20. Everything is written in English

Date: 2026-09-13

Status

Accepted. Amended on 2026-09-27: the English is American.

Context

The package is public, and a mixed-language repository forces every contributor to switch languages between a file and its documentation.

Decision

Code, public API, XML documentation, project documentation, commit messages, diagnostics and exception messages are all written in English.

The spelling is American throughout: type and member names, package identifiers, command-line verbs, diagnostic codes, corpus manifest keys, documentation and prose alike — color, catalog, license, optimize, behavior, gray. It is the spelling of the .NET base class library and of PDF's own keys (/ColorSpace), so an identifier and the key it names agree. Proper names keep their own spelling (the UK's Open Government License, Etalab's Licence Ouverte, the Xerox WorkCentre), as do text quoted from a document and HTML's aria-labelledby.

Consequences

Recorded so the choice is not silently revisited.

The repository was written in British English until 2026-09-27, when the maintainer chose American English and it was converted in one pass, before any stable release: the identifiers the milestone files plan (PdfColorSpace, PdfOptimizer, the verbs optimize, normalize and sanitize, the optimize.* codes), the corpus manifest's license key, the file names that carried a British spelling, and the prose. No shipped public API carried one; had it, ADR 30 would have allowed the rename in a preview.

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Recorded as D19 before this project adopted Architecture Decision Records; the identifier still appears in commit messages and in CLAUDE.md.