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/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/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/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 98c45744f..d6aac0724 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -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,
 """