Open Postal Code Correspondence R package OPCC version 1.0.1 An open, fully reproducible alternative to closed postal code conversion files, giving source-qualified many-to-many correspondence between Ontario postal codes and Statistics Canada 2021 census geographies. Every published artifact can be rebuilt step by step from public sources using the included build functions, so any user can reproduce and audit the conversion end to end. Lookup results retain allocation weights, evidence source, lineage, method, and vintage; unmatched postal codes remain explicit, and versioned release artifacts are checksum-verified before use. A built-in 'shiny' application provides a point-and-click interface for joining, mapping, and exporting results. Correspondences are derived from the Statistics Canada National Address Register <https://www150.statcan.gc.ca/n1/pub/46-26-0002/462600022022001-eng.htm>, the 2021 Census Geographic Attribute File <https://www12.statcan.gc.ca/census-recensement/2021/geo/aip-pia/attribute-attribs/index-eng.cfm>, and the GeoNames postal code export <https://download.geonames.org/export/zip/>. The package does not redistribute Canada Post, PCCF, or PCCF+ data and does not claim authoritative postal assignments. Software Depends: R (>= 4.1) Imports: digest, jsonlite Suggests: testthat (>= 3.0.0), curl, dplyr, readr, readxl, rlang, sf, knitr, rmarkdown, withr, shiny (>= 1.8.0), bslib (>= 0.6.0), DT, leaflet, htmlwidgets, chromote, processx, httpuv Lennon Li <yeli@biostats.ai> Comprehensive R Archive Network (CRAN) Lennon Li [aut, cre, cph] MIT + file LICENSE (https://CRAN.R-project.org/package=OPCC/LICENSE) 2026-09-22 application/tgz https://CRAN.R-project.org/package=OPCC doi:10.32614/CRAN.package.OPCC en-US