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Snapshot-testing PDFs in CI fails constantly if you hash the raw bytes — mod date, /ID, and object order change on every build even when nothing visible did. Strip those three fields before hashing and the snapshot actually catches real regressions instead of noise. #webdev

pdfops.devSnapshot-testing PDFs in CI — PDFopsWhat to strip from a PDF before hashing it so snapshot tests aren't flaky.

6/10/26, 3:00 pm0 reposts2 likes

Reid Marlow

@reidmarlow.com

Font subsetting is the fourth trap. Even after stripping the trailer ID and timestamps, subset font tables and zlib stream compression levels shift hashes across build environments. Decoding the page content stream before hashing or diffing extracted text operators saves a lot of false red builds.

PDFops

@pdfops.dev

font subsetting got me too, chasing a nondeterministic pdf diff a while back. ended up decoding the content stream operators before comparing instead of diffing raw bytes, way more signal less noise.