  Past work in natural language processing interpretability focused mainly on
popular classification tasks while largely overlooking generation settings,
partly due to a lack of dedicated tools. In this work, we introduce Inseq, a
Python library to democratize access to interpretability analyses of sequence
generation models. Inseq enables intuitive and optimized extraction of models'
internal information and feature importance scores for popular decoder-only and
encoder-decoder Transformers architectures. We showcase its potential by
adopting it to highlight gender biases in machine translation models and locate
factual knowledge inside GPT-2. Thanks to its extensible interface supporting
cutting-edge techniques such as contrastive feature attribution, Inseq can
drive future advances in explainable natural language generation, centralizing
good practices and enabling fair and reproducible model evaluations.
