diff --git a/doc/whats-new.rst b/doc/whats-new.rst
index a1d52b28ed5..1583564522e 100644
--- a/doc/whats-new.rst
+++ b/doc/whats-new.rst
@@ -105,6 +105,8 @@ Bug fixes
 - Fix bug in time parsing failing to fall back to cftime. This was causing time
   variables with a time unit of `'msecs'` to fail to parse. (:pull:`3998`)
   By `Ryan May <https://github.com/dopplershift>`_.
+- Fix html repr in untrusted notebooks: fallback to plain text repr. (:pull:`4053`)
+  By `Benoit Bovy <https://github.com/benbovy>`_.
 
 Documentation
 ~~~~~~~~~~~~~
diff --git a/xarray/core/formatting_html.py b/xarray/core/formatting_html.py
index 6e345582ed0..69832d6ca3d 100644
--- a/xarray/core/formatting_html.py
+++ b/xarray/core/formatting_html.py
@@ -222,14 +222,20 @@ def array_section(obj):
 )
 
 
-def _obj_repr(header_components, sections):
+def _obj_repr(obj, header_components, sections):
+    """Return HTML repr of an xarray object.
+
+    If CSS is not injected (untrusted notebook), fallback to the plain text repr.
+
+    """
     header = f"<div class='xr-header'>{''.join(h for h in header_components)}</div>"
     sections = "".join(f"<li class='xr-section-item'>{s}</li>" for s in sections)
 
     return (
         "<div>"
         f"{ICONS_SVG}<style>{CSS_STYLE}</style>"
-        "<div class='xr-wrap'>"
+        f"<pre class='xr-text-repr-fallback'>{escape(repr(obj))}</pre>"
+        "<div class='xr-wrap' hidden>"
         f"{header}"
         f"<ul class='xr-sections'>{sections}</ul>"
         "</div>"
@@ -257,7 +263,7 @@ def array_repr(arr):
 
     sections.append(attr_section(arr.attrs))
 
-    return _obj_repr(header_components, sections)
+    return _obj_repr(arr, header_components, sections)
 
 
 def dataset_repr(ds):
@@ -272,4 +278,4 @@ def dataset_repr(ds):
         attr_section(ds.attrs),
     ]
 
-    return _obj_repr(header_components, sections)
+    return _obj_repr(ds, header_components, sections)
diff --git a/xarray/static/css/style.css b/xarray/static/css/style.css
index acfe85d5ac7..39cd6d6755f 100644
--- a/xarray/static/css/style.css
+++ b/xarray/static/css/style.css
@@ -26,10 +26,16 @@ body.vscode-dark {
 }
 
 .xr-wrap {
+  display: block;
   min-width: 300px;
   max-width: 700px;
 }
 
+.xr-text-repr-fallback {
+  /* fallback to plain text repr when CSS is not injected (untrusted notebook) */
+  display: none;
+}
+
 .xr-header {
   padding-top: 6px;
   padding-bottom: 6px;
diff --git a/xarray/static/html/icons-svg-inline.html b/xarray/static/html/icons-svg-inline.html
index c44f89c4304..b0e837a26cd 100644
--- a/xarray/static/html/icons-svg-inline.html
+++ b/xarray/static/html/icons-svg-inline.html
@@ -1,13 +1,11 @@
 <svg style="position: absolute; width: 0; height: 0; overflow: hidden">
 <defs>
 <symbol id="icon-database" viewBox="0 0 32 32">
-<title>Show/Hide data repr</title>
 <path d="M16 0c-8.837 0-16 2.239-16 5v4c0 2.761 7.163 5 16 5s16-2.239 16-5v-4c0-2.761-7.163-5-16-5z"></path>
 <path d="M16 17c-8.837 0-16-2.239-16-5v6c0 2.761 7.163 5 16 5s16-2.239 16-5v-6c0 2.761-7.163 5-16 5z"></path>
 <path d="M16 26c-8.837 0-16-2.239-16-5v6c0 2.761 7.163 5 16 5s16-2.239 16-5v-6c0 2.761-7.163 5-16 5z"></path>
 </symbol>
 <symbol id="icon-file-text2" viewBox="0 0 32 32">
-<title>Show/Hide attributes</title>
 <path d="M28.681 7.159c-0.694-0.947-1.662-2.053-2.724-3.116s-2.169-2.030-3.116-2.724c-1.612-1.182-2.393-1.319-2.841-1.319h-15.5c-1.378 0-2.5 1.121-2.5 2.5v27c0 1.378 1.122 2.5 2.5 2.5h23c1.378 0 2.5-1.122 2.5-2.5v-19.5c0-0.448-0.137-1.23-1.319-2.841zM24.543 5.457c0.959 0.959 1.712 1.825 2.268 2.543h-4.811v-4.811c0.718 0.556 1.584 1.309 2.543 2.268zM28 29.5c0 0.271-0.229 0.5-0.5 0.5h-23c-0.271 0-0.5-0.229-0.5-0.5v-27c0-0.271 0.229-0.5 0.5-0.5 0 0 15.499-0 15.5 0v7c0 0.552 0.448 1 1 1h7v19.5z"></path>
 <path d="M23 26h-14c-0.552 0-1-0.448-1-1s0.448-1 1-1h14c0.552 0 1 0.448 1 1s-0.448 1-1 1z"></path>
 <path d="M23 22h-14c-0.552 0-1-0.448-1-1s0.448-1 1-1h14c0.552 0 1 0.448 1 1s-0.448 1-1 1z"></path>
diff --git a/xarray/tests/test_formatting_html.py b/xarray/tests/test_formatting_html.py
index 94653016416..90e74f1f78f 100644
--- a/xarray/tests/test_formatting_html.py
+++ b/xarray/tests/test_formatting_html.py
@@ -139,6 +139,13 @@ def test_repr_of_dataset(dataset):
     assert "&lt;IA&gt;" in formatted
 
 
+def test_repr_text_fallback(dataset):
+    formatted = fh.dataset_repr(dataset)
+
+    # Just test that the "pre" block used for fallback to plain text is present.
+    assert "<pre class='xr-text-repr-fallback'>" in formatted
+
+
 def test_variable_repr_html():
     v = xr.Variable(["time", "x"], [[1, 2, 3], [4, 5, 6]], {"foo": "bar"})
     assert hasattr(v, "_repr_html_")