Source: Roblox Creator Hub · CC BY 4.0 · View source · Code samples: MIT Imported 2026-10-03. Formatting adapted for this site.
debug
Provides a few basic functions for debugging code in Roblox. Unlike the debug library found in Lua natively, this version has been heavily sandboxed.
Functions
| Name | Type / Returns | Description |
|---|---|---|
| debug.traceback | string | Returns a string of undefined format that describes the current function call stack. |
| debug.traceback | string | Returns a string of undefined format that describes the current function call stack. |
| debug.info | Tuple | Traverses the entire stack of current thread and returns a string containing the call stack of target level details. |
| debug.info | Tuple | Traverses the entire stack of current thread and returns a string containing the call stack of target function details. |
| debug.info | Tuple | Traverses the entire stack of target thread and returns a string containing the call stack of target level details. |
| debug.profilebegin | () | Starts profiling for a label. |
| debug.profileend | () | Stops profiling for the most recent label that debug.profilebegin() opened. |
| debug.getmemorycategory | string | Returns the name of the current thread's active memory category. |
| debug.setmemorycategory | string | Assigns a custom tag to the current thread's memory category. |
| debug.resetmemorycategory | () | Resets the tag assigned by debug.setmemorycategory() to the automatically assigned value (typically, the script name). |
| debug.dumpcodesize | () | Displays a table of native code size of individual functions and scripts. |
debug.traceback
Returns a traceback of the current function call stack as a string; in other words, a description of the functions that have been called up to this point. During debugging, this behaves like an error stack trace but does not stop execution of the script.
The level parameter specifies what level of the call stack to consider, with 1 being the call of debug.traceback() itself, 2 being the call of the function calling debug.traceback(), and so on. See the code sample below for an example of sequential function calls.
Note that this function will often return inaccurate results (compared to the original source code) and that the format of the returned traceback may change at any time. You should not parse the return value for specific information such as script names or line numbers.
The following example includes sequential function calls; fnB() is called, and it calls fnA() which then calls debug.traceback().
local function fnA()
print(debug.traceback("Specific moment during fnA()"))
end
local function fnB()
fnA()
end
-- Call function fnB() to begin traceback
fnB()Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| message | string | The first line of the returned string. | |
| level | number | 1 | The number of calls "up" the call stack to return. |
Returns
| Type | Description |
|---|---|
| string | Traceback of the current function call stack. |
debug.traceback
Returns a traceback of the current function call stack as a string; in other words, a description of the functions that have been called up to this point. During debugging, this behaves like an error stack trace but does not stop execution of the script.
The level parameter specifies what level of the call stack to consider, with 1 being the call of debug.traceback() itself, 2 being the call of the function calling debug.traceback(), and so on. See the code sample below for an example of sequential function calls.
Note that this function will often return inaccurate results (compared to the original source code) and that the format of the returned traceback may change at any time. You should not parse the return value for specific information such as script names or line numbers.
The following example includes sequential function calls; fnB() is called, and it calls fnA() which then calls debug.traceback().
local function fnA()
print(debug.traceback("Specific moment during fnA()"))
end
local function fnB()
fnA()
end
-- Call function fnB() to begin traceback
fnB()Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| thread | thread | A thread as returned by coroutine.create(). | |
| message | string | The first line of the returned string. | |
| level | number | 1 | The number of calls "up" the call stack to return. |
Returns
| Type | Description |
|---|---|
| string | Traceback of the current function call stack. |
debug.info
Allows programmatic inspection of the call stack. This function differs from debug.traceback() in that it guarantees the format of the data it returns. This is useful for general logging and filtering purposes as well as for sending the data to systems expecting structured input, such as crash aggregation.
local function fnA()
-- Output source identifier ("s") and line ("l") at levels 1 and 2
print(debug.info(1, "sl")) --> fnA() 3
print(debug.info(2, "sl")) --> fnA() 7
end
fnA()Note that this function is similar to debug.getinfo, an unavailable part of the standard Lua library which serves a similar purpose.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| level | number | Determines at what level of the call stack the information returned should describe. A value of 1 represents the function which is calling debug.info(), a value of 2 represents the function that called that function, and so on. | |
| options | string | A string that describes what the returned information should represent. It must only contain 0 or 1 instances of the characters slnaf, each representing a piece of information: - s (string) — The function source identifier, equal to the full name of the script the function is defined in. - l (number) — The line number of the function call represented by level. - n (string) — The name of the function; may be nil for anonymous functions and C functions without an assigned debug name. - a (number, boolean) — Arity of the function, which refers to the parameter count and whether the function is variadic. - f (function) — The function which was inspected. |
Returns
| Type | Description |
|---|---|
| Tuple | One value per character in options, in the order they appear: source identifier (s), line number (l), function name (n), parameter count and whether variadic (a), or the function itself (f). |
debug.info
Allows programmatic inspection of the call stack. This function differs from debug.traceback() in that it guarantees the format of the data it returns. This is useful for general logging and filtering purposes as well as for sending the data to systems expecting structured input, such as crash aggregation.
local function fnA()
end
local function fnB()
end
-- Output line ("l"), name ("n"), and identifier ("f") for both fnA() and fnB()
print(debug.info(fnA, "lnf")) --> 1 fnA function: 0x75e3d3c398a81252
print(debug.info(fnB, "lnf")) --> 5 fnB function: 0x6022a6dc5ccf4ab2Note that this function is similar to debug.getinfo, an unavailable part of the standard Lua library which serves a similar purpose.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| function | function | The function of the call stack which the information returned should describe. | |
| options | string | A string that describes what the returned information should represent. It must only contain 0 or 1 instances of the characters slnaf, each representing a piece of information: - s (string) — The function source identifier, equal to the full name of the script the function is defined in. - l (number) — The line that function is defined on. - n (string) — The name of the function; may be nil for anonymous functions and C functions without an assigned debug name. - a (number, boolean) — Arity of the function, which refers to the parameter count and whether the function is variadic. - f (function) — The function which was inspected. |
Returns
| Type | Description |
|---|---|
| Tuple | One value per character in options, in the order they appear: source identifier (s), line number (l), function name (n), parameter count and whether variadic (a), or the function itself (f). |
debug.info
Allows programmatic inspection of the call stack. This function differs from debug.traceback() in that it guarantees the format of the data it returns. This is useful for general logging and filtering purposes as well as for sending the data to systems expecting structured input, such as crash aggregation.
local function fnA()
-- Output source identifier ("s") and line ("l") at levels 1 and 2
print(debug.info(1, "sl")) --> fnA() 3
print(debug.info(2, "sl")) --> fnA() 7
end
fnA()Note that this function is similar to debug.getinfo, an unavailable part of the standard Lua library which serves a similar purpose.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| thread | thread | A thread as returned by coroutine.create(). | |
| level | number | Determines at what level of the call stack the information returned should describe. A value of 1 represents the function which is calling debug.info(), a value of 2 represents the function that called that function, and so on. | |
| options | string | A string that describes what the returned information should represent. It must only contain 0 or 1 instances of the characters slnaf, each representing a piece of information: - s (string) — The function source identifier, equal to the full name of the script the function is defined in. - l (number) — The line number of the function call represented by level. - n (string) — The name of the function; may be nil for anonymous functions and C functions without an assigned debug name. - a (number, boolean) — Arity of the function, which refers to the parameter count and whether the function is variadic. - f (function) — The function which was inspected. |
Returns
| Type | Description |
|---|---|
| Tuple | One value per character in options, in the order they appear: source identifier (s), line number (l), function name (n), parameter count and whether variadic (a), or the function itself (f). |
debug.profilebegin
Starts profiling for a MicroProfiler label.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| label | string | The text that this MicroProfiler label displays. |
Returns
| Type | Description |
|---|---|
| () |
debug.profileend
Stops profiling for the most recent MicroProfiler label that debug.profilebegin() opened.
Returns
| Type | Description |
|---|---|
| () |
debug.getmemorycategory
Returns the name of the current thread's active memory category.
Returns
| Type | Description |
|---|---|
| string | The current thread's active memory category. |
debug.setmemorycategory
Assigns a custom tag name to the current thread's memory category in the Developer Console. Useful for analyzing memory usage of multiple threads in the same script which would otherwise be grouped together under the same tag/name. Returns the name of the current thread's previous memory category.
Parameters
| Name | Type | Default | Description |
|---|---|---|---|
| tag | string | The custom name to assign to the current thread's memory category in the Developer Console. |
Returns
| Type | Description |
|---|---|
| string | The current thread's previous memory category. |
debug.resetmemorycategory
Resets the tag assigned by debug.setmemorycategory() to the automatically assigned value (typically, the script name).
Returns
| Type | Description |
|---|---|
| () |
debug.dumpcodesize
Displays a table of native code size of individual functions and scripts. This function is only available in the Command Bar in Studio. More details can be found on the Native Code Generation page.
Returns
| Type | Description |
|---|---|
| () |