Variables and Expressions

Table of Contents

Variables

Variable types: AutoHotkey has no explicitly defined variable types. Instead, any variable can contain a string, integer, floating-point number, or reference to an object. Additionally, numbers are automatically converted to or from strings as required. The Type function can be used to determine the actual type of a value.

Variable scope and declarations: With the exception of local variables in functions, all variables are global; that is, their contents may be read or altered by any part of the script. Except where noted on the functions page, variables do not need to be declared; they come into existence simply by using them (and each variable starts off empty/blank).

Variable names: Variable names are not case sensitive (for example, CurrentDate is the same as currentdate). Variable names may be up to 253 characters long and may consist of letters, numbers, underscore and non-ASCII characters. Variable names must not start with a digit.

Reserved words: and, contains, in, is, new, not and or. These words are reserved for use as operators and therefore cannot be used as variable names when written literally in an expression.

Names of control flow statements are also reserved, primarily to detect mistakes. This includes: Break, Catch, Continue, Else, Finally, For, Gosub, Goto, If, Loop, LoopFile, LoopParse, LoopRead, LoopReg, Return, Throw, Try, Until, While

Functions, classes and window groups use the same validation as variables and therefore have the same restrictions.

Storing values in variables: To store a string or number in a variable, use the colon-equal operator (:=) followed by a number, quoted string or any other type of expression. For example:

MyNumber := 123
MyString := "This is a literal string."
CopyOfVar := Var

Variables which have not been assigned a value contain an empty string by default. Therefore, to erase the contents of a variable, simply assign an empty string:

MyVar := ""

A variable can also be assigned a value indirectly, by using it as an output variable of a command. For example:

WinGetTitle Title, A

Retrieving the contents of variables: To include the contents of a variable in a string, enclose the variable name in percent signs. For example:

MsgBox, The value in the variable named Var is %Var%.
MsgBox("The value in the variable named Var is %Var%.")

By contrast, the percent signs are omitted for variable references in an expression (other than in a quoted string). For example:

MsgBox("The sum of X and Y is " . (X + Y))  ; A period is used to concatenate (join) two strings.

Comparing variables: Please read the expressions section below for important notes about the different kinds of comparisons.

Expressions

Expressions are used to perform one or more operations upon a series of variables, literal strings, and/or literal numbers.

Variable names in an expression are not enclosed in percent signs (except for variables inside quoted strings, and pseudo-arrays and other double references). Consequently, literal strings must be enclosed in double quotes to distinguish them from variables. For example:

if (CurrentSetting > 100 or FoundColor <> "Blue")
    MsgBox The setting is too high or the wrong color is present.

In the example above, "Blue" appears in quotes because it is a literal string. Single-quote marks (') and double-quote marks (") function identically, except that a string enclosed in single-quote marks can contain literal double-quote marks and vice versa. Therefore, to include an actual quote mark inside a literal string, escape the quote mark or enclose the string in the opposite type of quote mark. For example:

MsgBox % "She said, `"An apple a day.`""
MsgBox % 'She said, "An apple a day."'

Empty strings: To specify an empty string in an expression, use an empty pair of quotes. For example, the statement if (MyVar <> "") would be true if MyVar is not blank.

Storing the result of an expression: To assign a result to a variable, use the := operator. For example:

NetPrice := Price * (1 - Discount/100)

Boolean values: When an expression is required to evaluate to true or false (such as an IF-statement), a blank or zero result is considered false and all other results are considered true. For example, the statement if ItemCount would be false only if ItemCount is blank or 0. Similarly, the expression if not ItemCount would yield the opposite result.

Operators such as NOT/>/=/< automatically produce a true or false value: they yield 1 for true and 0 for false. However, the AND/OR operators always produce one of the input values. For example, in the following expression, the variable Done is assigned 1 if A_Index is greater than 5 or the value of FoundIt in all other cases:

Done := A_Index > 5 or FoundIt

As hinted above, a variable can be used to hold a false value simply by making it blank or assigning 0 to it. To take advantage of this, the shorthand statement if Done can be used to check whether the variable Done is true or false.

In an expression, the keywords true and false resolve to 1 and 0. They can be used to make a script more readable as in these examples:

CaseSensitive := false
ContinueSearch := true

Integers and floating point: Within an expression, numbers are considered to be floating point if they contain a decimal point or scientific notation; otherwise, they are integers. For most operators -- such as addition and multiplication -- if either of the inputs is a floating point number, the result will also be a floating point number.

Within expressions and non-expressions alike, integers may be written in either hexadecimal or decimal format. Hexadecimal numbers all start with the prefix 0x. For example, Sleep 0xFF is equivalent to Sleep 255. Floating point numbers can optionally be written in scientific notation, with or without a decimal point (e.g. 1e4 or -2.1E-4).

Within expressions, unquoted literal numbers such as 128, 0x7F and 1.0 are converted to pure numbers before the script begins executing, so converting the number to a string may produce a value different to the original literal value. For example:

MsgBox(0x7F)  ; Shows 128
MsgBox(1.00)  ; Shows 1.0

Force an expression: An expression can be used in a parameter that does not directly support it (except an OutputVar parameter) by preceding the expression with a percent sign and a space or tab. For example:

FileAppend, % MyArray[i], My File.txt
MsgBox % "The variable MyVar contains " . MyVar . "."
WinSetTransparent, % X + 100
Control, Choose, % CurrentSelection - 1

An expression can also be inserted at any point in a string by enclosing it in percent signs, as in the following example:

MsgBox, The time is %FormatTime(A_Now, "Time")%.

OutputVar parameters also allow this, but the result of the expression should be the (full or partial) name of a variable, as a string.

Operators in Expressions

Operators of equal precedence such as multiply (*) and divide (/) are evaluated in left-to-right order unless otherwise specified below. By contrast, an operator of lower precedence such as add (+) is evaluated after a higher one such as multiply (*). For example, 3 + 2 * 2 is evaluated as 3 + (2 * 2). Parentheses may be used to override precedence as in this example: (3 + 2) * 2

Except where noted below, any blank value (empty string) or non-numeric value involved in a math operation is not assumed to be zero. Instead, it is treated as an error, which causes that part of the expression to evaluate to an empty string. For example, if the variable X is blank, the expression X+1 yields a blank value rather than 1.

Expression Operators (in descending precedence order)

%Expr%

Embeds an expression (Expr) within a quoted string, or dynamically retrieves a variable by name. Percent signs cannot be used directly within Expr due to ambiguity, but can be nested within quoted strings and parentheses. Otherwise, Expr can be any expression.

Within a quoted string: Evaluates Expr and inserts the result at that position within the string. For example, the following are equivalent:

MsgBox("Hello, %A_UserName%!")
MsgBox, Hello`, %A_Username%!
MsgBox("Hello, " A_UserName "!")

Elsewhere: Dynamically retrieves a variable by name. The result of the sub-expression must be the name or partial name of the variable to be retrieved. If there are any adjoining %Expr% sequences and partial variable names (without any spaces or other characters between them), they are combined to form a single name.

If the variable does not already exist, a blank variable is created. An exception is thrown if the name is invalid.

This is most commonly used to reference pseudo-array elements such as in the following example:

Loop 4
    MsgBox("IP address " A_Index " is " A_IPAddress%A_Index%)

Although this is historically known as a "double-deref", this term is inaccurate when Expr does not contain a variable (first deref), and also when the resulting variable is the target of an assignment, not being dereferenced (second deref).

x.y Object access. Get or set a value or call a method of object x, where y is a literal value. See object syntax.
new new Class or new Class(Params) creates a new object derived from Class. For example, x := new y is often equivalent to x := {base: y}. Class can be almost any expression which produces a class object, but is typically a class name such as GlobalClass or GlobalClass.NestedClass. More complex cases such as new new (getClass())(params1)(params2) are also supported, but there must be no space between the class expression and parameter list. For details, see Custom Objects.
++
--

Pre- and post-increment/decrement. Adds or subtracts 1 from a variable. The operator may appear either before or after the variable's name. If it appears before the name, the operation is performed immediately and its result is used by the next operation. For example, Var := ++X increments X immediately and then assigns its value to Var. Conversely, if the operator appears after the variable's name, the operation is performed after the variable is used by the next operation. For example, Var := X++ increments X only after assigning the current value of X to Var. Due to backward compatibility, the operators ++ and -- treat blank variables as zero, but only when they are alone on a line; for example, y:=1, ++x and MsgBox % ++x both produce a blank result when x is blank.

If the target variable is empty, the operators ++ and -- treat it as zero. This allows a line such as Var++ to be used in a hotkey without Var having been initialized in the auto-execute section.

** Power. Both the base and the exponent may contain a decimal point. If the exponent is negative, the result will be formatted as a floating point number even if the base and exponent are both integers. Since ** is of higher precedence than unary minus, -2**2 is evaluated like -(2**2) and so yields -4. Thus, to raise a literal negative number to a power, enclose it in parentheses such as (-2)**2. Note: A negative base combined with a fractional exponent such as (-2)**0.5 is not supported; it will yield an empty string. But both (-2)**2 and (-2)**2.0 are supported.
-
!
~
& *

Unary minus (-): Inverts the sign of its operand.

Unary plus (+): +N is equivalent to -(-N). This has no effect when applied to a pure number, but can be used to convert numeric strings to pure numbers. As with other math operators, the result is a blank value (empty string) if the operand is not a number or numeric string.

Logical-not (!): If the operand is blank or 0, the result of applying logical-not is 1, which means "true". Otherwise, the result is 0 (false). For example: !x or !(y and z). Note: The word NOT is synonymous with ! except that ! has a higher precedence. Consecutive unary operators such as !!Var are allowed because they are evaluated in right-to-left order.

Bitwise-not (~): This inverts each bit of its operand. If the operand is a floating point value, it is truncated to an integer prior to the calculation. If the operand is between 0 and 4294967295 (0xffffffff), it will be treated as an unsigned 32-bit value. Otherwise, it is treated as a signed 64-bit value. For example, ~0xf0f evaluates to 0xfffff0f0 (4294963440).

Address (&): &MyVar retrieves the address of MyVar's contents in memory, which is typically used with DllCall structures. MyVar's contents can be a string, a 64-bit integer, a 64-bit floating-point number, or an object.

Dereference (*): *Expression assumes that Expression resolves to a numeric memory address; it retrieves the byte at that address as a number between 0 and 255 (0 is always retrieved if the address is 0; but any other invalid address must be avoided because it might crash the script). However, NumGet() generally performs much better when retrieving binary numbers.

*
/
//

Multiply (*): The result is an integer if both inputs are integers; otherwise, it is a floating point number.

True divide (/): True division yields a floating point result even when both inputs are integers. For example, 3/2 yields 1.5 rather than 1, and 4/2 yields 2.0 rather than 2.

Floor divide (//): The double-slash operator uses high-performance integer division if the two inputs are integers. For example, 5//3 is 1 and 5//-3 is -1. If either of the inputs is in floating point format, floating point division is performed and the result is truncated to the nearest integer to the left. For example, 5//3.0 is 1.0 and 5.0//-3 is -2.0. Although the result of this floating point division is an integer, it is stored in floating point format so that anything else that uses it will see it as such. For modulo, see mod().

The *= and /= operators are a shorthand way to multiply or divide the value in a variable by another value. For example, Var*=2 produces the same result as Var:=Var*2 (though the former performs better).

Division by zero yields a blank result (empty string).

+
-

Add (+) and subtract (-). On a related note, the += and -= operators are a shorthand way to increment or decrement a variable. For example, Var+=2 produces the same result as Var:=Var+2 (though the former performs better). Similarly, a variable can be increased or decreased by 1 by using Var++, Var--, ++Var, or --Var.

<<
>>
Bit shift left (<<) and right (>>). Example usage: Value1 << Value2. Any floating point input is truncated to an integer prior to the calculation. Shift left (<<) is equivalent to multiplying Value1 by "2 to the Value2th power". Shift right (>>) is equivalent to dividing Value1 by "2 to the Value2th power" and rounding the result to the nearest integer leftward on the number line; for example, -3>>1 is -2.
&
^
|
Bitwise-and (&), bitwise-exclusive-or (^), and bitwise-or (|). Of the three, & has the highest precedence and | has the lowest. Any floating point input is truncated to an integer prior to the calculation.
.

Concatenate. The period (dot) operator is used to combine two items into a single string (there must be at least one space on each side of the period). You may also omit the period to achieve the same result (except where ambiguous such as x -y, or when the item on the right side has a leading ++ or --). When the dot is omitted, there must be at least one space between the items to be merged.

Var := "The color is " . FoundColor  ; Explicit concat
Var := "The color is " FoundColor    ; Auto-concat
Var := "The color is %FoundColor%"   ; Variable substitution within a string

Sub-expressions can also be concatenated. For example: Var := "The net price is " . Price * (1 - Discount/100).

A line that begins with a period (or any other operator) is automatically appended to the line above it.

The entire length of each input is used, even if it includes binary zero. For example, Chr(0x2010) Chr(0x0000) Chr(0x4030) produces the following string of bytes (due to UTF-16-LE encoding): 0x10, 0x20, 0, 0, 0x30, 0x40. The result has an additional null-terminator (binary zero) which is not included in the length.

~= Shorthand for RegExMatch. For example, the result of "abc123" ~= "\d" is 4 (the position of the first numeric character).
>   <
>= <=

Greater (>), less (<), greater-or-equal (>=), and less-or-equal (<=). If either of the inputs is not numeric (or both are strings), they are compared alphabetically. For example, 2 < "10" is true whereas "2" < "10" is false. The comparison is case sensitive only if StringCaseSense has been turned on. See also: Sort

When comparing strings, these operators compare only up to the first binary zero.

=
==
<> !=

Equal (=), case-sensitive-equal (==), and not-equal (<> or !=). The operators != and <> are identical in function. The == operator behaves identically to = except when either of the inputs is not numeric (or both are strings), in which case == is always case sensitive and = is always case insensitive (the method of insensitivity depends on StringCaseSense). By contrast, <> and != obey StringCaseSense.

The == operator can be used to compare strings which contain binary zero. All other comparison operators except ~= compare only up to the first binary zero.

IS
IN
CONTAINS

Value is Type: Yields true (1) if value is of the given type or false (0) otherwise. For details, see Value is Type.

in and contains are reserved for future use.

NOT Logical-NOT. Except for its lower precedence, this is the same as the ! operator. For example, not (x = 3 or y = 3) is the same as !(x = 3 or y = 3).
AND
&&

Both of these are logical-AND. For example: x > 3 and x < 10.

In the expression x and y, if x is true, the result is y. Otherwise the result is x, and y is not evaluated at all - short-circuit evaluation is applied to enhance performance. Although the result is not limited to boolean 0 and 1, it can be interpreted as a boolean value as with any other expression. In effect, the result is true only if both inputs are true.

A line that begins with AND/OR/&&/|| (or any other operator) is automatically appended to the line above it.

OR
||

Both of these are logical-OR. For example: x <= 3 or x >= 10.

In the expression x or y, if x is false, the result is y. Otherwise the result is x, and y is not evaluated at all - short-circuit evaluation is applied to enhance performance. Although the result is not limited to boolean 0 and 1, it can be interpreted as a boolean value as with any other expression. In effect, the result is true if either input is true.

?:

Ternary operator. This operator is a shorthand replacement for the if-else statement. It evaluates the condition on its left side to determine which of its two branches should become its final result. For example, var := x>y ? 2 : 3 stores 2 in Var if x is greater than y; otherwise it stores 3. To enhance performance, only the winning branch is evaluated (see short-circuit evaluation).

:=
+=
-=
*=
/=
//=
.=
|=
&=
^=
>>=
<<=

Assign. Performs an operation on the contents of a variable and stores the result back in the same variable. The simplest assignment operator is colon-equals (:=), which stores the result of an expression in a variable. For a description of what the other operators do, see their related entries in this table. For example, Var //= 2 performs floor division to divide Var by 2, then stores the result back in Var. Similarly, Var .= "abc" is a shorthand way of writing Var := Var . "abc".

Unlike most other operators, assignments are evaluated from right to left. Consequently, a line such as Var1 := Var2 := 0 first assigns 0 to Var2 then assigns Var2 to Var1.

If an assignment is used as the input for some other operator, its value is the variable itself. For example, the expression (Var+=2) > 50 is true if the newly-increased value in Var is greater than 50. This also allows an assignment to be passed ByRef, or its address taken; for example: &(x:="abc").

The precedence of the assignment operators is automatically raised when it would avoid a syntax error or provide more intuitive behavior. For example: not x:=y is evaluated as not (x:=y). Similarly, ++Var := X is evaluated as ++(Var := X); and Z>0 ? X:=2 : Y:=2 is evaluated as Z>0 ? (X:=2) : (Y:=2).

If the target variable is empty, the operators += and -= treat it as zero. This allows a line such as Var += 1 to be used in a hotkey without Var having been initialized in the auto-execute section.

,

Comma (multi-statement). Commas may be used to write multiple sub-expressions on a single line. This is most commonly used to group together multiple assignments or function calls. For example: x:=1, y+=2, ++index, func(). Such statements are executed in order from left to right. Note: A line that begins with a comma (or any other operator) is automatically appended to the line above it. See also: comma performance.

When a multi-statement expression is used inside another expression, each sub-expression is evaluated and the value of the final (rightmost) sub-expression becomes the result of the expression. For example, x := (++y, 1) increments y and assigns the number 1 to x.

mod()
round()
abs()

These and other built-in math functions are described here.

%func%()

See Dynamically Calling a Function.
F(p*) See Variadic Functions.
x[y] Object access. Get or set a value or call a method of object x, where y is a parameter list or calculated method name. See array syntax and object syntax.

Performance: The comma operator is usually faster than writing separate expressions, especially when assigning one variable to another (e.g. x:=y, a:=b). Performance continues to improve as more and more expressions are combined into a single expression; for example, it may be 35% faster to combine five or ten simple expressions into a single expression.

Built-in Variables

The following variables are built into the program and can be referenced by any script. Except where noted, these variables are read-only; that is, their contents cannot be directly altered by the script.

Table of Contents

Special Characters

A_Space Contains a single space character.
A_Tab Contains a single tab character.

Script Properties

A_Args Read/write: Contains an array of command line parameters. For details, see Passing Command Line Parameters to a Script.
A_WorkingDir

Read/write: The script's current working directory, which is where files will be accessed by default. The final backslash is not included unless it is the root directory. Two examples: C:\ and C:\My Documents.

Use SetWorkingDir or assign a path to A_WorkingDir to change the working directory.

The script's working directory defaults to A_ScriptDir, regardless of how the script was launched.

A_InitialWorkingDir The script's initial working directory, which is determined by how it was launched. For example, if it was run via shortcut -- such as on the Start Menu -- its initial working directory is determined by the "Start in" field within the shortcut's properties.
A_ScriptDir The full path of the directory where the current script is located. The final backslash is omitted (even for root directories).
A_ScriptName Read/write: The default title for MsgBox, InputBox, FileSelect, DirSelect and GuiCreate. If not set by the script, it defaults to the file name of the current script, without its path, e.g. MyScript.ahk.
A_ScriptFullPath The full path of the current script, e.g. C:\My Documents\My Script.ahk
A_ScriptHwnd The unique ID (HWND/handle) of the script's hidden main window.
A_LineNumber

The number of the currently executing line within the script (or one of its #Include files). This line number will match the one shown by ListLines; it can be useful for error reporting such as this example: MsgBox Could not write to log file (line number %A_LineNumber%).

Since a compiled script has merged all its #Include files into one big script, its line numbering may be different than when it is run in non-compiled mode.

A_LineFile The full path and name of the file to which A_LineNumber belongs, which will be the same as A_ScriptFullPath unless the line belongs to one of a non-compiled script's #Include files.
A_ThisFunc The name of the user-defined function that is currently executing (blank if none); for example: MyFunction. See also: IsFunc()
A_ThisLabel The name of the label (subroutine) that is currently executing (blank if none); for example: MyLabel. It is updated whenever the script executes Gosub/Return or Goto. It is also updated for automatically-called labels such as timers, GUI threads, menu items, hotkeys and hotstrings. However, A_ThisLabel is not updated when execution "falls into" a label from above; when that happens, A_ThisLabel retains its previous value. See also: A_ThisHotkey and IsLabel()
A_AhkVersion Contains the version of AutoHotkey that is running the script, such as 1.0.22. In the case of a compiled script, the version that was originally used to compile it is reported. The formatting of the version number allows a script to check whether A_AhkVersion is greater than some minimum version number with > or >= as in this example: if (A_AhkVersion >= "1.0.25.07").
A_AhkPath

For non-compiled scripts: The full path and name of the EXE file that is actually running the current script. For example: C:\Program Files\AutoHotkey\AutoHotkey.exe

For compiled scripts: The same as the above except the AutoHotkey directory is discovered via the registry entry HKEY_LOCAL_MACHINE\SOFTWARE\AutoHotkey\InstallDir. If there is no such entry, A_AhkPath is blank.

A_IsCompiled Contains 1 if the script is running as a compiled EXE and an empty string (which is considered false) if it is not.

Date and Time

A_YYYY Current 4-digit year (e.g. 2004). Synonymous with A_Year. Note: To retrieve a formatted time or date appropriate for your locale and language, use FormatTime, OutputVar (time and long date) or FormatTime, OutputVar,, LongDate (retrieves long-format date).
A_MM Current 2-digit month (01-12). Synonymous with A_Mon.
A_DD Current 2-digit day of the month (01-31). Synonymous with A_MDay.
A_MMMM Current month's full name in the current user's language, e.g. July
A_MMM Current month's abbreviation in the current user's language, e.g. Jul
A_DDDD Current day of the week's full name in the current user's language, e.g. Sunday
A_DDD Current day of the week's 3-letter abbreviation in the current user's language, e.g. Sun
A_WDay Current 1-digit day of the week (1-7). 1 is Sunday in all locales.
A_YDay Current day of the year (1-366). The value is not zero-padded, e.g. 9 is retrieved, not 009. To retrieve a zero-padded value, use the following: FormatTime, OutputVar,, YDay0.
A_YWeek Current year and week number (e.g. 200453) according to ISO 8601. To separate the year from the week, use SubStr. Precise definition of A_YWeek: If the week containing January 1st has four or more days in the new year, it is considered week 1. Otherwise, it is the last week of the previous year, and the next week is week 1.
A_Hour Current 2-digit hour (00-23) in 24-hour time (for example, 17 is 5pm). To retrieve 12-hour time as well as an AM/PM indicator, follow this example: FormatTime, OutputVar, , h:mm:ss tt
A_Min

Current 2-digit minute (00-59).

A_Sec Current 2-digit second (00-59).
A_MSec Current 3-digit millisecond (000-999). To remove the leading zeros, follow this example: Milliseconds := A_MSec + 0.
A_Now The current local time in YYYYMMDDHH24MISS format. Note: Date and time math can be performed with DateAdd and DateDiff. Also, FormatTime can format the date and/or time according to your locale or preferences.
A_NowUTC The current Coordinated Universal Time (UTC) in YYYYMMDDHH24MISS format. UTC is essentially the same as Greenwich Mean Time (GMT).
A_TickCount

The number of milliseconds since the computer was rebooted. By storing A_TickCount in a variable, elapsed time can later be measured by subtracting that variable from the latest A_TickCount value. For example:

StartTime := A_TickCount
Sleep, 1000
ElapsedTime := A_TickCount - StartTime
MsgBox,  %ElapsedTime% milliseconds have elapsed.

If you need more precision than A_TickCount's 10ms, use QueryPerformanceCounter().

Script Settings

A_IsSuspended Contains 1 if the script is suspended and 0 otherwise.
A_IsPaused Contains 1 if the thread immediately underneath the current thread is paused. Otherwise it contains 0.
A_IsCritical Contains 0 if Critical is off for the current thread. Otherwise it contains an integer greater than zero, namely the message-check frequency being used by Critical. Since Critical 0 turns off critical, the current state of Critical can be saved and restored via Old_IsCritical := A_IsCritical followed later by Critical %Old_IsCritical%.
A_TitleMatchMode Read/write: The current mode set by SetTitleMatchMode: 1, 2, 3, or RegEx.
A_TitleMatchModeSpeed Read/write: The current match speed (fast or slow) set by SetTitleMatchMode.
A_DetectHiddenWindows Read/write: The current mode (On or Off) set by DetectHiddenWindows.
A_DetectHiddenText Read/write: The current mode (On or Off) set by DetectHiddenText.
A_StringCaseSense Read/write: The current mode (On, Off, or Locale) set by StringCaseSense.
A_FileEncoding Read/write: The default encoding for various commands; see FileEncoding.
A_SendMode Read/write: The current mode (Event, Input, Play or InputThenPlay) set by SendMode.
A_SendLevel Read/write: The current SendLevel setting (an integer between 0 and 100, inclusive).
A_StoreCapslockMode Read/write: The current mode (On or Off) set by SetStoreCapslockMode.
A_KeyDelay
A_KeyDuration
Read/write: The current delay or duration set by SetKeyDelay (always decimal, not hex).
A_KeyDelayPlay
A_KeyDurationPlay
Read/write: The current delay or duration set by SetKeyDelay for the SendPlay mode (always decimal, not hex).
A_WinDelay Read/write: The current delay set by SetWinDelay (always decimal, not hex).
A_ControlDelay Read/write: The current delay set by SetControlDelay.
A_MouseDelay
A_MouseDelayPlay
Read/write: The current delay set by SetMouseDelay (always decimal, not hex). A_MouseDelay is for the traditional SendEvent mode, whereas A_MouseDelayPlay is for SendPlay.
A_DefaultMouseSpeed Read/write: The current speed set by SetDefaultMouseSpeed.
A_CoordModeToolTip
A_CoordModePixel
A_CoordModeMouse
A_CoordModeCaret
A_CoordModeMenu
Read/write: The current mode (Window, Client or Screen) set by CoordMode.
A_RegView Read/write: The current registry view as set by SetRegView.
A_IconHidden Contains 1 if the tray icon is currently hidden or 0 otherwise. The icon can be hidden via #NoTrayIcon or the Menu command.
A_IconTip Blank unless a custom tooltip for the tray icon has been specified via Menu, Tray, Tip -- in which case it's the text of the tip.
A_IconFile Blank unless a custom tray icon has been specified via Menu, tray, icon -- in which case it's the full path and name of the icon's file. Known limitation: This path may be incorrect if the script originally passed a relative path to a system DLL; for example, Menu, Tray, Icon, user32.dll, 2.
A_IconNumber Blank if A_IconFile is blank. Otherwise, it's the number of the icon in A_IconFile (typically 1).

User Idle Time

A_TimeIdle The number of milliseconds that have elapsed since the system last received keyboard, mouse, or other input. This is useful for determining whether the user is away. Physical input from the user as well as artificial input generated by any program or script (such as the Send or MouseMove commands) will reset this value back to zero. Since this value tends to increase by increments of 10, do not check whether it is equal to another value. Instead, check whether it is greater or less than another value. For example:
if A_TimeIdle > 600000
    MsgBox, The last keyboard or mouse activity was at least 10 minutes ago.
A_TimeIdlePhysical

Similar to above but ignores artificial keystrokes and/or mouse clicks whenever the corresponding hook (keyboard or mouse) is installed; that is, it responds only to physical events. (This prevents simulated keystrokes and mouse clicks from falsely indicating that a user is present.) If neither hook is installed, this variable is equivalent to A_TimeIdle. If only one hook is installed, only its type of physical input affects A_TimeIdlePhysical (the other/non-installed hook's input, both physical and artificial, has no effect).

Hotkeys, Hotstrings, and Custom Menu Items

A_ThisMenuItem The name of the most recently selected custom menu item (blank if none).
A_ThisMenu The name of the menu from which A_ThisMenuItem was selected.
A_ThisMenuItemPos A number indicating the current position of A_ThisMenuItem within A_ThisMenu. The first item in the menu is 1, the second is 2, and so on. Menu separator lines are counted. This variable is blank if A_ThisMenuItem is blank or no longer exists within A_ThisMenu. It is also blank if A_ThisMenu itself no longer exists.
A_ThisHotkey

The most recently executed hotkey or non-auto-replace hotstring (blank if none), e.g. #z. This value will change if the current thread is interrupted by another hotkey, so be sure to copy it into another variable immediately if you need the original value for later use in a subroutine.

When a hotkey is first created -- either by the Hotkey command or a double-colon label in the script -- its key name and the ordering of its modifier symbols becomes the permanent name of that hotkey, shared by all variants of the hotkey.

See also: A_ThisLabel

A_PriorHotkey Same as above except for the previous hotkey. It will be blank if none.
A_PriorKey The name of the last key which was pressed prior to the most recent key-press or key-release, or blank if no applicable key-press can be found in the key history. All input generated by AutoHotkey scripts is excluded. For this variable to be of use, the keyboard or mouse hook must be installed and key history must be enabled.
A_TimeSinceThisHotkey The number of milliseconds that have elapsed since A_ThisHotkey was pressed. It will be -1 whenever A_ThisHotkey is blank.
A_TimeSincePriorHotkey The number of milliseconds that have elapsed since A_PriorHotkey was pressed. It will be -1 whenever A_PriorHotkey is blank.
A_EndChar The ending character that was pressed by the user to trigger the most recent non-auto-replace hotstring. If no ending character was required (due to the * option), this variable will be blank.

Operating System and User Info

A_ComSpec Contains the same string as the environment's ComSpec variable (e.g. C:\Windows\system32\cmd.exe). Often used with Run/RunWait.
A_Temp The full path and name of the folder designated to hold temporary files (e.g. C:\DOCUME~1\UserName\LOCALS~1\Temp). It is retrieved from one of the following locations (in order): 1) the environment variables TMP, TEMP, or USERPROFILE; 2) the Windows directory.
A_OSVersion

The version number of the operating system, in the format "major.minor.build". For example, Windows 7 SP1 is 6.1.7601.

Applying compatibility settings in the AutoHotkey executable or compiled script's properties causes the OS to report a different version number, which is reflected by A_OSVersion.

A_Is64bitOS Contains 1 (true) if the OS is 64-bit or 0 (false) if it is 32-bit.
A_PtrSize Contains the size of a pointer, in bytes. This is either 4 (32-bit) or 8 (64-bit), depending on what type of executable (EXE) is running the script.
A_Language The system's default language, which is one of these 4-digit codes.
A_ComputerName The name of the computer as seen on the network.
A_UserName The logon name of the user who launched this script.
A_WinDir The Windows directory. For example: C:\Windows
A_ProgramFiles

The Program Files directory (e.g. C:\Program Files or C:\Program Files (x86)). This is usually the same as the ProgramFiles environment variable.

On 64-bit systems (and not 32-bit systems), the following applies:

  • If the executable (EXE) that is running the script is 32-bit, A_ProgramFiles returns the path of the "Program Files (x86)" directory.
  • For 32-bit processes, the ProgramW6432 environment variable contains the path of the 64-bit Program Files directory. On Windows 7 and later, it is also set for 64-bit processes.
  • The ProgramFiles(x86) environment variable contains the path of the 32-bit Program Files directory.
A_AppData The full path and name of the folder containing the current user's application-specific data. For example: C:\Documents and Settings\Username\Application Data
A_AppDataCommon The full path and name of the folder containing the all-users application-specific data.
A_Desktop The full path and name of the folder containing the current user's desktop files.
A_DesktopCommon The full path and name of the folder containing the all-users desktop files.
A_StartMenu The full path and name of the current user's Start Menu folder.
A_StartMenuCommon The full path and name of the all-users Start Menu folder.
A_Programs The full path and name of the Programs folder in the current user's Start Menu.
A_ProgramsCommon The full path and name of the Programs folder in the all-users Start Menu.
A_Startup The full path and name of the Startup folder in the current user's Start Menu.
A_StartupCommon The full path and name of the Startup folder in the all-users Start Menu.
A_MyDocuments The full path and name of the current user's "My Documents" folder. Unlike most of the similar variables, if the folder is the root of a drive, the final backslash is not included. For example, it would contain M: rather than M:\
A_IsAdmin

If the current user has admin rights, this variable contains 1. Otherwise, it contains 0.

To have the script restart itself as admin (or show a prompt to the user requesting admin), use Run *RunAs. However, note that running the script as admin causes all programs launched by the script to also run as admin. For a possible alternative, see the FAQ.

A_ScreenWidth
A_ScreenHeight

The width and height of the primary monitor, in pixels (e.g. 1024 and 768).

To discover the dimensions of other monitors in a multi-monitor system, use SysGet.

To instead discover the width and height of the entire desktop (even if it spans multiple monitors), use the following example:

SysGet, VirtualWidth, 78
SysGet, VirtualHeight, 79

In addition, use SysGet to discover the work area of a monitor, which can be smaller than the monitor's total area because the taskbar and other registered desktop toolbars are excluded.

A_ScreenDPI Number of pixels per logical inch along the screen width. In a system with multiple display monitors, this value is the same for all monitors. On most systems this is 96; it depends on the system's text size (DPI) setting. See also the GUI's -DPIScale option.
A_IPAddress1 through 4 The IP addresses of the first 4 network adapters in the computer.

Misc.

A_Cursor

The type of mouse cursor currently being displayed. It will be one of the following words: AppStarting, Arrow, Cross, Help, IBeam, Icon, No, Size, SizeAll, SizeNESW, SizeNS, SizeNWSE, SizeWE, UpArrow, Wait, Unknown. The acronyms used with the size-type cursors are compass directions, e.g. NESW = NorthEast+SouthWest. The hand-shaped cursors (pointing and grabbing) are classified as Unknown.

A_CaretX
A_CaretY

The current X and Y coordinates of the caret (text insertion point). The coordinates are relative to the active window unless CoordMode is used to make them relative to the entire screen. If there is no active window or the caret position cannot be determined, these variables are blank.

The following script allows you to move the caret around to see its current position displayed in an auto-update tooltip. Note that some windows (e.g. certain versions of MS Word) report the same caret position regardless of its actual position.

SetTimer, WatchCaret, 100
return
WatchCaret:
  ToolTip, X%A_CaretX% Y%A_CaretY%, A_CaretX, A_CaretY - 20
return
A_EventInfo

Contains additional information about the following events:

Note: Unlike variables such as A_ThisHotkey, each thread retains its own value for A_EventInfo. Therefore, if a thread is interrupted by another, upon being resumed it will still see its original/correct values in these variables.

Read/write: A_EventInfo can also be set by the script, but can only accept unsigned integers within the range available to pointers (32-bit or 64-bit depending on the version of AutoHotkey).

Clipboard Read/write: The contents of the OS's clipboard, which can be read or written to. See the Clipboard section.
ClipboardAll Read-only: The entire contents of the clipboard (such as formatting and text). See ClipboardAll.
ErrorLevel Read/write: See ErrorLevel.
A_LastError

Read/write: This is usually the result from the OS's GetLastError() function after the script calls certain commands/functions, or the HRESULT of the last COM object invocation. See DllCall() or Run/RunWait for more details.

Assigning a value to A_LastError also causes the OS's SetLastError() function to be called.

Loop

A_Index Read/write: This is the number of the current loop iteration (a 64-bit integer). For example, the first time the script executes the body of a loop, this variable will contain the number 1. For details see Loop or While-loop.
A_LoopFileName, etc. This and other related variables are valid only inside a file-loop.
A_LoopRegName, etc. This and other related variables are valid only inside a registry-loop.
A_LoopReadLine See file-reading loop.
A_LoopField See parsing loop.

Environment Variables vs. "Normal" Variables

Environment variables are maintained by the operating system. You can see a list of them at the command prompt by typing SET then pressing Enter. Use EnvGet or EnvSet to retrieve or set environment variable.

A script may create a new environment variable or change the contents of an existing one with EnvSet. However, such additions and changes are private; they are not seen by the rest of the system. One exception is when a script uses Run or RunWait to launch a program (even another script): such programs inherit a copy of the parent script's environment variables, including private ones.

Variable Capacity and Memory