Number of spaces that a <Tab> in the file counts for. Also see the :retab command, and the 'softtabstop' option.

Note: Setting 'tabstop' to any other value than 8 can make your file appear wrong in many places, e.g., when printing it. The value must be more than 0 and less than 10000.

There are four main ways to use tabs in Vim:

1. Always keep 'tabstop' at 8, set 'softtabstop' and 'shiftwidth' to 4 (or 3 or whatever you prefer) and use 'noexpandtab'. Then Vim will use a mix of tabs and spaces, but typing <Tab> and <BS> will behave like a tab appears every 4 (or 3) characters.
2. Set 'tabstop' and 'shiftwidth' to whatever you prefer and use 'expandtab'. This way you will always insert spaces. The formatting will never be messed up when 'tabstop' is changed.
3. Set 'tabstop' and 'shiftwidth' to whatever you prefer and use a modeline to set these values when editing the file again. Only works when using Vim to edit the file.
4. Always set 'tabstop' and 'shiftwidth' to the same value, and 'noexpandtab'. This should then work (for initial indents only) for any tabstop setting that people use. It might be nice to have tabs after the first non-blank inserted as spaces if you do this though. Otherwise aligned comments will be wrong when 'tabstop' is changed.

If Vim is compiled with the +vartabs feature then the value of 'tabstop' will be ignored if 'vartabstop' is set to anything other than an empty string.

(default 8)