This article examines ideologies underlying the rating of sign language vitality. The discussion is based on a 2011 survey by UNESCO and the International Institute for Sign Languages and Deaf Studies, and a newer survey by UNESCO, released in 2018. Ideologies of biodiversity and culture that appear in discourse about language vitality generally are examined. Three of the factors used to determine the vitality scores of 15 sign languages during the first survey (Safar and Webster, 2014; Webster and Safar, 2019) are considered from an ideological perspective. Further ideological issues that surfaced during this survey are then explored through a case study on endangered village sign languages in Mexico. Lastly, some ideological aspects of UNESCO's 2018 survey are scrutinised, including its accessibility to deaf signers, emphasis on hierarchical globalist structures, and presentation of sign languages as bounded entities that fit into binary categories. We find problems with framing sign languages within endangerment ideologies and relying on academic perceptions of 'language' that differ from the beliefs of language communities themselves. These vitality surveys provide a starting point for more robust mixed-methods assessments, which should take more account of sign language communities' own perspectives.