diff --git a/docs/.pages b/docs/.pages
index dfc7744e..f23b598a 100644
--- a/docs/.pages
+++ b/docs/.pages
@@ -1,4 +1,5 @@
 arrange:
 - index.md
 - ...
+- migrate-v3-to-v4.md
 - CONTRIBUTING.md
diff --git a/docs/migrate-v3-to-v4.md b/docs/migrate-v3-to-v4.md
new file mode 100644
index 00000000..eb7a63cd
--- /dev/null
+++ b/docs/migrate-v3-to-v4.md
@@ -0,0 +1,146 @@
+# Migrate from v3 to v4
+
+Several breaking changes have been done during this release on the configuration:
+
+- Targets
+- Templates structure and naming
+- TargetTemplates structure and naming
+- Default template names
+- Index document
+
+Those changes have been made in order to have a better merge feature on the configuration, for new features and to keep things in sync and organized.
+
+Here is a diff of the configuration with highlighted keys you will have to change during the upgrade:
+
+```diff linenums="1"
+ # Template configurations
+ # templates:
+-#   badRequest: templates/bad-request.tpl
+-#   folderList: templates/folder-list.tpl
+-#   forbidden: templates/forbidden.tpl
+-#   internalServerError: templates/internal-server-error.tpl
+-#   notFound: templates/not-found.tpl
+-#   targetList: templates/target-list.tpl
+-#   unauthorized: templates/unauthorized.tpl
++#   helpers:
++#     - templates/_helpers.tpl
++#   targetList:
++#     path: templates/target-list.tpl
++#     headers:
++#       Content-Type: '{{ template "main.headers.contentType" . }}'
++#   folderList:
++#     path: templates/folder-list.tpl
++#     headers:
++#       Content-Type: '{{ template "main.headers.contentType" . }}'
++#   badRequestError:
++#     path: templates/bad-request-error.tpl
++#     headers:
++#       Content-Type: '{{ template "main.headers.contentType" . }}'
++#   forbiddenError:
++#     path: templates/forbidden-error.tpl
++#     headers:
++#       Content-Type: '{{ template "main.headers.contentType" . }}'
++#   internalServerError:
++#     path: templates/internal-server-error.tpl
++#     headers:
++#       Content-Type: '{{ template "main.headers.contentType" . }}'
++#   notFoundError:
++#     path: templates/not-found-error.tpl
++#     headers:
++#       Content-Type: '{{ template "main.headers.contentType" . }}'
++#   unauthorizedError:
++#     path: templates/unauthorized-error.tpl
++#     headers:
++#       Content-Type: '{{ template "main.headers.contentType" . }}'
+
+ # Authentication Providers
+ # authProviders:
+@@ -136,9 +159,9 @@ log:
+ #           password:
+ #             path: password1-in-file
+
+-# Targets
++# Targets map
+ targets:
+-  - name: first-bucket
++  first-bucket:
+     ## Mount point
+     mount:
+       path:
+@@ -189,18 +212,20 @@ targets:
+     #       authorizationOPAServer:
+     #         # OPA server url with data path
+     #         url: http://localhost:8181/v1/data/example/authz/allowed
+-    # ## DEPRECATED Index document to display if exists in folder
+-    # indexDocument: index.html
+     # ## Actions
+     # actions:
+     #   # Action for GET requests on target
+     #   GET:
+     #     # Will allow GET requests
+     #     enabled: true
+-    #     # Redirect with trailing slash when a file isn't found
+-    #     redirectWithTrailingSlashForNotFoundFile: true
+-    #     # Index document to display if exists in folder
+-    #     indexDocument: index.html
++    #     # Configuration for GET requests
++    #     config:
++    #       # Redirect with trailing slash when a file isn't found
++    #       redirectWithTrailingSlashForNotFoundFile: true
++    #       # Index document to display if exists in folder
++    #       indexDocument: index.html
++    #       # Allow to add headers to streamed files (can be templated)
++    #       streamedFileHeaders: {}
+     #   # Action for PUT requests on target
+     #   PUT:
+     #     # Will allow PUT requests
+@@ -229,30 +254,40 @@ targets:
+     #     target: /$two/$one/$three/$one/
+     ## Target custom templates
+     # templates:
++    #   # Helpers
++    #   helpers:
++    #   - inBucket: false
++    #     path: ""
+     #   # Folder list template
+     #   folderList:
+     #     inBucket: false
+     #     path: ""
+-    #   # Not found template
+-    #   notFound:
++    #     headers: {}
++    #   # Not found error template
++    #   notFoundError:
+     #     inBucket: false
+     #     path: ""
++    #     headers: {}
+     #   # Internal server error template
+     #   internalServerError:
+     #     inBucket: false
+     #     path: ""
+-    #   # Forbidden template
+-    #   forbidden:
++    #     headers: {}
++    #   # Forbidden error template
++    #   forbiddenError:
+     #     inBucket: false
+     #     path: ""
+-    #   # Unauthorized template
+-    #   unauthorized:
++    #     headers: {}
++    #   # Unauthorized error template
++    #   unauthorizedError:
+     #     inBucket: false
+     #     path: ""
+-    #   # BadRequest template
+-    #   badRequest:
++    #     headers: {}
++    #   # Bad Request error template
++    #   badRequestError:
+     #     inBucket: false
+     #     path: ""
++    #     headers: {}
+     ## Bucket configuration
+     bucket:
+       name: super-bucket
+```