diff --git a/misc/userscripts/format_json b/misc/userscripts/format_json
index 10ff23e53..0d476b327 100755
--- a/misc/userscripts/format_json
+++ b/misc/userscripts/format_json
@@ -1,4 +1,5 @@
 #!/bin/sh
+set -euo pipefail
 #
 # Behavior:
 #   Userscript for qutebrowser which will take the raw JSON text of the current
@@ -19,28 +20,23 @@
 #
 # Bryan Gilbert, 2017
 
+# do not run pygmentize on files larger than this amount of bytes
+MAX_SIZE_PRETTIFY=10485760  # 10 MB
 # default style to monokai if none is provided
 STYLE=${1:-monokai}
-# format json using jq
-if ! FORMATTED_JSON="$(jq . "$QUTE_TEXT")" ||  [ -z "$FORMATTED_JSON" ]; then
-    echo "Invalid json, aborting..."
-    exit 1
+
+TEMP_FILE="$(mktemp)"
+jq . "$QUTE_TEXT" >"$TEMP_FILE"
+
+# try GNU stat first and then OSX stat if the former fails
+FILE_SIZE=$(
+  stat --printf="%s" "$TEMP_FILE" 2>/dev/null ||
+  stat -f%z "$TEMP_FILE" 2>/dev/null
+)
+if [ "$FILE_SIZE" -lt "$MAX_SIZE_PRETTIFY" ]; then
+    pygmentize -l json -f html -O full,style="$STYLE" <"$TEMP_FILE" >"${TEMP_FILE}_"
+    mv -f "${TEMP_FILE}_" "$TEMP_FILE"
 fi
 
-# calculate the filesize of the json document
-# parsing the output of ls should be fine in this case since we set the block size
-# shellcheck disable=SC2012
-FILE_SIZE=$(ls -s --block-size=1048576 "$QUTE_TEXT" | cut -d' ' -f1)
-
-# use pygments to pretty-up the json (syntax highlight) if file is less than 10MB
-if [ "$FILE_SIZE" -lt "10" ]; then
-    FORMATTED_JSON="$(echo "$FORMATTED_JSON" | pygmentize -l json -f html -O full,style="$STYLE")"
-fi
-
-# create a temp file and write the formatted json to that file
-TEMP_FILE="$(mktemp --suffix '.html')"
-echo "$FORMATTED_JSON" > "$TEMP_FILE"
-
-
 # send the command to qutebrowser to open the new file containing the formatted json
 echo "open -t file://$TEMP_FILE" >> "$QUTE_FIFO"