Amazon S3 server access log format - Amazon Simple Storage Service
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Amazon S3 server access log format

Server access logging provides detailed records for the requests that are made to an Amazon S3 bucket. You can use server access logs for the following purposes:

  • Performing security and access audits

  • Learning about your customer base

  • Understanding your Amazon S3 bill

This section describes the format and other details about Amazon S3 server access log files.

Server access log files consist of a sequence of newline-delimited log records. Each log record represents one request and consists of space-delimited fields.

The following is an example log consisting of five log records.

79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be DOC-EXAMPLE-BUCKET1 [06/Feb/2019:00:00:38 +0000] 192.0.2.3 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be 3E57427F3EXAMPLE REST.GET.VERSIONING - "GET /DOC-EXAMPLE-BUCKET1?versioning HTTP/1.1" 200 - 113 - 7 - "-" "S3Console/0.4" - s9lzHYrFp76ZVxRcpX9+5cjAnEH2ROuNkd2BHfIa6UkFVdtjf5mKR3/eTPFvsiP/XV/VLi31234= SigV4 ECDHE-RSA-AES128-GCM-SHA256 AuthHeader DOC-EXAMPLE-BUCKET1.s3.us-west-1.amazonaws.com.cn TLSV1.2 arn:aws-cn:s3:us-west-1:123456789012:accesspoint/example-AP Yes 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be DOC-EXAMPLE-BUCKET1 [06/Feb/2019:00:00:38 +0000] 192.0.2.3 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be 891CE47D2EXAMPLE REST.GET.LOGGING_STATUS - "GET /DOC-EXAMPLE-BUCKET1?logging HTTP/1.1" 200 - 242 - 11 - "-" "S3Console/0.4" - 9vKBE6vMhrNiWHZmb2L0mXOcqPGzQOI5XLnCtZNPxev+Hf+7tpT6sxDwDty4LHBUOZJG96N1234= SigV4 ECDHE-RSA-AES128-GCM-SHA256 AuthHeader DOC-EXAMPLE-BUCKET1.s3.us-west-1.amazonaws.com.cn TLSV1.2 - - 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be DOC-EXAMPLE-BUCKET1 [06/Feb/2019:00:00:38 +0000] 192.0.2.3 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be A1206F460EXAMPLE REST.GET.BUCKETPOLICY - "GET /DOC-EXAMPLE-BUCKET1?policy HTTP/1.1" 404 NoSuchBucketPolicy 297 - 38 - "-" "S3Console/0.4" - BNaBsXZQQDbssi6xMBdBU2sLt+Yf5kZDmeBUP35sFoKa3sLLeMC78iwEIWxs99CRUrbS4n11234= SigV4 ECDHE-RSA-AES128-GCM-SHA256 AuthHeader DOC-EXAMPLE-BUCKET1.s3.us-west-1.amazonaws.com.cn TLSV1.2 - Yes 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be DOC-EXAMPLE-BUCKET1 [06/Feb/2019:00:01:00 +0000] 192.0.2.3 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be 7B4A0FABBEXAMPLE REST.GET.VERSIONING - "GET /DOC-EXAMPLE-BUCKET1?versioning HTTP/1.1" 200 - 113 - 33 - "-" "S3Console/0.4" - Ke1bUcazaN1jWuUlPJaxF64cQVpUEhoZKEG/hmy/gijN/I1DeWqDfFvnpybfEseEME/u7ME1234= SigV4 ECDHE-RSA-AES128-GCM-SHA256 AuthHeader DOC-EXAMPLE-BUCKET1.s3.us-west-1.amazonaws.com.cn TLSV1.2 - - 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be DOC-EXAMPLE-BUCKET1 [06/Feb/2019:00:01:57 +0000] 192.0.2.3 79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be DD6CC733AEXAMPLE REST.PUT.OBJECT s3-dg.pdf "PUT /DOC-EXAMPLE-BUCKET1/s3-dg.pdf HTTP/1.1" 200 - - 4406583 41754 28 "-" "S3Console/0.4" - 10S62Zv81kBW7BB6SX4XJ48o6kpcl6LPwEoizZQQxJd5qDSCTLX0TgS37kYUBKQW3+bPdrg1234= SigV4 ECDHE-RSA-AES128-SHA AuthHeader DOC-EXAMPLE-BUCKET1.s3.us-west-1.amazonaws.com.cn TLSV1.2 - Yes
Note

Any field can be set to - to indicate that the data was unknown or unavailable, or that the field was not applicable to this request.

Important

During the next few weeks, we are adding a new field, aclRequired, to Amazon S3 server access logs and Amazon CloudTrail logs. This field will indicate if your Amazon S3 requests required an access control list (ACL) for authorization. You can use this information to migrate those ACL permissions to the appropriate bucket policies and disable ACLs. This process is currently occurring across all Amazon Web Services Regions, including the Amazon GovCloud (US) Regions and the Amazon China Regions. If you don't see the aclRequired field, the rollout hasn't been completed in your Region.

Log record fields

The following list describes the log record fields.

Bucket Owner

The canonical user ID of the owner of the source bucket. The canonical user ID is another form of the Amazon Web Services account ID. For more information about the canonical user ID, see Amazon Web Services account identifiers in the Amazon General Reference. For information about how to find the canonical user ID for your account, see Finding the canonical user ID for your Amazon Web Services account.

Example entry

79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be
Bucket

The name of the bucket that the request was processed against. If the system receives a malformed request and cannot determine the bucket, the request will not appear in any server access log.

Example entry

DOC-EXAMPLE-BUCKET1
Time

The time at which the request was received; these dates and times are in Coordinated Universal Time (UTC). The format, using strftime() terminology, is as follows: [%d/%b/%Y:%H:%M:%S %z]

Example entry

[06/Feb/2019:00:00:38 +0000]
Remote IP

The apparent IP address of the requester. Intermediate proxies and firewalls might obscure the actual IP address of the machine that's making the request.

Example entry

192.0.2.3
Requester

The canonical user ID of the requester, or a - for unauthenticated requests. If the requester was an Amazon Identity and Access Management (IAM) user, this field returns the requester's IAM user name along with the Amazon root account that the IAM user belongs to. This identifier is the same one used for access control purposes.

Example entry

79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be
Request ID

A string generated by Amazon S3 to uniquely identify each request.

Example entry

3E57427F33A59F07
Operation

The operation listed here is declared as SOAP.operation, REST.HTTP_method.resource_type, WEBSITE.HTTP_method.resource_type, or BATCH.DELETE.OBJECT, or S3.action.resource_type for Lifecycle and logging.

Example entry

REST.PUT.OBJECT
Key

The key (object name) part of the request, URL encoded, or - if the operation does not take a key parameter.

Example entry

/photos/2019/08/puppy.jpg
Request-URI

The Request-URI part of the HTTP request message.

Example Entry

"GET /DOC-EXAMPLE-BUCKET1/photos/2019/08/puppy.jpg?x-foo=bar HTTP/1.1"
HTTP status

The numeric HTTP status code of the response.

Example entry

200
Error Code

The Amazon S3 Error code, or - if no error occurred.

Example entry

NoSuchBucket
Bytes Sent

The number of response bytes sent, excluding HTTP protocol overhead, or - if zero.

Example entry

2662992
Object Size

The total size of the object in question.

Example entry

3462992
Total Time

The number of milliseconds that the request was in flight from the server's perspective. This value is measured from the time that your request is received to the time that the last byte of the response is sent. Measurements made from the client's perspective might be longer because of network latency.

Example entry

70
Turn-Around Time

The number of milliseconds that Amazon S3 spent processing your request. This value is measured from the time that the last byte of your request was received until the time that the first byte of the response was sent.

Example entry

10
Referer

The value of the HTTP Referer header, if present. HTTP user-agents (for example, browsers) typically set this header to the URL of the linking or embedding page when making a request.

Example entry

"http://www.example.com/webservices"
User-Agent

The value of the HTTP User-Agent header.

Example entry

"curl/7.15.1"
Version Id

The version ID in the request, or - if the operation doesn't take a versionId parameter.

Example entry

3HL4kqtJvjVBH40Nrjfkd
Host Id

The x-amz-id-2 or Amazon S3 extended request ID.

Example entry

s9lzHYrFp76ZVxRcpX9+5cjAnEH2ROuNkd2BHfIa6UkFVdtjf5mKR3/eTPFvsiP/XV/VLi31234=
Signature Version

The signature version, SigV2 or SigV4, that was used to authenticate the request or a - for unauthenticated requests.

Example entry

SigV2
Cipher Suite

The Secure Sockets Layer (SSL) cipher that was negotiated for an HTTPS request or a - for HTTP.

Example entry

ECDHE-RSA-AES128-GCM-SHA256
Authentication Type

The type of request authentication used: AuthHeader for authentication headers, QueryString for query string (presigned URL), or a - for unauthenticated requests.

Example entry

AuthHeader
Host Header

The endpoint used to connect to Amazon S3.

Example entry

s3.us-west-2.amazonaws.com.cn

Some earlier Regions support legacy endpoints. You might see these endpoints in your server access logs or Amazon CloudTrail logs. For more information, see Legacy endpoints. For a complete list of Amazon S3 Regions and endpoints, see Amazon S3 endpoints and quotas in the Amazon Web Services General Reference.

TLS version

The Transport Layer Security (TLS) version negotiated by the client. The value is one of following: TLSv1, TLSv1.1, TLSv1.2, or - if TLS wasn't used.

Example entry

TLSv1.2
Access Point ARN

The Amazon Resource Name (ARN) of the access point of the request. If the access point ARN is malformed or not used, the field will contain a -. For more information about access points, see Using access points. For more information about ARNs, see Amazon Resource Name (ARN) in the Amazon Reference Guide.

Example entry

arn:aws-cn:s3:us-east-1:123456789012:accesspoint/example-AP
aclRequired

A string that indicates whether the request required an access control list (ACL) for authorization. If the request required an ACL for authorization, the string is Yes. If no ACLs were required, the string is -. For more information about ACLs, see Access control list (ACL) overview. For more information about using the aclRequired field to disable ACLs, see Controlling ownership of objects and disabling ACLs for your bucket.

Example entry

Yes
Important

During the next few weeks, we are adding a new field, aclRequired, to Amazon S3 server access logs and Amazon CloudTrail logs. This field will indicate if your Amazon S3 requests required an access control list (ACL) for authorization. You can use this information to migrate those ACL permissions to the appropriate bucket policies and disable ACLs. This process is currently occurring across all Amazon Web Services Regions, including the Amazon GovCloud (US) Regions and the Amazon China Regions. If you don't see the aclRequired field, the rollout hasn't been completed in your Region.

Additional logging for copy operations

A copy operation involves a GET and a PUT. For that reason, we log two records when performing a copy operation. The previous section describes the fields related to the PUT part of the operation. The following list describes the fields in the record that relate to the GET part of the copy operation.

Bucket Owner

The canonical user ID of the bucket that stores the object being copied. The canonical user ID is another form of the Amazon Web Services account ID. For more information about the canonical user ID, see Amazon Web Services account identifiers in the Amazon General Reference. For information about how to find the canonical user ID for your account, see Finding the canonical user ID for your Amazon Web Services account.

Example entry

79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be
Bucket

The name of the bucket that stores the object that's being copied.

Example entry

DOC-EXAMPLE-BUCKET1
Time

The time at which the request was received; these dates and times are in Coordinated Universal Time (UTC). The format, using strftime() terminology, is as follows: [%d/%B/%Y:%H:%M:%S %z]

Example entry

[06/Feb/2019:00:00:38 +0000]
Remote IP

The apparent IP address of the requester. Intermediate proxies and firewalls might obscure the actual IP address of the machine that's making the request.

Example entry

192.0.2.3
Requester

The canonical user ID of the requester, or a - for unauthenticated requests. If the requester was an IAM user, this field will return the requester's IAM user name along with the Amazon root account that the IAM user belongs to. This identifier is the same one used for access control purposes.

Example entry

79a59df900b949e55d96a1e698fbacedfd6e09d98eacf8f8d5218e7cd47ef2be
Request ID

A string generated by Amazon S3 to uniquely identify each request.

Example entry

3E57427F33A59F07
Operation

The operation listed here is declared as SOAP.operation, REST.HTTP_method.resource_type, WEBSITE.HTTP_method.resource_type, or BATCH.DELETE.OBJECT.

Example entry

REST.COPY.OBJECT_GET
Key

The key (object name) of the object being copied, or - if the operation doesn't take a key parameter.

Example entry

/photos/2019/08/puppy.jpg
Request-URI

The Request-URI part of the HTTP request message.

Example entry

"GET /DOC-EXAMPLE-BUCKET1/photos/2019/08/puppy.jpg?x-foo=bar"
HTTP status

The numeric HTTP status code of the GET portion of the copy operation.

Example entry

200
Error Code

The Amazon S3 Error code of the GET portion of the copy operation, or - if no error occurred.

Example entry

NoSuchBucket
Bytes Sent

The number of response bytes sent, excluding the HTTP protocol overhead, or - if zero.

Example entry

2662992
Object Size

The total size of the object in question.

Example entry

3462992
Total Time

The number of milliseconds that the request was in flight from the server's perspective. This value is measured from the time that your request is received to the time that the last byte of the response is sent. Measurements made from the client's perspective might be longer because of network latency.

Example entry

70
Turn-Around Time

The number of milliseconds that Amazon S3 spent processing your request. This value is measured from the time that the last byte of your request was received until the time that the first byte of the response was sent.

Example entry

10
Referer

The value of the HTTP Referer header, if present. HTTP user-agents (for example, browsers) typically set this header to the URL of the linking or embedding page when making a request.

Example entry

"http://www.example.com/webservices"
User-Agent

The value of the HTTP User-Agent header.

Example entry

"curl/7.15.1"
Version Id

The version ID of the object being copied, or - if the x-amz-copy-source header didn't specify a versionId parameter as part of the copy source.

Example Entry

3HL4kqtJvjVBH40Nrjfkd
Host Id

The x-amz-id-2 or Amazon S3 extended request ID.

Example entry

s9lzHYrFp76ZVxRcpX9+5cjAnEH2ROuNkd2BHfIa6UkFVdtjf5mKR3/eTPFvsiP/XV/VLi31234=
Signature Version

The signature version, SigV2 or SigV4, that was used to authenticate the request, or a - for unauthenticated requests.

Example entry

SigV4
Cipher Suite

The Secure Sockets Layer (SSL) cipher that was negotiated for an HTTPS request, or a - for HTTP.

Example entry

ECDHE-RSA-AES128-GCM-SHA256
Authentication Type

The type of request authentication used: AuthHeader for authentication headers, QueryString for query strings (presigned URLs), or a - for unauthenticated requests.

Example entry

AuthHeader
Host Header

The endpoint that was used to connect to Amazon S3.

Example entry

s3.us-west-2.amazonaws.com.cn

Some earlier Regions support legacy endpoints. You might see these endpoints in your server access logs or Amazon CloudTrail logs. For more information, see Legacy endpoints. For a complete list of Amazon S3 Regions and endpoints, see Amazon S3 endpoints and quotas in the Amazon Web Services General Reference.

TLS version

The Transport Layer Security (TLS) version negotiated by the client. The value is one of following: TLSv1, TLSv1.1, TLSv1.2, or - if TLS wasn't used.

Example entry

TLSv1.2
Access Point ARN

The Amazon Resource Name (ARN) of the access point of the request. If the access point ARN is malformed or not used, the field will contain a -. For more information about access points, see Using access points. For more information about ARNs, see Amazon Resource Name (ARN) in the Amazon Reference Guide.

Example entry

arn:aws-cn:s3:us-east-1:123456789012:accesspoint/example-AP
aclRequired

A string that indicates whether the request required an access control list (ACL) for authorization. If the request required an ACL for authorization, the string is Yes. If no ACLs were required, the string is -. For more information about ACLs, see Access control list (ACL) overview. For more information about using the aclRequired field to disable ACLs, see Controlling ownership of objects and disabling ACLs for your bucket.

Example entry

Yes
Important

During the next few weeks, we are adding a new field, aclRequired, to Amazon S3 server access logs and Amazon CloudTrail logs. This field will indicate if your Amazon S3 requests required an access control list (ACL) for authorization. You can use this information to migrate those ACL permissions to the appropriate bucket policies and disable ACLs. This process is currently occurring across all Amazon Web Services Regions, including the Amazon GovCloud (US) Regions and the Amazon China Regions. If you don't see the aclRequired field, the rollout hasn't been completed in your Region.

Custom access log information

You can include custom information to be stored in the access log record for a request. To do this, add a custom query-string parameter to the URL for the request. Amazon S3 ignores query-string parameters that begin with x-, but includes those parameters in the access log record for the request, as part of the Request-URI field of the log record.

For example, a GET request for "s3.amazonaws.com/DOC-EXAMPLE-BUCKET1/photos/2019/08/puppy.jpg?x-user=johndoe" works the same as the request for "s3.amazonaws.com/DOC-EXAMPLE-BUCKET1/photos/2019/08/puppy.jpg", except that the "x-user=johndoe" string is included in the Request-URI field for the associated log record. This functionality is available in the REST interface only.

Programming considerations for extensible server access log format

Occasionally, we might extend the access log record format by adding new fields to the end of each line. Therefore, make sure that any of your code that parses server access logs can handle trailing fields that it might not understand.