The British Library has digitized its collection of 93 copies of the 21 plays by Shakespeare printed in quarto before the theatres were closed in 1642. Shakespeare’s plays appear to have been first printed in 1594. Titus Andronicus was probably the first one. Eighteen of Shakespeare’s plays were published in quarto editions before he died in 1616. Quartos are small and very portable (think modern paperback) books that were made by folding a large sheet of paper into quarters. The first collected “official” printing of Shakespeare’s plays was the 1623 “first folio” edition of 36 plays by Shakespeare. The first folio was a production of Shakespeare’s friends, including actors from his company. The quartos are important because they’re typically the earliest, and hence presumably closest to Shakespeare’s own, versions of the plays. Some of them appear to have been versions that were edited for specific audiences, like the so-called “bad quartos” of Hamlet.