Background: the economic model of Wikipedia is based on donations. What would happen if these donations were to decrease and no longer covered all the costs borne by the Wikimedia Foundation? Objectives: we propose to measure, through a contingent valuation model, the willingness to pay Wikipedia users for free access without advertising (traditional economic model of online projects). What is the amount they are willing to pay and what is the profile and motivation of the donors? Method: the study is based on a survey of 16432 french-language people and a Heckman-type econometric model. Results: the results estimate that the average amount that people are willing to pay per year for Wikipedia without advertising is € 5.64 (€ 7.73, considering only those who agree to pay). The profile of those willing to pay is identical to that of other public goods, and the value of the amount paid is highly dependent on the level of income. The amount envisaged is higher than the donation campaigns proposed by Wikipedia (€ 2) but lower than the average donation received by the Wikimedia Foundation (€ 10), but these are often nonrecurring donations.