diff --git a/.github/workflows/ci-mobile-save-for-later-user-deletion.yaml b/.github/workflows/ci-mobile-save-for-later-user-deletion.yaml
index 86e9b23b..c7885ab5 100644
--- a/.github/workflows/ci-mobile-save-for-later-user-deletion.yaml
+++ b/.github/workflows/ci-mobile-save-for-later-user-deletion.yaml
@@ -16,7 +16,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v3
         with:
-          java-version: 11
+          java-version: 21
           distribution: corretto
           cache: sbt
 
diff --git a/.github/workflows/ci-mobile-save-for-later.yaml b/.github/workflows/ci-mobile-save-for-later.yaml
index 02b2e3ea..2b00fa54 100644
--- a/.github/workflows/ci-mobile-save-for-later.yaml
+++ b/.github/workflows/ci-mobile-save-for-later.yaml
@@ -16,7 +16,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: 11
+          java-version: 21
           distribution: corretto
           cache: sbt
 
diff --git a/build.sbt b/build.sbt
index 45cba728..1103f923 100644
--- a/build.sbt
+++ b/build.sbt
@@ -67,7 +67,7 @@ val commonSettings: immutable.Seq[Def.Setting[_]] = List(
     "-deprecation",
     "-encoding",
     "UTF-8",
-    "-release:11",
+    "-release:21",
     "-Ypartial-unification",
     "-Ywarn-dead-code"
   )
diff --git a/cdk/lib/__snapshots__/mobile-save-for-later.test.ts.snap b/cdk/lib/__snapshots__/mobile-save-for-later.test.ts.snap
index ff990992..7f3a4d33 100644
--- a/cdk/lib/__snapshots__/mobile-save-for-later.test.ts.snap
+++ b/cdk/lib/__snapshots__/mobile-save-for-later.test.ts.snap
@@ -763,7 +763,7 @@ Object {
             "Arn",
           ],
         },
-        "Runtime": "java11",
+        "Runtime": "java21",
         "Tags": Array [
           Object {
             "Key": "App",
@@ -993,7 +993,7 @@ Object {
             "Arn",
           ],
         },
-        "Runtime": "java11",
+        "Runtime": "java21",
         "Tags": Array [
           Object {
             "Key": "App",
@@ -2029,7 +2029,7 @@ Object {
             "Arn",
           ],
         },
-        "Runtime": "java11",
+        "Runtime": "java21",
         "Tags": Array [
           Object {
             "Key": "App",
@@ -2259,7 +2259,7 @@ Object {
             "Arn",
           ],
         },
-        "Runtime": "java11",
+        "Runtime": "java21",
         "Tags": Array [
           Object {
             "Key": "App",
diff --git a/cdk/lib/mobile-save-for-later.ts b/cdk/lib/mobile-save-for-later.ts
index c0338b29..8757b127 100644
--- a/cdk/lib/mobile-save-for-later.ts
+++ b/cdk/lib/mobile-save-for-later.ts
@@ -41,7 +41,7 @@ export class MobileSaveForLater extends GuStack {
     const app = "mobile-save-for-later";
 
     const commonLambdaProps = {
-      runtime: Runtime.JAVA_11,
+      runtime: Runtime.JAVA_21,
       app,
       fileName: `${app}.jar`,
     };
diff --git a/docs/testing/save-for-later.md b/docs/testing/save-for-later.md
index 41c00271..8d8d3cb6 100644
--- a/docs/testing/save-for-later.md
+++ b/docs/testing/save-for-later.md
@@ -39,7 +39,8 @@
 
 ### Pre-requisites
 1) Mobile credentials from [Janus](https://janus.gutools.co.uk/login)
-2) Follow the authentication flow as outlined at the [top](#setting-up-oauth-flow)
+2) Make sure you have java 21 installed ([SDK man](https://sdkman.io/) is a good package manager)
+3) Follow the authentication flow as outlined at the [top](#setting-up-oauth-flow)
 
 * Go to `src/main/scala/com/gu/sfl/local/LocalServer.scala`
 * Select the drop down menu to the left of the run button and select `LocalServer` under run configurations
diff --git a/docs/testing/user-deletion.md b/docs/testing/user-deletion.md
index 92d21893..784451b3 100644
--- a/docs/testing/user-deletion.md
+++ b/docs/testing/user-deletion.md
@@ -36,6 +36,7 @@
 
 ### Pre-requisites
 1) Mobile credentials from [Janus](https://janus.gutools.co.uk/login)
+2) Make sure you have java 21 installed ([SDK man](https://sdkman.io/) is a good package manager)
 
 * Go to `src/main/scala/local/RunUserDeletionLambda.scala`
 * Select the drop down menu to the left of the run button and select `RunUserDeletionLambda` under run configurations
diff --git a/mobile-save-for-later-user-deletion/conf/cfn.yaml b/mobile-save-for-later-user-deletion/conf/cfn.yaml
index c2268248..12baed4e 100644
--- a/mobile-save-for-later-user-deletion/conf/cfn.yaml
+++ b/mobile-save-for-later-user-deletion/conf/cfn.yaml
@@ -149,7 +149,7 @@ Resources:
       Handler: com.gu.sfl.userdeletion.UserDeletionLambda::handler
       MemorySize: 512
       Role: !GetAtt UserDeletionRole.Arn
-      Runtime: java11
+      Runtime: java21
       Timeout: 300
   UserDeletionEventSource:
     Type: AWS::Lambda::EventSourceMapping