Notational Convention (Sizes & Types)

This document covers the standard sizes and data types that this site references across other documents and packets.

Data types

Arrays of fields generally are only used when another field in the packet specifies how many entries there are or if the definition specifies a fixed size. The lack of a specified size in the definition indicates that the size is variable/non-fixed or unknown.

All numeric Battle.net types are little-endian. Battle.net uses the following types:

• STRING - A null-terminated array of characters. The encoding varies from packet to packet, but generally will either be ISO 8859-1 or less commonly UTF-8.
• STRINGLIST - A series of STRING values. This is like an array of STRING values in every way, except it is always variable/non-fixed size and terminated by an empty item at the end of the array (or otherwise double null-terminated).
• UINT8 - 8 bit (1 byte) unsigned integer, also known as u8 in C.
• UINT16 - 16 bit (2 byte) unsigned integer, also known as u16 in C.
• UINT32 - 32 bit (4 byte) unsigned integer, also known as u32 in C.
• UINT64 - 64 bit (8 byte) unsigned integer, also known as u64 in C.
• BOOL or BOOLEAN - An unsigned 8 bit or 32 bit (depending on packet) integer whose value is always 0 (FALSE) or 1 (TRUE).
• VOID - Data marked as VOID has no particular type or length. Where data is marked as VOID, additional information is given on its use.
• FILETIME - A Windows struct, used to store filetime information. It can be read as a UINT64 or two UINT32s.

If the field is defined with square brackets, then this is an array of that type. For example, UINT32[] is an array of UINT32 values. The number of array elements should be specified in the format, or if not, is specified by the value of another field, often preceeding the variable-length array of fields.

"UINT32" strings

Some data which may at first appear to be strings are in fact UINT32s; product & platform identification codes, for example. Since all data is little-endian, on little-endian systems this can be specified by the platform-dependant 'ABCD' code in C, for instance. On the wire, the value appears in reverse of what is written/should be interpreted due to the endian.

Examples of "UINT32" string values seen throughout Battle.net's protocol:

Packet	Field	Example value(s)
C>S 0x50 SID_AUTH_INFO	Platform	IX86
C>S 0x50 SID_AUTH_INFO	Product	SEXP
C>S 0x50 SID_AUTH_INFO	Language	enUS
all clan packets	Clan Tag	ABC\x00
S>C 0x05 PKT_SERVERPING	UDP Code	bnet
S>C 0x44 SID_WARCRAFTGENERAL	Ladder Type	SOLO

Common fields

Sizes and information of other fields commonly seen on Battle.net.

Item	Max. Length (bytes)	Notes
Account name	15	When creating an account, names longer than 15 bytes are truncated by the server.
Character name	15
Username	64	(a.k.a. online name) This string is a concatenation set by the server that follows the format: Character#Realm*w#Account#Serial#Realm. Note that prior to 2018, the format was: Character@Realm*w#Account#Serial@Realm The w# part of the string is normally not present, but can be seen in invisible fields when using WarCraft III accounts, such as the username field of an EID_INFO chat event. The Character#Realm* part of the string is present only when the client is connected as Diablo II or its expansion. In addition, Character#Realm is present only if the user is on a closed realm character, and is missing if using an open realm character; open realm usernames appear as *Account#Serial#Realm. The #Serial part of the string is added only when the account is logged on multiple times and needs a unique online name, it begins at 2 and is incremented until a number is available that is unique. Official Blizzard clients assign a 64-character variable for usernames, so the use of a variable of at least that length is advisable for future compatibility.
Channel name	31	Any channel name whose length exceeds this value is truncated.
CD-Key owner	15	Any key owner whose length exceeds this value is truncated.
Statstring	128	A series of mostly numeric values usually separated by a single space character.
Chat text	224	This is the maximum for game clients. Chat clients can receive up to 255 bytes of chat text. This includes the null terminator. Longer text is truncated.