diff --git a/toys/README b/toys/README
new file mode 100644
index 0000000..e518275
--- /dev/null
+++ b/toys/README
@@ -0,0 +1,8 @@
+checkextensions
+===============
+Reports files whose extension does not match the (detected) mime-type.
+
+Options:
+	-u:	update source directory
+	-r:	rename files
+	-n:	(with -r): show what would be done.
diff --git a/toys/checkextensions b/toys/checkextensions
new file mode 100755
index 0000000..e68949c
--- /dev/null
+++ b/toys/checkextensions
@@ -0,0 +1,212 @@
+#!/bin/bash
+
+# config structures
+declare -A			\
+	destinationchannels	\
+	destinationfat32compat	\
+	destinationcopymime	\
+	destinationformat	\
+	destinationfrequency	\
+	destinationid		\
+	destinationloss		\
+	destinationmaxbps	\
+	destinationnormalize	\
+	destinationpath		\
+	destinationquality	\
+	destinationrename	\
+	destinationnoresample	\
+	destinationrenamepath	\
+	destinationskipmime	\
+|| {
+	echo "Check your Bash version. You need >= 4.0" >&2
+	exit $EBASHVERS
+}
+
+declare -r				\
+	DOCDIR=./doc			\
+	LIBDIR=./lib			\
+	SHAREDIR=./share
+declare -r				\
+	exampleconf=$DOCDIR/example.cfg	\
+	schema=$SHAREDIR/schema.sql	\
+					\
+	oldIFS="$IFS"
+
+LC_ALL=C
+
+shopt -s extglob
+
+for function in "$LIBDIR"/*/*
+do
+	source "$function"
+done
+
+while getopts 'urnD' opt
+do
+	case $opt in
+		u)	update=1	;;
+		r)	rename=1	;;
+		n)	pretend=1	;;
+		D)	(( debug++ ))	;;
+	esac
+done
+
+getConfig
+
+openDatabase
+
+(( update )) && getFiles
+
+echo '
+	SELECT
+		source_files.id,
+		source_files.filename,
+		mime_types.mime_text
+	FROM
+			source_files
+	INNER JOIN	mime_types
+		ON	source_files.mime_type = mime_types.id
+	;
+	SELECT	"AtOM:NoMoreFiles";
+' >&3
+
+getdstfiles() {
+	local		\
+		line	\
+		lines
+	unset dest
+	for destination in "${!destinationformat[@]}"
+	do
+		if [[ ${destinationformat["$destination"]} != $format ]]
+		then
+			continue
+		fi
+		echo '
+			SELECT
+				destination_files.id,
+				destination_files.filename
+			FROM		destination_files
+			INNER JOIN	source_files
+				ON
+				destination_files.source_file_id=source_files.id
+			INNER JOIN	destinations
+				ON
+				destinations.id=destination_files.destination_id
+			WHERE	source_files.id='$fileid'
+			AND	destinations.name="'"$destination"'"
+			AND	destination_files.filename IS NOT NULL
+			AND	destination_files.filename NOT LIKE
+					"%'$extension'"
+			;
+			SELECT	"AtOM:NoMoreFiles";
+		'>&3
+		while read -u4 line
+		do
+			if [[ $line == AtOM:NoMoreFiles ]]
+			then
+				break
+			fi
+			lines+=("$line")
+		done
+	done
+	for line in "${lines[@]}"
+	do
+		fileid=${line%|*}
+		filename=${line#*|}
+		echo $'\t'"$filename"
+		(( rename )) && echo -n $'\t'
+		(( rename )) && renameFile
+	done
+}
+
+renameFile() {
+	echo " -> ${filename%.*}$extension"
+	if ! (( pretend ))
+	then
+		if [[ $dest == '' ]]
+		then
+			table=destination_files
+		else
+			table=source_files
+		fi
+		mv							\
+			"${dest:+$dest/}$filename"			\
+			"${dest:+$dest/}${filename%.*}$extension"	\
+		&& Update $table filename "${filename%.*}$extension"<<-EOW
+			id = $fileid
+		EOW
+	fi
+}
+
+while read -u4 line
+do
+	if [[ $line == AtOM:NoMoreFiles ]]
+	then
+		break
+	fi
+	lines+=("$line")
+done
+for line in "${lines[@]}"
+do
+	fileid=${line%%|*}
+	rest="${line#*|}|"
+	filename=${rest%%|*}
+	rest=${rest#*|}
+	mimetype=${rest%%|*}
+	rest=${rest#*|}
+	dest=$sourcepath
+	case "$mimetype" in
+		'audio/mpeg')
+			if [[ ${filename##*.} != mp3 ]]
+			then
+				format=mp3
+				extension=.mp3
+				echo "$filename: MP3 ($extension)"
+				(( rename )) && renameFile
+				getdstfiles
+			fi
+		;;
+		'application/ogg vorbis')
+			if [[ ${filename##*.} != ogg ]]
+			then
+				format=vorbis
+				extension=.ogg
+				echo "$filename: Ogg Vorbis ($extension)"
+				(( rename )) && renameFile
+				getdstfiles
+			fi
+		;;
+		'application/ogg opus')
+			if [[ ${filename##*.} != opus ]]
+			then
+				format=opus
+				extension=.opus
+				echo "$filename: Opus ($extension)"
+				(( rename )) && renameFile
+				getdstfiles
+			fi
+		;;
+		'audio/x-flac')
+			if [[ ${filename##*.} != flac ]]
+			then
+				format=flac
+				extension=.flac
+				echo "$filename: FLAC ($extension)"
+				(( rename )) && renameFile
+			fi
+		;;
+		'application/data')
+			extendedtype=$(file -b "$sourcepath/$filename")
+			[[ $extendedtype =~ Musepack ]] || continue
+			if [[ ${filename##*.} != flac ]]
+			then
+				format=mpc
+				extension=.mpc
+				echo "$filename: Musepack ($extension)"
+				(( rename )) && renameFile
+			fi
+		;;
+	esac
+done
+
+closeDatabase