diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
index bf186c191b04d1..2d4f7898e79b0c 100644
--- a/Doc/whatsnew/3.15.rst
+++ b/Doc/whatsnew/3.15.rst
@@ -89,6 +89,13 @@ New modules
Improved modules
================
+difflib
+-------
+
+* Improved the styling of HTML diff pages generated by the :class:`difflib.HtmlDiff`
+ class, and migrated the output to the HTML5 standard.
+ (Contributed by Jiahao Li in :gh:`134580`.)
+
ssl
---
diff --git a/Lib/difflib.py b/Lib/difflib.py
index f1f4e62514a7bd..18801a9b19eb9d 100644
--- a/Lib/difflib.py
+++ b/Lib/difflib.py
@@ -1615,16 +1615,13 @@ def _line_pair_iterator():
_file_template = """
-
-
-
-
+
+
-
-
-
@@ -1636,13 +1633,36 @@ def _line_pair_iterator():
_styles = """
:root {color-scheme: light dark}
- table.diff {font-family: Menlo, Consolas, Monaco, Liberation Mono, Lucida Console, monospace; border:medium}
- .diff_header {background-color:#e0e0e0}
- td.diff_header {text-align:right}
- .diff_next {background-color:#c0c0c0}
+ table.diff {
+ font-family: Menlo, Consolas, Monaco, Liberation Mono, Lucida Console, monospace;
+ border: medium;
+ }
+ .diff_header {
+ background-color: #e0e0e0;
+ font-weight: bold;
+ }
+ td.diff_header {
+ text-align: right;
+ padding: 0 8px;
+ }
+ .diff_next {
+ background-color: #c0c0c0;
+ padding: 4px 0;
+ }
.diff_add {background-color:palegreen}
.diff_chg {background-color:#ffff77}
.diff_sub {background-color:#ffaaaa}
+ table.diff[summary="Legends"] {
+ margin-top: 20px;
+ border: 1px solid #ccc;
+ }
+ table.diff[summary="Legends"] th {
+ background-color: #e0e0e0;
+ padding: 4px 8px;
+ }
+ table.diff[summary="Legends"] td {
+ padding: 4px 8px;
+ }
@media (prefers-color-scheme: dark) {
.diff_header {background-color:#666}
@@ -1650,6 +1670,8 @@ def _line_pair_iterator():
.diff_add {background-color:darkgreen}
.diff_chg {background-color:#847415}
.diff_sub {background-color:darkred}
+ table.diff[summary="Legends"] {border-color:#555}
+ table.diff[summary="Legends"] th{background-color:#666}
}"""
_table_template = """
@@ -1692,7 +1714,7 @@ class HtmlDiff(object):
make_table -- generates HTML for a single side by side table
make_file -- generates complete HTML file with a single side by side table
- See tools/scripts/diff.py for an example usage of this class.
+ See Doc/includes/diff.py for an example usage of this class.
"""
_file_template = _file_template
diff --git a/Lib/test/test_difflib.py b/Lib/test/test_difflib.py
index 9e217249be7332..6ac584a08d1e86 100644
--- a/Lib/test/test_difflib.py
+++ b/Lib/test/test_difflib.py
@@ -255,21 +255,21 @@ def test_make_file_default_charset(self):
html_diff = difflib.HtmlDiff()
output = html_diff.make_file(patch914575_from1.splitlines(),
patch914575_to1.splitlines())
- self.assertIn('content="text/html; charset=utf-8"', output)
+ self.assertIn('charset="utf-8"', output)
def test_make_file_iso88591_charset(self):
html_diff = difflib.HtmlDiff()
output = html_diff.make_file(patch914575_from1.splitlines(),
patch914575_to1.splitlines(),
charset='iso-8859-1')
- self.assertIn('content="text/html; charset=iso-8859-1"', output)
+ self.assertIn('charset="iso-8859-1"', output)
def test_make_file_usascii_charset_with_nonascii_input(self):
html_diff = difflib.HtmlDiff()
output = html_diff.make_file(patch914575_nonascii_from1.splitlines(),
patch914575_nonascii_to1.splitlines(),
charset='us-ascii')
- self.assertIn('content="text/html; charset=us-ascii"', output)
+ self.assertIn('charset="us-ascii"', output)
self.assertIn('ımplıcıt', output)
class TestDiffer(unittest.TestCase):
diff --git a/Lib/test/test_difflib_expect.html b/Lib/test/test_difflib_expect.html
index 9f33a9e9c9cf58..2346a6f9f8dddf 100644
--- a/Lib/test/test_difflib_expect.html
+++ b/Lib/test/test_difflib_expect.html
@@ -1,22 +1,42 @@
-
-
-
-
+
+
-
-
-
diff --git a/Misc/NEWS.d/next/Library/2025-05-23-20-01-52.gh-issue-134580.xnaJ70.rst b/Misc/NEWS.d/next/Library/2025-05-23-20-01-52.gh-issue-134580.xnaJ70.rst
new file mode 100644
index 00000000000000..979d310d3cee58
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-23-20-01-52.gh-issue-134580.xnaJ70.rst
@@ -0,0 +1,3 @@
+Improved the styling of HTML diff pages generated by the
+:class:`difflib.HtmlDiff` class, and migrated the output to the HTML5
+standard.