# atmos aws cloudformation diff

Create (or reuse) a CloudFormation changeset for the component and render the
predicted changes, without executing it. `diff` authenticates and calls the
CloudFormation API — it previews what `apply` would actually do to the live
stack, unlike [`render`](/cli/commands/aws/cloudformation/render), which never
leaves the local template.

> ⚠️ Experimental

## Usage

```shell
atmos aws cloudformation diff <component> --stack <stack> [options]
```

```shell
atmos aws cloudformation diff vpc -s plat-ue2-dev
```

Diff all or affected components in dependency order:

```shell
atmos aws cloudformation diff --all -s plat-ue2-dev
atmos aws cloudformation diff --affected --base origin/main
```

Diff components filtered by tags or labels (composes with `--all`/`--affected` to narrow the selected set further):

```shell
atmos aws cloudformation diff --all --tags production,tier-1
atmos aws cloudformation diff --affected --labels cost-center=platform
```

## Flags

- **`--stack`, `-s` (required for a single component)**
  Atmos stack. Required when operating on a single component; optional (and used only to narrow the selected set) with 
  `--all`
  /
  `--affected`
  .
- **`--all` (optional)**
  Diff all 
  `aws/cloudformation`
   components in dependency order.
- **`--affected` (optional)**
  Diff affected 
  `aws/cloudformation`
   components and their dependencies.
- **`--include-dependents` (optional)**
  With 
  `--affected`
  , include dependent 
  `aws/cloudformation`
   components.
- **`--base` (optional)**
  Git base ref or SHA to compare against for affected detection: 
  `--base origin/main`
  . Used with 
  `--affected`
  .
- **`--tags` (optional)**
  Filter by tags (comma-separated, matches any): 
  `--tags=production,tier-1`
  . Composes with 
  `--all`
  /
  `--affected`
   to narrow the selected set further; cannot be combined with a single component argument.
- **`--labels` (optional)**
  Filter by labels (comma-separated 
  `key=value`
   or 
  `key:value`
   pairs, matches all): 
  `--labels=cost-center=platform,compliance=sox`
  . Composes with 
  `--all`
  /
  `--affected`
  /
  `--tags`
  ; cannot be combined with a single component argument.

:::note
[`atmos aws cloudformation plan`](/cli/commands/aws/cloudformation/plan) is an alias for `diff`.
Both fire the `before.aws/cloudformation.diff`/`after.aws/cloudformation.diff` hook events.
:::