Diff Strategies

Argo CD calculates the diff between the desired state and the live state in order to define if an Application is out-of-sync. This same logic is also used in Argo CD UI to display the differences between live and desired states for all resources belonging to an application.

Argo CD currently has 3 different strategies to calculate diffs:

• Legacy: This is the main diff strategy used by default. It applies a 3-way diff based on live state, desired state and last-applied-configuration (annotation).
• Structured-Merge Diff: Discontinued strategy that was previously applied when enabling the Server-Side Apply sync option. It has been superseded by Server-Side Diff.
• Server-Side Diff: Strategy that invokes a Server-Side Apply in dryrun mode in order to generate the predicted live state. It is used automatically when the Server-Side Apply sync option is enabled.

Structured-Merge Diff

Warning

Feature Discontinued

After different issues were identified by the community, this strategy has been discontinued in favour of Server-Side Diff.

This diff strategy was previously used automatically when the Server-Side Apply sync option was enabled. Enabling Server-Side Apply now uses Server-Side Diff instead. This strategy used the structured-merge-diff library used by Kubernetes to calculate diffs based on fields ownership. There were some challenges using this strategy to calculate diffs for CRDs that define default values.

Server-Side Diff

Current Status: Stable (Since v3.1.0)

Server-Side Diff is used automatically for Applications that enable the Server-Side Apply sync option, as it most accurately predicts the result of a server-side apply. This can be overridden by explicitly setting the argocd.argoproj.io/compare-options: ServerSideDiff=false annotation, in which case the Application falls back to the Legacy (client-side) diff.

This diff strategy will execute a Server-Side Apply in dryrun mode for each resource of the application. The response of this operation is then compared with the live state in order to provide the diff results. The diff results are cached and new Server-Side Apply requests to Kube API are only triggered when:

• An Application refresh or hard-refresh is requested.
• There is a new revision in the repo which the Argo CD Application is targeting.
• The Argo CD Application spec changed.
• The Resource Version of the resource itself in live state changed

One advantage of Server-Side Diff is that Kubernetes Admission Controllers will participate in the diff calculation. If for example a validation webhook identifies a resource to be invalid, that will be informed to Argo CD during the diff stage rather than during the sync stage.

Note that Server-Side Diff will not be performed during the creation of new resources. This is to save an additional call to KubeAPI and provide a much lighter and faster diff calculation (Non-Server-Side Apply) when resources don't exist to compare against. During resource creation performing a Server-Side Diff won't have the benefit of the Kubernetes Admission Controller in the diff stage as validation webhooks won't be executed when calculating diffs if the resource is not applied in the cluster yet.

Enabling it

Server-Side Diff can be enabled at the Argo CD Controller level or per Application.

Enabling Server-Side Diff for all Applications

Add the following entry in the argocd-cmd-params-cm configmap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: argocd-cmd-params-cm
data:
  controller.diff.server.side: "true"
...

Note: It is necessary to restart the argocd-application-controller after applying this configuration.

Enabling Server-Side Diff for one application

Add the following annotation in the Argo CD Application resource:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  annotations:
    argocd.argoproj.io/compare-options: ServerSideDiff=true
...

Disabling Server-Side Diff for one application

If Server-Side Diff is enabled globally in your Argo CD instance, it is possible to disable it at the application level. In order to do so, add the following annotation in the Application resource:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  annotations:
    argocd.argoproj.io/compare-options: ServerSideDiff=false
...

Note: Please report any issues that forced you to disable the Server-Side Diff feature

Local diff with server-side generation

argocd app diff supports a --local flag that compares a local directory against the live state. When combined with --server-side-generate, the CLI uploads the local source to the repo-server for manifest generation instead of running generation locally — this is useful in CI pipelines or when the local environment lacks the required tools (e.g. Helm plugins, Kustomize components).

argocd app diff my-app --local ./path --server-side-generate

Controlling which files are uploaded with --local-include

By default, the CLI sends files matching *.yaml, *.yml, *.json, *.tpl, and Chart.lock. You can override this with --local-include:

• Patterns without a path separator (e.g. *.yaml, *.tpl) match on the filename alone, regardless of directory depth.
• Patterns with a path separator (e.g. charts/**) match against the relative path and support ** to span multiple directory levels.

Warning

--local-include replaces the default set entirely. Re-specify any defaults you want to keep alongside your custom patterns.

Note

Kustomize apps that reference non-YAML source files in configMapGenerator or secretGenerator (e.g. *.env, *.properties) must add those patterns explicitly — no generic default covers all possible filenames and extensions.

Examples:

# Include all files under charts/ (e.g. when charts/ contains non-YAML assets)
argocd app diff my-app --local ./path --server-side-generate \
  --local-include "*.yaml" --local-include "*.yml" --local-include "*.json" \
  --local-include "*.tpl" --local-include "Chart.lock" \
  --local-include "charts/**"

# Add non-YAML Kustomize source files (e.g. configMapGenerator env files)
argocd app diff my-app --local ./path --server-side-generate \
  --local-include "*.yaml" --local-include "*.yml" --local-include "*.json" \
  --local-include "*.tpl" --local-include "Chart.lock" \
  --local-include "*.env"

Mutation Webhooks

Server-Side Diff does not include changes made by mutation webhooks by default. If you want to include mutation webhooks in Argo CD diffs add the following annotation in the Argo CD Application resource:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  annotations:
    argocd.argoproj.io/compare-options: IncludeMutationWebhook=true
...

Note: This annotation is only effective when Server-Side Diff is enabled. To enable both options for a given application add the following annotation in the Argo CD Application resource:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  annotations:
    argocd.argoproj.io/compare-options: ServerSideDiff=true,IncludeMutationWebhook=true
...