdf.py
+++ b/asdf/_tests/test_asdf.py
@@ -3,9 +3,9 @@
 import pytest
 
 from asdf import config_context
+from asdf._entry_points import get_extensions
 from asdf._tests._helpers import assert_no_warnings, assert_tree_match, yaml_to_asdf
 from asdf.asdf import AsdfFile, open_asdf
-from asdf.entry_points import get_extensions
 from asdf.exceptions import AsdfWarning
 from asdf.extension import ExtensionProxy
 from asdf.versioning import AsdfVersion
diff --git a/asdf/_tests/test_compression.py b/asdf/_tests/test_compression.py
index 150d27cc5..091d405cf 100644
--- a/asdf/_tests/test_compression.py
+++ b/asdf/_tests/test_compression.py
@@ -6,7 +6,7 @@
 import pytest
 
 import asdf
-from asdf import compression, config_context, generic_io
+from asdf import _compression, config_context, generic_io
 from asdf._tests import _helpers as helpers
 from asdf.extension import Compressor, Extension
 
@@ -71,27 +71,27 @@ def test_invalid_compression():
     with pytest.raises(ValueError, match=r"Invalid compression type: foo"):
         ff.set_array_compression(tree["science_data"], "foo")
     with pytest.raises(ValueError, match=r"Unknown compression type: .*"):
-        compression._get_compressor("foo")
+        _compression._get_compressor("foo")
 
 
 def test_get_compressed_size():
-    assert compression.get_compressed_size(b"0" * 1024, "zlib") < 1024
+    assert _compression.get_compressed_size(b"0" * 1024, "zlib") < 1024
 
 
 def test_decompress_too_long_short():
     fio = io.BytesIO()
-    compression.compress(fio, b"0" * 1024, "zlib")
+    _compression.compress(fio, b"0" * 1024, "zlib")
     size = fio.tell()
     fio.seek(0)
     blocks = lambda us: [fio.read(us)]  # noqa: E731
     fio.read_blocks = blocks
-    compression.decompress(fio, size, 1024, "zlib")
+    _compression.decompress(fio, size, 1024, "zlib")
     fio.seek(0)
     with pytest.raises(ValueError, match=r"Decompressed data wrong size"):
-        compression.decompress(fio, size, 1025, "zlib")
+        _compression.decompress(fio, size, 1025, "zlib")
     fio.seek(0)
     with pytest.raises(ValueError, match=r"memoryview assignment: lvalue and rvalue have different structures"):
-        compression.decompress(fio, size, 1023, "zlib")
+        _compression.decompress(fio, size, 1023, "zlib")
 
 
 def test_zlib(tmp_path):
diff --git a/asdf/_tests/test_config.py b/asdf/_tests/test_config.py
index 0b90ec14a..0e082deb3 100644
--- a/asdf/_tests/test_config.py
+++ b/asdf/_tests/test_config.py
@@ -5,7 +5,7 @@
 
 import asdf
 from asdf import get_config
-from asdf.core._integration import get_json_schema_resource_mappings
+from asdf._core._integration import get_json_schema_resource_mappings
 from asdf.extension import ExtensionProxy
 from asdf.resource import ResourceMappingProxy
 
diff --git a/asdf/_tests/test_entry_points.py b/asdf/_tests/test_entry_points.py
index ec45ca05d..d53c85afc 100644
--- a/asdf/_tests/test_entry_points.py
+++ b/asdf/_tests/test_entry_points.py
@@ -6,7 +6,7 @@
 import importlib_metadata as metadata
 import pytest
 
-from asdf import entry_points
+from asdf import _entry_points
 from asdf._version import version as asdf_package_version
 from asdf.exceptions import AsdfWarning
 from asdf.extension import ExtensionProxy
@@ -20,7 +20,7 @@ def mock_entry_points():
 
 @pytest.fixture(autouse=True)
 def _monkeypatch_entry_points(monkeypatch, mock_entry_points):
-    def _entry_points(*, group):
+    def patched_entry_points(*, group):
         for candidate_group, name, func_name in mock_entry_points:
             if candidate_group == group:
                 point = metadata.EntryPoint(name=name, group=group, value=func_name)
@@ -28,7 +28,7 @@ def _entry_points(*, group):
 
                 yield point
 
-    monkeypatch.setattr(entry_points, "entry_points", _entry_points)
+    monkeypatch.setattr(_entry_points, "entry_points", patched_entry_points)
 
 
 def resource_mappings_entry_point_successful():
@@ -59,7 +59,7 @@ def test_get_resource_mappings(mock_entry_points):
             "asdf._tests.test_entry_points:resource_mappings_entry_point_successful",
         ),
     )
-    mappings = entry_points.get_resource_mappings()
+    mappings = _entry_points.get_resource_mappings()
     assert len(mappings) == 2
     for m in mappings:
         assert isinstance(m, ResourceMappingProxy)
@@ -71,7 +71,7 @@ def test_get_resource_mappings(mock_entry_points):
         ("asdf.resource_mappings", "failing", "asdf._tests.test_entry_points:resource_mappings_entry_point_failing"),
     )
     with pytest.warns(AsdfWarning, match=r"Exception: NOPE"):
-        mappings = entry_points.get_resource_mappings()
+        mappings = _entry_points.get_resource_mappings()
     assert len(mappings) == 0
 
     mock_entry_points.clear()
@@ -83,7 +83,7 @@ def test_get_resource_mappings(mock_entry_points):
         ),
     )
     with pytest.warns(AsdfWarning, match=r"TypeError: Resource mapping must implement the Mapping interface"):
-        mappings = entry_points.get_resource_mappings()
+        mappings = _entry_points.get_resource_mappings()
     assert len(mappings) == 2
 
 
@@ -130,7 +130,7 @@ def test_get_extensions(mock_entry_points):
     mock_entry_points.append(
         ("asdf.extensions", "successful", "asdf._tests.test_entry_points:extensions_entry_point_successful"),
     )
-    extensions = entry_points.get_extensions()
+    extensions = _entry_points.get_extensions()
     assert len(extensions) == 2
     for e in extensions:
         assert isinstance(e, ExtensionProxy)
@@ -142,7 +142,7 @@ def test_get_extensions(mock_entry_points):
         ("asdf.extensions", "failing", "asdf._tests.test_entry_points:extensions_entry_point_failing"),
     )
     with pytest.warns(AsdfWarning, match=r"Exception: NOPE"):
-        extensions = entry_points.get_extensions()
+        extensions = _entry_points.get_extensions()
     assert len(extensions) == 0
 
     mock_entry_points.clear()
@@ -153,16 +153,16 @@ def test_get_extensions(mock_entry_points):
         AsdfWarning,
         match=r"TypeError: Extension must implement the Extension interface",
     ):
-        extensions = entry_points.get_extensions()
+        extensions = _entry_points.get_extensions()
     assert len(extensions) == 2
 
     mock_entry_points.clear()
     mock_entry_points.append(("asdf_extensions", "legacy", "asdf._tests.test_entry_points:LegacyExtension"))
-    extensions = entry_points.get_extensions()
+    extensions = _entry_points.get_extensions()
     assert len(extensions) == 0  # asdf_extensions is no longer supported
 
     mock_entry_points.clear()
     mock_entry_points.append(("asdf.extensions", "failing", "asdf._tests.test_entry_points:FauxLegacyExtension"))
     with pytest.warns(AsdfWarning, match=r"TypeError"):
-        extensions = entry_points.get_extensions()
+        extensions = _entry_points.get_extensions()
     assert len(extensions) == 0
diff --git a/asdf/asdf.py b/asdf/asdf.py
index 924274d8f..fc3ddadbd 100644
--- a/asdf/asdf.py
+++ b/asdf/asdf.py
@@ -8,10 +8,10 @@
 
 from packaging.version import Version
 
+from . import _compression as mcompression
 from . import _display as display
 from . import _node_info as node_info
 from . import _version as version
-from . import compression as mcompression
 from . import constants, generic_io, reference, schema, treeutil, util, versioning, yamlutil
 from ._block.manager import Manager as BlockManager
 from ._helpers import validate_version
diff --git a/asdf/commands/extension.py b/asdf/commands/extension.py
index cc0d0e05e..08eabc665 100644
--- a/asdf/commands/extension.py
+++ b/asdf/commands/extension.py
@@ -1,7 +1,7 @@
 """
 Implementation of command for reporting information about installed extensions.
 """
-from asdf.entry_points import get_extensions
+from asdf._entry_points import get_extensions
 
 from .main import Command
 
diff --git a/asdf/config.py b/asdf/config.py
index 911c7a9b3..8e2dd3ff9 100644
--- a/asdf/config.py
+++ b/asdf/config.py
@@ -7,7 +7,7 @@
 import threading
 from contextlib import contextmanager
 
-from . import entry_points, util, versioning
+from . import _entry_points, util, versioning
 from ._helpers import validate_version
 from .extension import ExtensionProxy
 from .resource import ResourceManager, ResourceMappingProxy
@@ -63,7 +63,7 @@ def resource_mappings(self):
         if self._resource_mappings is None:
             with self._lock:
                 if self._resource_mappings is None:
-                    self._resource_mappings = entry_points.get_resource_mappings()
+                    self._resource_mappings = _entry_points.get_resource_mappings()
         return self._resource_mappings
 
     def add_resource_mapping(self, mapping):
@@ -155,7 +155,7 @@ def extensions(self):
         if self._extensions is None:
             with self._lock:
                 if self._extensions is None:
-                    self._extensions = entry_points.get_extensions()
+                    self._extensions = _entry_points.get_extensions()
         return self._extensions
 
     def add_extension(self, extension):
@@ -371,7 +371,7 @@ def all_array_compression(self):
     @all_array_compression.setter
     def all_array_compression(self, value):
         # local to avoid circular import
-        from asdf.compression import validate
+        from asdf._compression import validate
 
         self._all_array_compression = validate(value)
 
diff --git a/asdf/generic_io.py b/asdf/generic_io.py
index 1ebe660fc..b63563a67 100644
--- a/asdf/generic_io.py
+++ b/asdf/generic_io.py
@@ -20,8 +20,8 @@
 import numpy as np
 
 from . import util
+from ._extern import atomicfile
 from .exceptions import DelimiterNotFoundError
-from .extern import atomicfile
 from .util import _patched_urllib_parse
 
 __all__ = ["get_file", "get_uri", "resolve_uri", "relative_uri"]
diff --git a/pyproject.toml b/pyproject.toml
index 3f954c247..d6aac0724 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -55,8 +55,8 @@ tests = [
 'repository' = 'https://github.com/asdf-format/asdf'
 'tracker' = 'https://github.com/asdf-format/asdf/issues'
 [project.entry-points]
-'asdf.extensions' = {asdf = 'asdf.core._integration:get_extensions'}
-'asdf.resource_mappings' = {asdf = 'asdf.core._integration:get_json_schema_resource_mappings'}
+'asdf.extensions' = {asdf = 'asdf._core._integration:get_extensions'}
+'asdf.resource_mappings' = {asdf = 'asdf._core._integration:get_json_schema_resource_mappings'}
 asdf_extensions = {builtin = 'asdf.extension._legacy:BuiltinExtension'}
 console_scripts = {asdftool = 'asdf.commands.main:main'}
 pytest11 = {asdf_schema_tester = 'pytest_asdf.plugin'}
@@ -90,7 +90,7 @@ force-exclude = '''
     | \.git
     | \.pytest_cache
     | \.tox
-    | asdf/extern
+    | asdf/_extern
     | asdf/_jsonschema
     | build
     | dist
@@ -126,7 +126,7 @@ omit = [
     'asdf/*/*/tests/*',
     'asdf/version.*',
     'asdf/compat*',
-    'asdf/extern*',
+    'asdf/_extern*',
     'asdf/_jsonschema/**',
     # And again for running against installed version
     '*/asdf/_astropy_init*',
@@ -141,7 +141,7 @@ omit = [
     '*/asdf/*/*/tests/*',
     '*/asdf/version.*',
     '*/asdf/compat*',
-    '*/asdf/extern*',
+    '*/asdf/_extern*',
     '*/asdf/_jsonschema/**',
 ]
 
@@ -176,7 +176,7 @@ extend-ignore = [
     "S310", # URL open for permitted schemes
     "RUF012",  # mutable-class-default (typing related)
 ]
-extend-exclude = ["asdf/extern/*", "asdf/_jsonschema/*", "docs/*"]
+extend-exclude = ["asdf/_extern/*", "asdf/_jsonschema/*", "docs/*"]
 
 [tool.ruff.per-file-ignores]
 "test_*.py" = ["S101"]
@@ -184,10 +184,10 @@ extend-exclude = ["asdf/extern/*", "asdf/_jsonschema/*", "docs/*"]
 "compatibility_tests/common.py" = ["S101"]
 
 [tool.flynt]
-exclude = ["asdf/extern/*", "asdf/_jsonschema/*"]
+exclude = ["asdf/_extern/*", "asdf/_jsonschema/*"]
 
 [tool.codespell]
-skip="*.pdf,*.asdf,.tox,asdf/extern,asdf/_jsonschema,build,./tags,.git,docs/_build"
+skip="*.pdf,*.asdf,.tox,asdf/_extern,asdf/_jsonschema,build,./tags,.git,docs/_build"
 ignore-words-list="""
 fo,afile,
 """