LERA¹ is an interactive, web-based working environment for examining similarities and differences between several versions of a text (text comparison and collation). LERA divides the texts into passages and compares in different ways based on user selection, from sentences to single words. Differences are highlighted in color and broken down in a common variant apparatus so that they can be easily localized. With the CATview overview bar, interactive word clouds and clever search functionality, the tool offers various approaches for efficiently exploring text differences. This effectively supports the understanding and ultimately the comprehension of the author's intention when making changes. LERA was developed for collation as a basis for the creation of historical-critical editions.