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Common Crawl document-digest bloom filter
Membership filter over payload sha1 digests of document-type captures (PDF ~74%, DOC/XLS/PPT/EPUB and similar) from one Common Crawl crawl's URL index — the ~1% of CC that isn't HTML. CC digests are SHA-1 of the (possibly truncated pre-2025) WARC payload; for static documents this equals the file's raw sha1.
- 30,951,194 sha1 keys (UPPERCASE hex), p = 1e-4, 71 MiB
- Source: CC-MAIN index
content_digestcolumn, filtered by MIME (crawl data © Common Crawl, generously public; this digest compilation CC0) - One crawl only — a document must have been live and crawled that month to appear; more crawls widen coverage
Rebuild
cc_extract_job.py in this repo streams one crawl's CDXJ index
(~1 h locally, $0), cc_digests_to_hex.py converts the base32
digests to hex, ./dcso_bloom_build.py cc.sha1.bloom sha1 builds
the filter.
Format
DCSO bloom filter format (github.com/DCSO/bloom), the same format
CIRCL publishes hashlookup in: 48-byte little-endian u64 header
(version, n, p, k, m, N) followed by the bit array. Keys are hex
digest strings — UPPERCASE for sha1, lowercase for sha256 (the
hashlookup convention). Any DCSO-compatible reader works.
Membership answers are probabilistic: p = 1e-4 false-positive rate, no false negatives. Confirm anything important against the source.
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