Each File stored on Amazon S3 (Object) is associated with a key, and metadata.
Metadata or Headers
is a set of Key - Value pairs. Metadata provides some basic and important details about the file.
Amazon S3 allows you to set the Metadata on S3 Objects at the time of uploading the Objects. S3 does not allow you to modify the Objects Metadata after uploading the Objects. To modify the Metadata for existing S3 Objects, the only way is to make a copy of the Object and set the Metadata. If you are a software programmer, you can use PUT Object - Copy S3 API in your software program to do this
and set metadata with the request using same Object Key.
You can update the Metadata of Amazon S3 Objects using Bucket Explorer User Interface very easily, using point and click, if you are not a software programmer. Bucket Explorer internally can make copy of Objects for you and you do not need to worry about doing all that work and writing any software program for that.
There are two types of metadata for files on S3.
1. System metadata
: System metadata is used and processed by Amazon S3.
2. User metadata
: User metadata or custom header is specified by you. Amazon S3 simply stores it and passes it back to you when you ask for it.
You can also change the
of an object while updating metadata.
Metadata size is limited to 2k bytes for the total length of all values and keys.