Is it really free to write sheet music here?

Yes. The editor is free, with no usage limits and no account.

Do I need to sign up or install anything?

No. It works in any modern browser on a computer, tablet or phone. Your score is saved in your own browser.

PDF, to print or share, and MusicXML, the standard format that MuseScore, Finale, Sibelius and Dorico open.

Yes. It includes the guitar treble clef (an octave lower), repeat signs and barre marks.

Free use, download formats and guitar.

Is it really free to write sheet music here?: Yes. The editor is free, with no usage limits and no account.
Do I need to sign up or install anything?: No. It works in any modern browser on a computer, tablet or phone. Your score is saved in your own browser.
Which formats can I download?: PDF, to print or share, and MusicXML, the standard format that MuseScore, Finale, Sibelius and Dorico open.
Is it good for guitar?: Yes. It includes the guitar treble clef (an octave lower), repeat signs and barre marks.