Add Line Numbers
Prefix each line of text with a line number.
Computed on your device — nothing is sent anywhere.
How it works
Prefix each line of text with a line number. Runs 100% in your browser, so your files never leave your device. Free, fast, no signup.
Questions about add line numbers
Yes — no watermark, no daily cap, no signup. Pro raises the file-size and batch limits, but the tool itself is not gated.
No. This tool runs entirely in your browser. Open your network inspector and watch while it works — there are no file uploads, because there is no upload endpoint.
Up to 10 files at 15 MB each. Everything runs in your browser, so the real ceiling is your device’s memory — the cap keeps a large file from exhausting the tab.