Definition
The logon message authenticates a user establishing a connection to a remote system. The logon message must be the first message sent by the application requesting to initiate a FIX session.
Message structure 66 distinct fields
Source order, including nested components and groups. Group counts precede the repeated entries. “Required here” is relative to the enclosing component or group, not unconditional in the message. A dash means not marked required; conditional requirements remain in the source notes. This is a reference, not a counterparty-specific validator.
StandardHeaderComponentRequired
MsgType = A
StandardHeader definition & usage →
FIXT.1.1 (Always unencrypted, must be first field in message)
(Always unencrypted, must be second field in message)
(Always unencrypted, must be third field in message)
Indicates application version using a service pack identifier. The ApplVerID applies to a specific message occurrence.
Used to support bilaterally agreed custom functionality
(Always unencrypted)
(Always unencrypted)
Trading partner company ID used when sending messages via a third party (Can be embedded within encrypted data section.)
Trading partner company ID used when sending messages via a third party (Can be embedded within encrypted data section.)
Required to identify length of encrypted section of message. (Always unencrypted)
Required when message body is encrypted. Always immediately follows SecureDataLen field.
(Can be embedded within encrypted data section.)
(Can be embedded within encrypted data section.)
Sender's LocationID (i.e. geographic location and/or desk) (Can be embedded within encrypted data section.)
"ADMIN" reserved for administrative messages not intended for a specific user. (Can be embedded within encrypted data section.)
Trading partner LocationID (i.e. geographic location and/or desk) (Can be embedded within encrypted data section.)
Trading partner SubID used when delivering messages via a third party. (Can be embedded within encrypted data section.)
Trading partner LocationID (i.e. geographic location and/or desk) used when delivering messages via a third party. (Can be embedded within encrypted data section.)
Trading partner SubID used when delivering messages via a third party. (Can be embedded within encrypted data section.)
Trading partner LocationID (i.e. geographic location and/or desk) used when delivering messages via a third party. (Can be embedded within encrypted data section.)
Always required for retransmitted messages, whether prompted by the sending system or as the result of a resend request. (Can be embedded within encrypted data section.)
Required when message may be duplicate of another message sent under a different sequence number. (Can be embedded within encrypted data section.)
(Can be embedded within encrypted data section.)
Required for message resent as a result of a ResendRequest. If data is not available set to same value as SendingTime (Can be embedded within encrypted data section.)
Required when specifying XmlData to identify the length of a XmlData message block. (Can be embedded within encrypted data section.)
Can contain a XML formatted message block (e.g. FIXML). Always immediately follows XmlDataLen field. (Can be embedded within encrypted data section.) See Volume 1: FIXML Support
Type of message encoding (non-ASCII characters) used in a message's "Encoded" fields. Required if any "Encoding" fields are used.
The last MsgSeqNum value received by the FIX engine and processed by downstream application, such as trading system or order routing system. Can be specified on every message sent. Useful for detecting a backlog with a counterparty.
HopGrpRepeating groupCount tag 627—
Number of repeating groups of historical "hop" information. Only applicable if OnBehalfOfCompID is used, however, its use is optional. Note that some market regulations or counterparties may require tracking of message hops.
(Always unencrypted)
Note same value used by both sides
Required for some authentication methods
Required for some authentication methods
Indicates both sides of a FIX session should reset sequence numbers
Optional, alternative via counterparty bi-lateral agreement message gap detection and recovery approach (see "Logon Message NextExpectedMsgSeqNum Processing" section)
Can be used to specify the maximum number of bytes supported for messages received
MsgTypeGrpRepeating groupCount tag 384—
MsgTypeGrp definition & usage →
Specifies the number of repeating RefMsgTypes specified
Specifies a specific, supported MsgType. Required if NoMsgTypes is > 0. Should be specified from the point of view of the sender of the Logon message
Indicates direction (send vs. receive) of a supported MsgType. Required if NoMsgTypes is > 0. Should be specified from the point of view of the sender of the Logon message
Specifies the service pack release being applied to an application message.
Specified the extension pack being applied to a message.
Specifies a custom extension to a message being applied at the session level.
Indicates that this Application Version (RefApplVerID(1130), RefApplExtID(1406),RefCstmApplVerID(1131)) is the default for the RefMsgType(372) field.
Can be used to specify that this FIX session will be sending and receiving "test" vs. "production" messages.
Note: minimal security exists without transport-level encryption.
Specifies a new password for the FIX Logon. The new password is used for subsequent logons.
Encrypted new password- encrypted via the method specified in the field EncryptedPasswordMethod(1400)
Session status at time of logon. Field is intended to be used when the logon is sent as an acknowledgement from acceptor of the FIX session.
The default version of FIX messages used in this session.
The default extension pack for FIX messages used in this session
The default custom application version (dictionary) for FIX messages used in this session
Available to provide a response to logon when used as a logon acknowledgement from acceptor back to the logon initiator.
Must be set if EncodedText field is specified and must immediately precede it.
Encoded (non-ASCII characters) representation of the Text field in the encoded format specified via the MessageEncoding field.
StandardTrailerComponentRequired
StandardTrailer definition & usage →
Required when trailer contains signature. Note: Not to be included within SecureData field
Note: Not to be included within SecureData field
(Always unencrypted, always last field in message)