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Previews are the recommended way to test changes before production.

Use Version URLs only when you need to inspect one specific uploaded version before deploying it to production traffic.

Version URLs are created from Worker versions, including versions uploaded with wrangler versions upload. They are tied to the Versions and Deployments workflow.

Version URLs are the right fit for:

• Inspecting one uploaded version before a production deployment or gradual deployment.
• Workflows built around wrangler versions upload and wrangler versions deploy.

If you are using aliased Version URLs created with wrangler versions upload --preview-alias for branch or pull request previews, switch to Previews instead. Aliased Version URLs do not create branch-isolated resources.

Previews give you branch isolation, Preview-specific settings, custom domain support, and automatic resource isolation for Durable Objects and Containers.

Wrangler environments create separately named Workers, such as my-worker-staging. Use them when development, staging, or other environments need persistent Workers with different settings, routes, or custom domains.

You can create branch Previews under a Wrangler environment. Define its Preview settings in env.staging.previews:

{
  "name": "my-worker",
  "env": {
    "dev": {
      "name": "my-worker-dev",
      "vars": {
        "ENVIRONMENT": "development"
      }
    },
    "staging": {
      "name": "my-worker-staging",
      "vars": {
        "ENVIRONMENT": "staging"
      },
      "previews": {
        "vars": {
          "ENVIRONMENT": "staging-preview"
        }
      }
    }
  }
}

name = "my-worker"

[env.dev]
name = "my-worker-dev"

  [env.dev.vars]
  ENVIRONMENT = "development"

[env.staging]
name = "my-worker-staging"

  [env.staging.vars]
  ENVIRONMENT = "staging"

[env.staging.previews.vars]
ENVIRONMENT = "staging-preview"

In this example, dev has no previews block and remains a persistent Worker environment. staging includes a previews block for branch Previews.

Then include the environment when you run the Preview command:

npx wrangler preview --env staging

This creates or updates the branch Preview under the staging Worker. The Wrangler environment provides the persistent boundary, and Previews provide branch isolation within it.