This paper provides an in-depth analysis of the semantic and syntactic properties of all-clefts ( All I ate for dinner was a salad). The main characteristic of all-clefts is the inference that what is designated by the cleft is not much (the “smallness effect”). On the basis of novel observations on all-clefts with multi-clausal precopular clauses, and the interaction with negation and questions, I argue for three claims: (i) the word all is the head of a relative clause (not a free relative), (ii) the precopular clause is derived by syntactic movement, and (iii) the source of the smallness effect is the mirativity of only ( Beaver & Clark 2008; Zeevat 2009). The little formal work that exists on all-clefts ( Homer 2019) does not offer an analysis that reflects these three claims. Instead I propose a derivational account of all-clefts based on Boeckx ( 2007).