diff --git a/examples/pdf-invert-images.cc b/examples/pdf-invert-images.cc
index 4ec83b84..d3037984 100644
--- a/examples/pdf-invert-images.cc
+++ b/examples/pdf-invert-images.cc
@@ -15,8 +15,7 @@ void
 usage()
 {
     std::cerr << "Usage: " << whoami << " infile.pdf outfile.pdf [in-password]" << std::endl
-              << "Invert some images in infile.pdf;"
-              << " write output to outfile.pdf" << std::endl;
+              << "Invert some images in infile.pdf; write output to outfile.pdf" << std::endl;
     exit(2);
 }
 
diff --git a/examples/pdf-overlay-page.cc b/examples/pdf-overlay-page.cc
index 75577094..97ee8024 100644
--- a/examples/pdf-overlay-page.cc
+++ b/examples/pdf-overlay-page.cc
@@ -16,8 +16,8 @@ void
 usage()
 {
     std::cerr << "Usage: " << whoami << " infile pagefile outfile" << std::endl
-              << "Stamp page 1 of pagefile on every page of infile,"
-              << " writing to outfile" << std::endl;
+              << "Stamp page 1 of pagefile on every page of infile, writing to outfile"
+              << std::endl;
     exit(2);
 }
 
diff --git a/examples/qpdf-job.cc b/examples/qpdf-job.cc
index 99b853ea..3e6e99bd 100644
--- a/examples/qpdf-job.cc
+++ b/examples/qpdf-job.cc
@@ -11,10 +11,10 @@ static void
 usage()
 {
     std::cerr << "Usage: " << whoami << std::endl
-              << "This program linearizes the first page of in.pdf to out1.pdf,"
-              << " out2.pdf, and" << std::endl
-              << " out3.pdf, each demonstrating a different way to use the"
-              << " QPDFJob API" << std::endl;
+              << "This program linearizes the first page of in.pdf to out1.pdf, out2.pdf, and"
+              << std::endl
+              << " out3.pdf, each demonstrating a different way to use the QPDFJob API"
+              << std::endl;
     exit(2);
 }
 
@@ -43,7 +43,7 @@ main(int argc, char* argv[])
             ->pageSpec(".", "1")
             ->endPages()
             ->linearize()
-            ->staticId() // for testing only
+            ->staticId()           // for testing only
             ->compressStreams("n") // avoid dependency on zlib output
             ->checkConfiguration();
         j.run();
diff --git a/examples/qpdfjob-c.c b/examples/qpdfjob-c.c
index 6dd68283..e4f6fdf1 100644
--- a/examples/qpdfjob-c.c
+++ b/examples/qpdfjob-c.c
@@ -42,7 +42,7 @@ main(int argc, char* argv[])
     new_argv[1] = infile;
     new_argv[2] = outfile;
     new_argv[3] = "--linearize";
-    new_argv[4] = "--static-id"; /* for testing only */
+    new_argv[4] = "--static-id";          /* for testing only */
     new_argv[5] = "--compress-streams=n"; /* avoid dependency on zlib output */
     new_argv[6] = NULL;
 
diff --git a/format-code b/format-code
index 295c5d05..b2e72364 100755
--- a/format-code
+++ b/format-code
@@ -23,7 +23,7 @@
 # are improvements, bump the minimum required version of clang-format
 # here, and update manual/contributing.rst. There's a comment there
 # that refers to this comment. See also .clang-format.
-min_version=16
+min_version=18
 
 clang_version=$(clang-format --version | \
     awk '{for (i=1; i<=NF; i++) if ($i == "version") {print int($(i+1)); exit}}')
diff --git a/include/qpdf/QPDF.hh b/include/qpdf/QPDF.hh
index 392a153a..0d8b5f91 100644
--- a/include/qpdf/QPDF.hh
+++ b/include/qpdf/QPDF.hh
@@ -748,7 +748,8 @@ class QPDF
             int& O,
             bool compressed)
         {
-            return qpdf.generateHintStream(xref, lengths, obj_renumber, hint_stream, S, O, compressed);
+            return qpdf.generateHintStream(
+                xref, lengths, obj_renumber, hint_stream, S, O, compressed);
         }
 
         static void
diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index f6badc35..af3db080 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -2423,8 +2423,7 @@ QPDF::pipeStreamData(
         file->seek(offset, SEEK_SET);
         auto buf = std::make_unique<char[]>(length);
         if (auto read = file->read(buf.get(), length); read != length) {
-            throw damagedPDF(
-                file, "", offset + toO(read), "unexpected EOF reading stream data");
+            throw damagedPDF(file, "", offset + toO(read), "unexpected EOF reading stream data");
         }
         pipeline->write(buf.get(), length);
         attempted_finish = true;
@@ -2463,7 +2462,7 @@ QPDF::pipeStreamData(
             // ignore
         }
     }
-    return false ;
+    return false;
 }
 
 bool
diff --git a/libqpdf/QPDFJob.cc b/libqpdf/QPDFJob.cc
index 5296b7b3..ad186e13 100644
--- a/libqpdf/QPDFJob.cc
+++ b/libqpdf/QPDFJob.cc
@@ -3018,10 +3018,9 @@ QPDFJob::writeOutfile(QPDF& pdf)
             try {
                 QUtil::remove_file(backup.c_str());
             } catch (QPDFSystemError& e) {
-                *m->log->getError()
-                    << m->message_prefix << ": unable to delete original file (" << e.what() << ");"
-                    << " original file left in " << backup
-                    << ", but the input was successfully replaced\n";
+                *m->log->getError() << m->message_prefix << ": unable to delete original file ("
+                                    << e.what() << ");" << " original file left in " << backup
+                                    << ", but the input was successfully replaced\n";
             }
         }
     }
diff --git a/libqpdf/QPDFPageObjectHelper.cc b/libqpdf/QPDFPageObjectHelper.cc
index 54bb5cac..c250db8e 100644
--- a/libqpdf/QPDFPageObjectHelper.cc
+++ b/libqpdf/QPDFPageObjectHelper.cc
@@ -178,8 +178,8 @@ InlineImageTracker::handleToken(QPDFTokenizer::Token const& token)
                 QPDFObjectHandle dict = convertIIDict(QPDFObjectHandle::parse(dict_str));
                 dict.replaceKey("/Length", QPDFObjectHandle::newInteger(QIntC::to_longlong(len)));
                 std::string name = resources.getUniqueResourceName("/IIm", this->min_suffix);
-                QPDFObjectHandle image =
-                    QPDFObjectHandle::newStream(this->qpdf, std::make_shared<Buffer>(std::move(image_data)));
+                QPDFObjectHandle image = QPDFObjectHandle::newStream(
+                    this->qpdf, std::make_shared<Buffer>(std::move(image_data)));
                 image.replaceDict(dict);
                 resources.getKey("/XObject").replaceKey(name, image);
                 write(name);
diff --git a/libtests/bits.cc b/libtests/bits.cc
index 96c9ff02..bba1fd40 100644
--- a/libtests/bits.cc
+++ b/libtests/bits.cc
@@ -15,8 +15,7 @@
 static void
 print_values(long long byte_offset, size_t bit_offset, size_t bits_available)
 {
-    std::cout << "byte offset = " << byte_offset << ", "
-              << "bit offset = " << bit_offset << ", "
+    std::cout << "byte offset = " << byte_offset << ", " << "bit offset = " << bit_offset << ", "
               << "bits available = " << bits_available << std::endl;
 }
 
diff --git a/manual/contributing.rst b/manual/contributing.rst
index e0565872..d54378b0 100644
--- a/manual/contributing.rst
+++ b/manual/contributing.rst
@@ -27,7 +27,7 @@ The qpdf source code is formatted using clang-format with a
 :file:`.clang-format` file at the top of the source tree. The
 :file:`format-code` script reformats all the source code in the
 repository. You must have ``clang-format`` in your path, and it must
-be at least version 16.
+be at least version 18.
 
 For emacs users, the :file:`.dir-locals.el` file configures emacs
 ``cc-mode`` for an indentation style that is similar to but not
diff --git a/qpdf/fix-qdf.cc b/qpdf/fix-qdf.cc
index 5a399b48..510bb462 100644
--- a/qpdf/fix-qdf.cc
+++ b/qpdf/fix-qdf.cc
@@ -167,8 +167,7 @@ QdfFixer::processLines(std::string const& input)
                 xref_size = 1 + xref.size();
                 auto length = xref_size * esize;
                 std::cout << "  /Length " << length << "\n"
-                          << "  /W [ 1 " << xref_f1_nbytes << " " << xref_f2_nbytes << " ]"
-                          << "\n";
+                          << "  /W [ 1 " << xref_f1_nbytes << " " << xref_f2_nbytes << " ]\n";
                 state = st_in_xref_stream_dict;
             }
         } else if (state == st_in_ostream_dict) {
diff --git a/zlib-flate/zlib-flate.cc b/zlib-flate/zlib-flate.cc
index 1b1743b0..198ef07b 100644
--- a/zlib-flate/zlib-flate.cc
+++ b/zlib-flate/zlib-flate.cc
@@ -15,10 +15,9 @@ void
 usage()
 {
     std::cerr << "Usage: " << whoami << " { -uncompress | -compress[=n] }" << std::endl
-              << "If n is specified with -compress, it is a"
-              << " zlib compression level from" << std::endl
-              << "1 to 9 where lower numbers are faster and"
-              << " less compressed and higher" << std::endl
+              << "If n is specified with -compress, it is a zlib compression level from"
+              << std::endl
+              << "1 to 9 where lower numbers are faster and less compressed and higher" << std::endl
               << "numbers are slower and more compressed" << std::endl;
     exit(2);
 }