A line is considered empty if it contains no characters at all, or only invisible whitespace characters such as spaces, tabs, or non-breaking spaces. With the "Remove blank lines" option enabled, all such lines are eliminated. If you also activate "Trim whitespace", lines that originally contained only spaces become empty and are removed.

Yes. Simply turn off "Remove blank lines" and those lines will be preserved. If you still want to trim spaces from other lines, you can keep "Trim whitespace" on – but note that lines with only spaces will then become completely empty and will remain as empty lines (or be collapsed if you use the compress feature).

Absolutely. This tool runs entirely inside your web browser. No data is ever sent to any server, and no one can access your text. You can safely process sensitive content without worry.

The tool works well for texts up to a few hundred thousand lines on most devices. Performance depends on your device's memory and processor. For extremely large files (tens of megabytes), you might consider using desktop text editors, but typical use cases run instantly.

This particular tool focuses on line-level whitespace (empty lines and leading/trailing spaces). To collapse multiple spaces into one inside a line, you would need a more advanced “normalize whitespace” function. However, the “Trim whitespace” option already cleans up the beginnings and ends of each line.

The output always uses standard newline characters (LF). If your input came from Windows (CRLF), the processing will treat lines correctly, and the output will be LF-only, which is compatible with almost all modern systems and code editors.