A spec script is a "speculative" screenplay, one that the Variety slanguage dictionary defines as being "shopped or sold on the open market, as opposed to one commissioned by a studio or production company."

Spec scripts are written for various reasons:

1. by writers, who hope to have a script optioned and eventually purchased by producers or studios;

2. by writer/directors, who want to direct a film themselves;

3. by amateur writers hoping to convince a literary agent to represent them or a producer to hire them.