Protest size, defined as the number of people a movement brings to the streets to protest, is the one of the strongest predictors of regime concessions. In this paper, I argue that seemingly democratic institutions provide autocratic regimes with information about the size and preferences of the opposition which moderates the effectiveness of increased protest size on concessions. Better information about potential dissent ex ante enables regimes to withstand larger protests without conceding to protesters. To test the argument, data was sourced from the Mass Mobilization in Autocracies database (MMAD) v4, Varieties of Democracy (V-Dem) v12, and Integrated Crisis Early Warnings System (ICEWS). I run country-fixed effects models on a panel of 15650 country-months. I find that the positive effect of increased protest participation on state concessions in autocracies is moderated by democratic institutions that provide regimes with information on the size, strength and preferences of the opposition.