diff --git a/.github/workflows/draftrelease.yml b/.github/workflows/draftrelease.yml
index a7148ea..60662fc 100644
--- a/.github/workflows/draftrelease.yml
+++ b/.github/workflows/draftrelease.yml
@@ -59,6 +59,8 @@ jobs:
       run: for file in ./build/libs/*.jar; do ./ci-tools/ect-ubuntu-x86-64 -90032 --disable-png --disable-jpg -strip -zip $file; done
     - name: Run ECT (-9999) on built .jar files
       run: for file in ./build/libs/*.jar; do ./ci-tools/ect-ubuntu-x86-64 -9999 --disable-png --disable-jpg -strip -zip $file; done
+    - name: Run JarTighten on built .jar files
+      run: for file in ./build/libs/*.jar; do java -jar ./ci-tools/JarTighten-1.2.6-all.jar -o -c -E -S -t -z -j --mode=EXTENSIVE --zopfli-iter=9999 --optimise-existing-streams --optimise-recompressed-streams --compare-size-bits $file $file; done
     - name: Draft release
       uses: softprops/action-gh-release@v1
       with:
diff --git a/.github/workflows/gradle.yml b/.github/workflows/gradle.yml
index a5851e0..695c685 100644
--- a/.github/workflows/gradle.yml
+++ b/.github/workflows/gradle.yml
@@ -56,6 +56,8 @@ jobs:
       run: for file in ./build/libs/*.jar; do ./ci-tools/ect-ubuntu-x86-64 -30060 --disable-png --disable-jpg -strip -zip $file; done
     - name: Run ECT (-90032) on built .jar files
       run: for file in ./build/libs/*.jar; do ./ci-tools/ect-ubuntu-x86-64 -90032 --disable-png --disable-jpg -strip -zip $file; done
+    - name: Run JarTighten on built .jar files
+      run: for file in ./build/libs/*.jar; do java -jar ./ci-tools/JarTighten-1.2.6-all.jar -o -c -E -S -t -z -j --mode=MULTI_CHEAP --zopfli-iter=99 $file $file; done
     - name: Upload artifacts
       uses: actions/upload-artifact@v3
       with:
diff --git a/ci-tools/JarTighten-1.2.6-all.jar b/ci-tools/JarTighten-1.2.6-all.jar
new file mode 100644
index 0000000..9d15779
Binary files /dev/null and b/ci-tools/JarTighten-1.2.6-all.jar differ
diff --git a/ci-tools/README.md b/ci-tools/README.md
index f6294ee..b309a70 100644
--- a/ci-tools/README.md
+++ b/ci-tools/README.md
@@ -1,3 +1,4 @@
 # Programs used during CI builds
 
 - [ECT](https://github.com/fhanau/Efficient-Compression-Tool) - Efficient Compression Tool (or ECT) is a C++ file optimizer. This build of ECT was from commit 7249d5c (close to 0.9.4). Licensed under the Apache-2.0 license (see ECT-License.txt).
+- [JarTighten](https://github.com/NeRdTheNed/JarTighten) - Jar file size optimiser.