diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
new file mode 100644
index 00000000..a8a642c8
--- /dev/null
+++ b/.github/workflows/format.yml
@@ -0,0 +1,17 @@
+name: format
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  format:
+    name: format
+    runs-on: ubuntu-latest
+    container: ghcr.io/c-cube/c-cube-commmon/ci-4.14:latest
+
+    steps:
+      - uses: actions/checkout@v6
+      - run: opam exec -- make format-check
diff --git a/.github/workflows/gh-pages.yml b/.github/workflows/gh-pages.yml
index bb3f943d..539047a5 100644
--- a/.github/workflows/gh-pages.yml
+++ b/.github/workflows/gh-pages.yml
@@ -8,18 +8,13 @@ on:
 jobs:
   deploy:
     runs-on: ubuntu-latest
+    container: ghcr.io/c-cube/c-cube-commmon/ci-doc-5.3:latest
+
     steps:
-      - uses: actions/checkout@main
-        with:
-          submodules: 'recursive'
-      - uses: ocaml/setup-ocaml@v3
-        with:
-          ocaml-compiler: '5.2'
-          dune-cache: true
-          allow-prerelease-opam: true
+      - uses: actions/checkout@v6
 
       - name: Deps
-        run: opam install odig linol linol-lwt
+        run: opam install linol linol-lwt
 
       - name: Build
         run: opam exec -- odig odoc --cache-dir=_doc/ linol linol-lwt || (odig log -e ; exit 1)
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 20ad873d..f1c9c00f 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -6,52 +6,27 @@ on:
   pull_request:
 jobs:
   build4:
-    strategy:
-      matrix:
-        os:
-          - ubuntu-latest
-        ocaml-compiler:
-          - 4.14.x
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
+    container: ghcr.io/c-cube/c-cube-commmon/ci-4.14:latest
     steps:
-    - uses: actions/checkout@main
+    - uses: actions/checkout@v6
       with:
         submodules: 'recursive'
-    - uses: ocaml/setup-ocaml@v3
-      with:
-        ocaml-compiler: ${{ matrix.ocaml-compiler }}
-        dune-cache: true
-        allow-prerelease-opam: true
     - run: opam pin -n .
     - run: opam depext -yt linol linol-lwt
     - run: opam install linol linol-lwt --deps-only -t
     - run: opam exec -- dune build -p linol,linol-lwt
     - run: opam exec -- dune runtest -p linol,linol-lwt
-      if: ${{ matrix.os == 'ubuntu-latest'  }}
+
   build5:
-    strategy:
-      matrix:
-        os:
-          - ubuntu-latest
-          #- macos-latest
-          #- windows-latest
-        ocaml-compiler:
-          - 5.1.x
-          - 5.2.x
-          - 5.3.x
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
+    container: ghcr.io/c-cube/c-cube-commmon/ci-5.4:latest
     steps:
-    - uses: actions/checkout@main
+    - uses: actions/checkout@v6
       with:
-          submodules: 'recursive'
-    - uses: ocaml/setup-ocaml@v3
-      with:
-        ocaml-compiler: ${{ matrix.ocaml-compiler }}
-        dune-cache: true
-        allow-prerelease-opam: true
+        submodules: 'recursive'
     - run: opam pin -n .
     - run: opam depext -yt linol linol-lwt linol-eio
     - run: opam install -t . --deps-only
     - run: opam exec -- dune build
     - run: opam exec -- dune runtest
-      if: ${{ matrix.os == 'ubuntu-latest'  }}
diff --git a/Makefile b/Makefile
index 7c1430d9..00e2f5d9 100644
--- a/Makefile
+++ b/Makefile
@@ -13,9 +13,12 @@ clean:
 doc:
 	@dune build @doc
 
-fmt:
+format:
 	@dune build @fmt --auto-promote
 
+format-check:
+	@dune build $(DUNE_OPTS) @fmt --display=quiet
+
 update-submodules:
 	@git submodule update --init