diff --git a/COPYING b/COPYING
index 2b034848..308d4cd7 100644
--- a/COPYING
+++ b/COPYING
@@ -31,7 +31,7 @@ include their complete licence notices in COPYING:
 * config/mkinstalldirs: Public domain.
 
 * configure: "unlimited permission to copy, distribute and modify"
-  from FSF, but this is also derived from configure.in, which is
+  from FSF, but this is also derived from configure.ac, which is
   GPLv2.
 
 * contrib/debian/rules: "GNU copyright 1997 to 1999 by Joey Hess",
diff --git a/INSTALL b/INSTALL
index 4c17001f..3c1528a0 100644
--- a/INSTALL
+++ b/INSTALL
@@ -24,7 +24,7 @@ ECMAScript (that's JavaScript) support.
 ./autogen.sh!  (It should be enough to do it once - however, if you have build
 problems, try running this first.) Also, you obviously need GNU make and
 autoconf installed on your system (for the supported versions of autoconf,
-see AC_PREREQ in configure.in).  Otherwise, you have to use the nightly GIT
+see AC_PREREQ in configure.ac).  Otherwise, you have to use the nightly GIT
 snapshot - you don't need to do this there.
 
 
diff --git a/Makefile b/Makefile
index effe97ba..b911c1ed 100644
--- a/Makefile
+++ b/Makefile
@@ -13,10 +13,10 @@ $(top_builddir)/config.status: $(top_srcdir)/configure
 	cd $(top_builddir) && $(SHELL) ./config.status --recheck
 
 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
-$(ACLOCAL_M4): $(top_srcdir)/configure.in
+$(ACLOCAL_M4): $(top_srcdir)/configure.ac
 	cd $(top_srcdir) && $(ACLOCAL)
 
-$(top_srcdir)/configure: $(top_srcdir)/configure.in $(ACLOCAL_M4)
+$(top_srcdir)/configure: $(top_srcdir)/configure.ac $(ACLOCAL_M4)
 	cd $(top_srcdir) && $(AUTOCONF)
 
 # Makefile.config doesn't need a separate timestamp file because
@@ -45,7 +45,7 @@ $(top_srcdir)/config.h.in: $(top_srcdir)/stamp-h.in
 		$(MAKE) $(top_srcdir)/stamp-h.in; \
 	else :; fi
 
-$(top_srcdir)/stamp-h.in: $(top_srcdir)/configure.in $(ACLOCAL_M4) 
+$(top_srcdir)/stamp-h.in: $(top_srcdir)/configure.ac $(ACLOCAL_M4) 
 	cd $(top_srcdir) && $(AUTOHEADER)
 	@echo timestamp > $(top_srcdir)/stamp-h.in 2> /dev/null
 
diff --git a/Makefile.config.in b/Makefile.config.in
index 30dea985..e0f61c2d 100644
--- a/Makefile.config.in
+++ b/Makefile.config.in
@@ -99,10 +99,10 @@ XMLTO = @XMLTO@
 X_CFLAGS = @X_CFLAGS@
 XGETTEXT = @XGETTEXT@
 
-#Warning: this one is not in configure.in so following line will not generate it
+#Warning: this one is not in configure.ac so following line will not generate it
 CONFIG_NLS = @CONFIG_NLS@
 
-# :r !grep '(CONFIG_[A-Z0-9_]\+[^A-Z0-9_]' configure.in | sed 's/^.*(\(CONFIG_[A-Z0-9_]\+\)[^A-Z0-9_].*$/\1 = @\1@/' | sort | uniq
+# :r !grep '(CONFIG_[A-Z0-9_]\+[^A-Z0-9_]' configure.ac | sed 's/^.*(\(CONFIG_[A-Z0-9_]\+\)[^A-Z0-9_].*$/\1 = @\1@/' | sort | uniq
 
 CONFIG_256_COLORS = @CONFIG_256_COLORS@
 CONFIG_88_COLORS = @CONFIG_88_COLORS@
diff --git a/configure.in b/configure.ac
similarity index 100%
rename from configure.in
rename to configure.ac
diff --git a/doc/Makefile b/doc/Makefile
index 2ba565fd..f31afa0d 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -209,7 +209,7 @@ elinks.conf.5.html: option-config.frag.xhtml
 perl-%.html: %.pl
 	$(call cmd,pod2html)
 
-Doxyfile: $(srcdir)Doxyfile.in $(top_srcdir)/configure.in
+Doxyfile: $(srcdir)Doxyfile.in $(top_srcdir)/configure.ac
 	cd $(top_builddir) && \
 	CONFIG_FILES="$(RELPATH)$@" CONFIG_HEADERS= $(SHELL) ./config.status
 
diff --git a/doc/man/man1/Makefile b/doc/man/man1/Makefile
index 56c1c077..b1e17178 100644
--- a/doc/man/man1/Makefile
+++ b/doc/man/man1/Makefile
@@ -1,7 +1,7 @@
 top_builddir=../../..
 include $(top_builddir)/Makefile.config
 
-elinks.1: $(srcdir)elinks.1.in $(top_srcdir)/configure.in
+elinks.1: $(srcdir)elinks.1.in $(top_srcdir)/configure.ac
 	cd $(top_builddir) && \
 	CONFIG_FILES="$(RELPATH)$@" CONFIG_HEADERS= $(SHELL) ./config.status
 
diff --git a/doc/release.txt b/doc/release.txt
index 2e05f85d..d054403c 100644
--- a/doc/release.txt
+++ b/doc/release.txt
@@ -11,7 +11,7 @@ When releasing a new version
    by new contributors are always important!
  - Update NEWS file and commit. Remember to add the new version number!
    Don't add the release date yet though; you will add it in a later step.
- - Change VERSION in the top of configure.in to hold the new version number.
+ - Change VERSION in the top of configure.ac to hold the new version number.
  - Update the manpages so the will have the new release number by first
    building the source, followed by making the `update-man' target in doc/.
  - Update po files by running `make update-po` in po/`.
@@ -34,7 +34,7 @@ When releasing a new version
 	$ gpg -b --armor elinks-X.X.X.tar.bz2
 	$ gpg -b --armor elinks-X.X.X.tar.gz
 
- - Append ".GIT" to the VERSION variable in the top of configure.in.
+ - Append ".GIT" to the VERSION variable in the top of configure.ac.
  - Commit only this change.
  - Push these changes plus tag using:
 
@@ -104,7 +104,7 @@ When releasing a new stable branch
  - Locally clone the freezed repository to a new repository that will contain
    the new stable branch.
  - Unfreeze the repository that was cloned by changing the VERSION variable in
-   configure.in to the version of the new unstable branch (remember the
+   configure.ac to the version of the new unstable branch (remember the
    ending ".GIT"), commit, and push.
  - Add new remote branch that will track the new stable "trunk". It should
    basically be the push URL of the cloned repository with "#elinks-X.X"
diff --git a/features.conf b/features.conf
index 7b0e2f43..ce7cf666 100644
--- a/features.conf
+++ b/features.conf
@@ -38,10 +38,10 @@
 # easier for us as well as for the users. Do not forget to accurately describe
 # the feature and also the impact of enabling/disabling it. Follow the format of
 # existing comments. Follow the example of XBEL when adding features which also
-# need some detection in configure.in.
+# need some detection in configure.ac.
 #
 # Not everything is suitable for an entry in this file, maybe it would be
-# happier directly in the configure.in. If it is really purely question of
+# happier directly in the configure.ac. If it is really purely question of
 # system support (X2, HAVE_SA_STORAGE), and it makes no sense for the user to
 # touch it, do not include it here.
 #
diff --git a/po/README b/po/README
index bf45e98c..d794c821 100644
--- a/po/README
+++ b/po/README
@@ -48,7 +48,7 @@ First change directory to the root directory of the unpacked source tarball:
 
 	$ cd ../
 
-Add your language code to the ALL_LINGUAS string in configure.in (keep the
+Add your language code to the ALL_LINGUAS string in configure.ac (keep the
 alphabetic order ;). To make the change take effect you have to rebuild all
 Makefiles:
 
diff --git a/src/intl/charsets.h b/src/intl/charsets.h
index 7c4df2a5..5b8fcb32 100644
--- a/src/intl/charsets.h
+++ b/src/intl/charsets.h
@@ -3,7 +3,7 @@
 
 struct hash;
 
-/* The TRE check in configure.in assumes unicode_val_T is uint32_t.  */
+/* The TRE check in configure.ac assumes unicode_val_T is uint32_t.  */
 typedef uint32_t unicode_val_T;
 
 /* U+0020 SPACE.  Normally the same as ' ' or L' ' but perhaps ELinks