Comments

Apostrophe Comments

A comment is marked by an apostrophe ('), and ignored when the code executes. Comments help explain your code to future readers, including yourself.

Since all lines starting with a comment are ignored, they can also be used to prevent code from executing (while you debug or refactor). Placing an apostrophe ' before your code turns it into a comment. (This is called commenting out the line.)

Sub InlineDocumentation()
  'Comments start with an "'"

  'They can be place before a line of code, which prevents the line from executing
  'Debug.Print "Hello World"

  'They can also be placed after a statement
  'The statement still executes, until the compiler arrives at the comment
  Debug.Print "Hello World"  'Prints a welcome message

'Comments can have 0 indention....
     '... or as much as needed

  '''' Comments can contain multiple apostrophes ''''

  'Comments can span lines (using line continuations) _
    but this can make for hard to read code

  'If you need to have mult-line comments, it is often easier to 
  'use an apostrophe on each line

  'The continued statement syntax (:) is treated as part of the comment, so 
  'it is not possible to place an executable statement after a comment
  'This won't run : Debug.Print "Hello World"
End Sub

'Comments can appear inside or outside a procedure

REM Comments

Sub RemComments()
  Rem Comments start with "Rem" (VBA will change any alternate casing to "Rem")
  Rem is an abbreviation of Remark, and similar to DOS syntax
  Rem Is a legacy approach to adding comments, and apostrophes should be preferred

  Rem Comments CANNOT appear after a statement, use the apostrophe syntax instead
  Rem Unless they are preceded by the instruction separator token
  Debug.Print "Hello World": Rem prints a welcome message
  Debug.Print "Hello World" 'Prints a welcome message

  'Rem cannot be immediately followed by the following characters "!,@,#,$,%,&"
  'Whereas the apostrophe syntax can be followed by any printable character.

End Sub

Rem Comments can appear inside or outside a procedure

Remarks

Comment Blocks

If you need to comment or uncomment several lines at once, you can use the IDE's Edit Toolbar buttons:

Comment Block - Adds a single apostrophe to the start of all selected lines

(opens new window)

Uncomment Block - Removes the first apostrophe from the start of all selected lines

(opens new window)

Multi-line Comments Many other languages support multi-line block comments, but VBA only allows single-line comments.