GuideStar provides information on more than 1.8 million American nonprofit organisations. For each NGO, it lists which projects are financed and how. Users can write a review of nonprofits and leave feedback. GuideStar gets NGOs to publish all data in full, and also to exchange between themselves. Organisations can themselves enter and update their mission, their programmes, members and activities online. GuideStar then supplements this information with data from other sources. GuideStar has been a pioneer in the transparency and assessment of NGOs in the USA, and has become an important reference point for many donors.