Why does tab expansion sometimes add fewer spaces than the width?

A tab advances to the next tab stop, not a fixed number of spaces. If the cursor is already partway into a tab column, only the spaces needed to reach the next multiple of the width are added. This matches how editors and terminals render tabs.

Does spaces-to-tabs change spaces inside a line?

No. Only the leading indentation of each line is re-tabbed. Alignment spaces inside a line, such as those lining up the right-hand side of an assignment, are preserved so your code formatting is not corrupted.

Which should I use, tabs or spaces?

It depends on your project's style guide. Python's PEP 8 and many JavaScript styles prefer spaces; Go and the Linux kernel use tabs. The safest rule is to match whatever the existing file already uses.

Will this break a mix of tabs and spaces?

The spaces-to-tabs direction first normalises any tabs already in the indent to spaces using your chosen width, then re-tabs cleanly. This produces consistent indentation even from messy mixed input.

Is anything uploaded?

No. The conversion is plain string processing that runs locally in your browser. Your code never leaves the page.

Tab ↔ Space Converter

Inconsistent indentation — a mix of tabs and spaces, or the wrong tab width — is one of the most common causes of noisy diffs and broken layout. This tool converts cleanly in both directions while respecting how tabs actually behave.

How it works

A tab character does not equal a fixed number of spaces; it advances the cursor to the next tab stop, which is the next column that is a multiple of the tab width. Expansion tracks the current column per line and pads only as far as the next stop:

next_stop = floor(column / width) * width + width
spaces    = next_stop - column

Compressing back to tabs works only on the leading indentation. The indent is first expanded to spaces, then every full group of width spaces becomes one tab, with any remainder left as spaces.

Tips and notes

Set the width to match your editor: 4 is common for many languages, 8 for C and Go-style tabs, 2 for some JavaScript styles.
Use tabs-to-spaces before pasting into tools that render tabs unpredictably, such as web forms or chat.
The compress direction deliberately ignores spaces inside a line so that carefully aligned columns are not destroyed.