Extensions
R2 implements some extensions on top of the basic S3 API. This page outlines these additional, available features.
Extended metadata using Unicode
The Workers R2 API supports Unicode in keys and values natively without requiring any additional encoding or decoding for the customMetadata field. These fields map to the x-amz-meta--prefixed headers used within the R2 S3-compatible API endpoint.
HTTP header names and values may only contain ASCII characters, which is a small subset of the Unicode character library. To easily accommodate users, R2 adheres to RFC2047 and automatically decodes all x-amz-meta-* header values before storage. On retrieval, any metadata values with unicode are RFC2047-encoded before rendering the response. The length limit for metadata values is applied to the decoded Unicode value.
These headers map to the httpMetadata field in the R2 bindings:
| HTTP Header | Property Name |
|---|---|
Content-Encoding | httpMetadata.contentEncoding |
Content-Type | httpMetadata.contentType |
Content-Language | httpMetadata.contentLanguage |
Content-Disposition | httpMetadata.contentDisposition |
Cache-Control | httpMetadata.cacheControl |
Expires | httpMetadata.expires |
If using Unicode in object key names, refer to the Unicode Interoperability technical notes.
CopyObject
MERGE metadata directive
The x-amz-metadata-directive allows a MERGE value, in addition to the standard COPY and REPLACE options. When used, MERGE is a combination of COPY and REPLACE, which will COPY any metadata keys from the source object and REPLACE those that are specified in the request with the new value. You cannot use MERGE to remove existing metadata keys from the source — use REPLACE instead.
ListBuckets
ListBuckets supports all the same search parameters as ListObjectsV2 in R2 because some customers may have more than 1,000 buckets. Because tooling, like existing S3 libraries, may not expose a way to set these search parameters, these values may also be sent in via headers. Values in headers take precedence over the search parameters.
| Search parameter | HTTP Header | Meaning |
|---|---|---|
prefix | cf-prefix | Show buckets with this prefix only. |
start-after | cf-start-after | Show buckets whose name appears lexicographically in the account. |
continuation-token | cf-continuation-token | Resume listing from a previously returned continuation token. |
max-keys | cf-max-keys | Return this maximum number of buckets. Default and max is 1000. |
The XML response contains a NextContinuationToken and IsTruncated elements as appropriate. Since these may not be accessible from existing S3 APIs, these are also available in response headers:
| XML Response Element | HTTP Response Header | Meaning |
|---|---|---|
IsTruncated | cf-is-truncated | This is set to true if the list of buckets returned is not all the buckets on the account. |
NextContinuationToken | cf-next-continuation-token | This is set to continuation token to pass on a subsequent ListBuckets to resume the listing. |
StartAfter | This is the start-after value that was passed in on the request. | |
KeyCount | The number of buckets returned. | |
ContinuationToken | The continuation token that was supplied in the request. | |
MaxKeys | The max keys that were specified in the request. |