Collapse double spaces, trim line ends and turn tabs into spaces. Nothing leaves your browser.
Collapse runs of spaces to one turns two or more space characters in a row into a single space, so 'a b' becomes 'a b'. Trim spaces at line starts removes spaces and tabs before the first word of each line, which also removes indentation. Trim spaces at line ends removes spaces and tabs after the last word. Turn tabs into spaces replaces each tab with one space. Collapse runs of blank lines to one shrinks a gap of several empty lines to a single blank line. Collapse and both trims are on by default. Tabs and blank-line runs are left alone until you ask.
Per line, the steps run in this order: tabs to spaces, collapse runs, trim the start, trim the end. Blank-line runs are handled last, on the finished lines. Only the space character and the tab are touched. Non-breaking spaces, thin spaces and other invisible characters pass through unchanged, because they often mean something. If you leave the tab switch off, tabs stay, and a mix such as space tab space is not collapsed, since collapsing only looks at runs of plain spaces. Switch tabs on to treat it as three spaces and then one.
A line that holds only spaces or tabs is blank for the blank-line option, whether or not trimming turned it into an empty line. When a run of blank lines is shrunk, the first line of the run is the one kept, as it stands after the other steps. Lines are never joined, so paragraph breaks survive. To delete blank lines completely, use the empty lines page. Windows, old Mac and Unix line endings are each read as one break and written back as plain Unix breaks, and a trailing break at the end of your text is kept.
The result shows how many characters were removed and how many lines there are. A tab replaced by a space removes no character, so it adds nothing to the count. The work happens in this tab and nothing is uploaded. Your switches are remembered in this browser; the text is not. Text up to 1,000,000 characters is handled, and longer text shows a message asking you to split it. For trimming together with other list clean-ups, use the list cleaner.
It reduces two spaces after a full stop to one, which fixes the old typewriter habit. A single space stays, since a single space is never extra.
They are probably tabs, or non-breaking spaces copied from a web page. Switch on Turn tabs into spaces for tabs. Non-breaking spaces are left alone on purpose.
Yes while Trim spaces at line starts is on. Switch it off to keep indentation. With collapse still on, 4 spaces of indent shrink to 1, so switch collapse off too to keep it exactly.
No lines are joined or split. Only the option for runs of blank lines removes whole lines, and then it keeps one of each run.
No. It only removes extra spaces. A single space between words is kept.