Always spaces, never tabs

Objective arguments that decided my personal preference.

published 2020-Oct-23, updated 2024-Feb-16

TLDR: always spaces, never tabs; 2 spaces rather than 4.

Arguments

Objective arguments in favor of spaces over tabs:

• Spaces are both necessary and sufficient. Tabs are not necessary and not sufficient (imagine separating words with tabs). Adding them adds complexity.
• Tabs break when copy-pasting. For example, some terminals and websites render tabs as spaces, usually as 8.
• Distinguishing tabs from spaces requires special editor support. (Rendering special whitespace symbols.)
• Mixing tabs with spaces causes indentation to break in different editors. People will mix them. Plenty of languages and editors don't have autoformatters. It will always stay this way.
• Many environments, such as browsers, use Tab for navigation and don't support insertion of the tab character.

Objective arguments in favor of tabs:

• Configurable visual indentation level.
• Fewer characters. Sometimes fewer keystrokes. (Note: in decent code editors, using spaces takes just as few keystrokes.)

Objective arguments against tabs:

• When copy-pasting code, tabs often get converted to spaces, causing breakage and busywork.
• When copy-pasting code with tabs, some REPLs interpret tabs as completion requests rather than indentation.

Objective arguments in favor of 2 spaces over 4 spaces:

• Fewer characters and keystrokes.
• Easier to type in non-specialized editors, such as chat input boxes, which don't have indentation shortcuts.
• Highly-nested code fits better on the screen. Relevant for markup such as XML. Relevant for side-by-side file viewing and diffing.

Objective arguments in favor of 2 spaces over 1 space:

• Can distinguish from line wrapping. In some editors, when line wrapping is enabled, the secondary lines are intended by 1. With 2-space indentation, you can tell them apart.

Bias

Your preference is influenced by your display pixel density, resolution, OS, font family, font size, eyesight, and habits. Someone with a very large but low-DPI display is likely to prefer 4 spaces. Someone who writes code on a small display, in an IDE that uses 20% of the screen area for the actual code, is likely to prefer 2 spaces.

If you don't have a strong preference, 2 spaces seems like a better default, based on the arguments above.