1 files changed, 2 insertions, 0 deletions

diff --git a/tools/recovery_l10n/README.md b/tools/recovery_l10n/README.md
index bf41ff241..1554f6618 100644
--- a/tools/recovery_l10n/README.md
+++ b/tools/recovery_l10n/README.md
@@ -25,6 +25,8 @@
     *   "pngcrush -c 0 ..." converts "text-out.png" into a 1-channel image,
         which is accepted by Recovery. This also compresses the image file by
         ~60%.
+    *   zopflipng could further compress the png files by ~10%, more details
+        in https://github.com/google/zopfli/blob/master/README.zopflipng
     *   If you're using other png compression tools, make sure the final text
         image works by running graphic tests under the recovery mode.