diff --git a/docs/src/install.md b/docs/src/install.md
index 3829c84..a63f53e 100644
--- a/docs/src/install.md
+++ b/docs/src/install.md
@@ -18,13 +18,13 @@ spectrum_utils supports Python version 3.8 and above.
 
 spectrum_utils has the following third-party dependencies:
 
-- [appdirs](https://github.com/ActiveState/appdirs)
 - [fastobo](https://fastobo.readthedocs.io/)
 - [Lark](https://lark-parser.readthedocs.io/)
 - [Matplotlib](https://matplotlib.org/)
 - [Numba](http://numba.pydata.org/)
 - [NumPy](https://www.numpy.org/)
 - [Pandas](https://pandas.pydata.org/)
+- [platformdirs](https://github.com/platformdirs/platformdirs)
 - [Pyteomics](https://pyteomics.readthedocs.io/)
 - [Vega-Altair](https://altair-viz.github.io/)
 
diff --git a/environment.yml b/environment.yml
index 081bf14..98ee250 100644
--- a/environment.yml
+++ b/environment.yml
@@ -5,12 +5,12 @@ channels:
   - conda-forge
 dependencies:
   - altair
-  - appdirs
   - fastobo
   - lark>=1.0
   - matplotlib
   - numba>=0.57
   - numpy
   - pandas
+  - platformdirs
   - pyteomics>=4.5
   - python>=3.8
diff --git a/setup.cfg b/setup.cfg
index b1478ce..6186d4a 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -24,12 +24,12 @@ packages = find:
 include_package_data = True
 python_requires = >=3.8
 install_requires =
-    appdirs
     fastobo
     lark>=1.0
     matplotlib>=3.5
     numba>=0.57
     numpy
+    platformdirs
     pyteomics>=4.5
 
 [options.extras_require]
diff --git a/spectrum_utils/proforma.py b/spectrum_utils/proforma.py
index 5f4f8d2..234424c 100644
--- a/spectrum_utils/proforma.py
+++ b/spectrum_utils/proforma.py
@@ -24,7 +24,7 @@
 )
 from urllib.error import URLError
 
-import appdirs
+import platformdirs
 import fastobo
 import lark
 
@@ -35,7 +35,7 @@
 
 
 # Set to None to disable caching.
-cache_dir = appdirs.user_cache_dir("spectrum_utils", False)
+cache_dir = platformdirs.user_cache_dir("spectrum_utils", False)
 
 
 # noinspection PyArgumentList