As the written word has moved online, new technological affordances and pressures – such as accelerated cycles of production and consumption – have changed how news headlines are produced and selected. Previous literature has linked certain strategies (e.g., clickbait) and linguistic features (e.g., length, negativity) to the success of text online (e.g., clicks). We tracked changes in the prevalence of those features in a sample of ca. 40 million news headlines across the last two decades from English-language outlets worldwide, focusing on the period in which the headline format adapted to the online context. We drew from a broad set of lexical, syntactic and semantic features from the literature to find the signature of the transition to online formats in the journalistic output of the last two decades. Many – but not all – of these features have become more prevalent over time, such as length and negativity. This systematic shift appeared across news outlets from different countries, political leanings, and of different journalistic quality. This may indicate an adaptation to the new affordances and pressures of the digital, online environment, and raises questions for the design of online environments in the future.