Fused Extended Two-Way Fixed Effects R package fetwfe version 1.10.0 Calculates the fused extended two-way fixed effects (FETWFE) estimator for unbiased and efficient estimation of difference-in-differences in panel data with staggered treatment adoption. This estimator eliminates bias inherent in conventional two-way fixed effects estimators, while also employing a novel bridge regression regularization approach to improve efficiency and yield valid standard errors. Also implements extended TWFE (etwfe) and bridge-penalized ETWFE (betwfe). Provides S3 classes for streamlined workflow and supports flexible tuning (ridge and rank-condition guarantees), automatic covariate centering/scaling, and detailed overall and cohort-specific effect estimates with valid standard errors. Includes simulation and formatting utilities, extensive diagnostic tools, vignettes, and examples. See Faletto (2025) (<doi:10.48550/arXiv.2312.05985>). Software Depends: R (>= 4.1.0) Imports: generics, glmnet, grpreg, Matrix (>= 1.6-0) Suggests: bacondecomp, knitr, rmarkdown, dplyr, did, expm, ggplot2, broom, lme4, testthat (>= 3.0.0), tibble Gregory Faletto <gfaletto@gmail.com> Comprehensive R Archive Network (CRAN) Gregory Faletto [aut, cre] (ORCID: <https://orcid.org/0000-0001-8298-1401>) MIT + file LICENSE (https://CRAN.R-project.org/package=fetwfe/LICENSE) 2026-05-24 application/tgz https://CRAN.R-project.org/package=fetwfe doi:10.32614/CRAN.package.fetwfe