diff --git a/anytree/config.py b/anytree/config.py
new file mode 100644
index 0000000..55a163c
--- /dev/null
+++ b/anytree/config.py
@@ -0,0 +1,6 @@
+"""Central Configuration."""
+
+import os
+
+# Global Option which enables all internal assertions.
+ASSERTIONS = bool(int(os.environ.get("ANYTREE_ASSERTIONS", 0)))
diff --git a/anytree/importer/dictimporter.py b/anytree/importer/dictimporter.py
index 35e927d..e0adb8d 100644
--- a/anytree/importer/dictimporter.py
+++ b/anytree/importer/dictimporter.py
@@ -1,6 +1,8 @@
 # -*- coding: utf-8 -*-
 from anytree import AnyNode
 
+from ..config import ASSERTIONS
+
 
 class DictImporter:
     """
@@ -38,8 +40,9 @@ def import_(self, data):
         return self.__import(data)
 
     def __import(self, data, parent=None):
-        assert isinstance(data, dict)
-        assert "parent" not in data
+        if ASSERTIONS:  # pragma: no branch
+            assert isinstance(data, dict)
+            assert "parent" not in data
         attrs = dict(data)
         children = attrs.pop("children", [])
         node = self.nodecls(parent=parent, **attrs)
diff --git a/anytree/iterators/zigzaggroupiter.py b/anytree/iterators/zigzaggroupiter.py
index a9ce59b..1f53254 100644
--- a/anytree/iterators/zigzaggroupiter.py
+++ b/anytree/iterators/zigzaggroupiter.py
@@ -1,3 +1,4 @@
+from ..config import ASSERTIONS
 from .abstractiter import AbstractIter
 from .levelordergroupiter import LevelOrderGroupIter
 
@@ -46,7 +47,8 @@ class ZigZagGroupIter(AbstractIter):
     @staticmethod
     def _iter(children, filter_, stop, maxlevel):
         if children:
-            assert len(children) == 1
+            if ASSERTIONS:  # pragma: no branch
+                assert len(children) == 1
             _iter = LevelOrderGroupIter(children[0], filter_, stop, maxlevel)
             while True:
                 try:
diff --git a/anytree/node/nodemixin.py b/anytree/node/nodemixin.py
index 37002b1..9224417 100644
--- a/anytree/node/nodemixin.py
+++ b/anytree/node/nodemixin.py
@@ -4,6 +4,7 @@
 
 from anytree.iterators import PreOrderIter
 
+from ..config import ASSERTIONS
 from .exceptions import LoopError, TreeError
 
 
@@ -146,7 +147,8 @@ def __detach(self, parent):
         if parent is not None:
             self._pre_detach(parent)
             parentchildren = parent.__children_or_empty
-            assert any(child is self for child in parentchildren), "Tree is corrupt."  # pragma: no cover
+            if ASSERTIONS:  # pragma: no branch
+                assert any(child is self for child in parentchildren), "Tree is corrupt."  # pragma: no cover
             # ATOMIC START
             parent.__children = [child for child in parentchildren if child is not self]
             self.__parent = None
@@ -158,7 +160,8 @@ def __attach(self, parent):
         if parent is not None:
             self._pre_attach(parent)
             parentchildren = parent.__children_or_empty
-            assert not any(child is self for child in parentchildren), "Tree is corrupt."  # pragma: no cover
+            if ASSERTIONS:  # pragma: no branch
+                assert not any(child is self for child in parentchildren), "Tree is corrupt."  # pragma: no cover
             # ATOMIC START
             parentchildren.append(self)
             self.__parent = parent
@@ -249,7 +252,8 @@ def children(self, children):
             for child in children:
                 child.parent = self
             self._post_attach_children(children)
-            assert len(self.children) == len(children)
+            if ASSERTIONS:  # pragma: no branch
+                assert len(self.children) == len(children)
         except Exception:
             self.children = old_children
             raise
@@ -261,7 +265,8 @@ def children(self):
         self._pre_detach_children(children)
         for child in self.children:
             child.parent = None
-        assert len(self.children) == 0
+        if ASSERTIONS:  # pragma: no branch
+            assert len(self.children) == 0
         self._post_detach_children(children)
 
     def _pre_detach_children(self, children):
diff --git a/anytree/render.py b/anytree/render.py
index c777df9..155330e 100644
--- a/anytree/render.py
+++ b/anytree/render.py
@@ -13,6 +13,8 @@
 
 import six
 
+from .config import ASSERTIONS
+
 Row = collections.namedtuple("Row", ("pre", "fill", "node"))
 
 
@@ -34,11 +36,12 @@ def __init__(self, vertical, cont, end):
         self.vertical = vertical
         self.cont = cont
         self.end = end
-        assert len(cont) == len(vertical) == len(end), "'%s', '%s' and '%s' need to have equal length" % (
-            vertical,
-            cont,
-            end,
-        )
+        if ASSERTIONS:  # pragma: no branch
+            assert len(cont) == len(vertical) == len(end), "'%s', '%s' and '%s' need to have equal length" % (
+                vertical,
+                cont,
+                end,
+            )
 
     @property
     def empty(self):
diff --git a/anytree/resolver.py b/anytree/resolver.py
index a6b222b..0fe8fea 100644
--- a/anytree/resolver.py
+++ b/anytree/resolver.py
@@ -5,6 +5,8 @@
 
 import re
 
+from .config import ASSERTIONS
+
 _MAXCACHE = 20
 
 
@@ -203,7 +205,8 @@ def __start(self, node, path, cmp_):
         return node, parts
 
     def __glob(self, node, parts):
-        assert node is not None
+        if ASSERTIONS:  # pragma: no branch
+            assert node is not None
         nodes = []
         if parts:
             name = parts[0]
diff --git a/anytree/walker.py b/anytree/walker.py
index da7d91f..88f7daa 100644
--- a/anytree/walker.py
+++ b/anytree/walker.py
@@ -1,5 +1,7 @@
 # -*- coding: utf-8 -*-
 
+from .config import ASSERTIONS
+
 
 class Walker:
     """Walk from one node to another."""
@@ -70,7 +72,8 @@ def walk(start, end):
             raise WalkError(msg)
         # common
         common = Walker.__calc_common(startpath, endpath)
-        assert common[0] is start.root
+        if ASSERTIONS:  # pragma: no branch
+            assert common[0] is start.root
         len_common = len(common)
         # upwards
         if start is common[-1]:
diff --git a/docs/api/anytree.node.rst b/docs/api/anytree.node.rst
index 26ddbb0..ad3f93f 100644
--- a/docs/api/anytree.node.rst
+++ b/docs/api/anytree.node.rst
@@ -8,6 +8,7 @@ Node Classes
 .. automodule:: anytree.node.node
 
 .. automodule:: anytree.node.nodemixin
+    :private-members:
 
 .. automodule:: anytree.node.symlinknode
 
diff --git a/docs/intro.rst b/docs/intro.rst
index 4ff405a..d5c42d3 100644
--- a/docs/intro.rst
+++ b/docs/intro.rst
@@ -115,8 +115,8 @@ Detach/Attach Protocol
 ----------------------
 
 A node class implementation might implement the notification slots
-:any:`_pre_detach(parent)`, :any:`_post_detach(parent)`,
-:any:`_pre_attach(parent)`, :any:`_post_attach(parent)`.
+``_pre_detach(parent)``, ``_post_detach(parent)``,
+``_pre_attach(parent)``, ``_post_attach(parent)``.
 
 These methods are *protected* methods,
 intended to be overwritten by child classes of :any:`NodeMixin`/:any:`Node`.
@@ -163,9 +163,9 @@ _post_detach NotifiedNode('/b')
 
 
 .. important::
-    An exception raised by :any:`_pre_detach(parent)` and :any:`_pre_attach(parent)` will **prevent** the tree structure to be updated.
+    An exception raised by ``_pre_detach(parent)`` and ``_pre_attach(parent)`` will **prevent** the tree structure to be updated.
     The node keeps the old state.
-    An exception raised by :any:`_post_detach(parent)` and :any:`_post_attach(parent)` does **not rollback** the tree structure modification.
+    An exception raised by ``_post_detach(parent)`` and ``_post_attach(parent)`` does **not rollback** the tree structure modification.
 
 
 Custom Separator
diff --git a/docs/tricks.rst b/docs/tricks.rst
index 748864a..40562df 100644
--- a/docs/tricks.rst
+++ b/docs/tricks.rst
@@ -8,3 +8,4 @@ Tricks
     tricks/yaml
     tricks/multidim
     tricks/weightededges
+    tricks/consistencychecks
diff --git a/docs/tricks/consistencychecks.rst b/docs/tricks/consistencychecks.rst
new file mode 100644
index 0000000..692650f
--- /dev/null
+++ b/docs/tricks/consistencychecks.rst
@@ -0,0 +1,13 @@
+Consistency Checks vs. Speed
+============================
+
+Anytree can run some *costly* internal consistency checks.
+With version 2.9.2 these got disabled by default.
+In case of any concerns about the internal data consistency or just for safety, either
+
+* set the environment variable ``ANYTREE_ASSERTIONS=1``, or
+* add the following lines to your code:
+
+>>> import anytree
+>>> anytree.config.ASSERTIONS = True
+
diff --git a/pyproject.toml b/pyproject.toml
index 6f20245..05af691 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -74,7 +74,7 @@ line_length = 120
 exclude_lines = [
     'return NotImplemented',
     'raise NotImplementedError()',
-    'pragma: no cover'
+    'pragma: no cover',
 ]
 
 
@@ -102,6 +102,9 @@ basepython = python3
 
 [testenv]
 allowlist_externals = *
+setenv =
+    ANYTREE_ASSERTIONS=1
+
 commands =
     poetry install --with=test --with=doc
     poetry run black .