wrangler local R2 development adds experimental S3-compatible credentials

Introduced 2026-07-28 · score 0.91

HOW TO USE IT

For local development against an R2 bucket through the S3-compatible API, set `local_dev.experimental_s3_credentials` under its `r2_buckets` entry, with both credential fields. The local endpoint uses AWS SigV4; its bucket ID is `bucket_name`, or `binding` if `bucket_name` is unset.

{
  "r2_buckets": [
    {
      "binding": "<BINDING_NAME>",
      "bucket_name": "<BUCKET_NAME>",
      "local_dev": {
        "experimental_s3_credentials": {
          "accessKeyId": "<ACCESS_KEY_ID>",
          "secretAccessKey": "<SECRET_ACCESS_KEY>"
        }
      }
    }
  ]
}

WHY THIS HELPS

For local development against an R2 bucket through an S3-compatible API, configure the bucket's local development credentials.

REQUIREMENTS AND LIMITATIONS

Version: 4.115.0
Availability: Experimental.
r2_buckets[].binding (required): Binding name for the R2 bucket; used as the bucket ID if `bucket_name` is unset.
r2_buckets[].bucket_name (required): R2 bucket name; used as the local endpoint bucket ID when set.
r2_buckets[].local_dev.experimental_s3_credentials: Enables local S3-compatible API credentials for this bucket.
accessKeyId (required): Configured AWS SigV4 access key ID.
secretAccessKey (required): Configured AWS SigV4 secret access key.
Prerequisite: The local API is available during local development at `/cdn-cgi/local/r2/s3/<bucket-id>` and authenticates with AWS SigV4 credentials.
The bucket is served through the S3-compatible API during local development.
The API is authenticated with the configured AWS SigV4 credentials.
`<bucket-id>` is the bucket's `bucket_name`, or the binding name if `bucket_name` is not set.
Docs conflict: The official PR page’s earlier configuration example uses a different field name and layout (`experimental_local_s3_credentials`); it conflicts with the Wrangler 4.115.0 release note’s `local_dev.experimental_s3_credentials`, so that PR example is not used here: https://github.com/cloudflare/workers-sdk/pull/14280

FIRST-PARTY EVIDENCE

Check the installed version and the source before using it. Entry JSON

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wrangler local R2 development adds experimental S3-compatible credentials