Text that has been pasted between programs collects double spaces, tabs and trailing blanks that you cannot see but a reader can. This collapses runs of spaces to one, removes tabs, trims the end of every line and reduces a stack of blank lines to a single break — while leaving the paragraph structure standing. Most tools that promise this quietly turn the whole document into one long line, which is a harder problem to fix than the one you started with.
This page loads no libraries at all — the work is done by the browser itself. Your file is read on your own machine and never sent anywhere — open your browser's network tab and watch while you use it.
No, and that is the whole point. The obvious way to write this tool is to replace every run of whitespace with a single space, but whitespace includes the line breaks, so a page of prose comes back as one paragraph. Here the text is handled line by line: spacing inside a line is tidied, the line breaks between paragraphs are left alone, and a stack of three or more blank lines becomes one blank line.
Runs of spaces and tabs inside a line become a single space; spaces and tabs at the start and end of each line go; and three or more consecutive blank lines become one. Nothing else is touched — punctuation, capitalisation and the words themselves come back exactly as they went in.
Yes. Untick "keep paragraph breaks" and every empty line is dropped, leaving a single block of consecutive lines. That is useful for lists and column data; it is usually the wrong choice for prose.
The result line tells you how many characters disappeared. If that number is zero, the text was already clean, which is worth knowing before you go looking for a problem that is not there.
Everything here is free and works the same way — in your browser.