Open formats. Offline verification.

1. Capture

Scoop (Harvard Library Innovation Lab) drives a browser and records the raw HTTP request/response bytes as WARC (ISO 28500), packaged as WACZ (ZIP + index + metadata). When a page blocks our identified crawler, a fallback browser session produces a self-contained MHTML snapshot instead, honestly labeled as lower fidelity.

Pages that block servers altogether (bot checks, logins, comments that load only when clicked) can be recorded in the submitter's own browser with ArchiveWeb.page (Webrecorder) and the resulting WACZ dropped into the form. Datum checks every file hash and the extension's signature, reads the recorded pages, and labels the citation as recorded in a browser: the submitter's machine, not Datum's server, fetched those bytes.

2. Custody

Full-fidelity archives are signed per WACZ Auth 0.1.0 (the datum.locker domain certificate + an RFC 3161 timestamp), plus an OpenTimestamps Bitcoin-anchored sidecar. A receipt.json records how the capture was obtained and the hash of every artifact. Verification works offline with openssl, ots verify, and a ZIP tool — if checking an archive required Datum's servers, the custody claim would expire when the company does.

3. Replay

Any WACZ opens in ReplayWeb.page (open source), including via a deep link: https://replayweb.page/?source=<url-to-archive.wacz>. Citation pages embed a self-hosted copy of the player when a full-fidelity WACZ is held.

Limits: pages that call live APIs at render time replay only partially, and browser engine drift can alter layout over decades. The archive preserves what was fetched; it cannot freeze the whole live web.

4. Downstream

A clean markdown rendering of the page's main content is derived for machine pipelines (for obituaries: genealogy extraction into CIDOC-CRM triples). Derivatives are never signed as if they were the archive.