---
license: cc-by-4.0
pretty_name: Software Heritage content bloom filters
---

# Software Heritage content membership filters

DCSO-format bloom filters over the content hashes of **all 29,283,034,124
content blobs** in the [Software Heritage](https://www.softwareheritage.org/)
archive (graph dataset export 2026-06-04, `content` table), one
filter per hash scheme, false-positive rate p = 0.0001 each:

| file | keyed on | key encoding |
|---|---|---|
| `swh.sha256.bloom` | sha256 | lowercase hex |

`sha1_git` is the git blob id — membership testing straight from a git
object id, no file bytes needed.

Ask "has SWH archived this content?" without touching the rate-limited
API — then confirm hits at
`https://archive.softwareheritage.org/api/1/content/<scheme>:<hex>/`.
Built for [hashdex](https://github.com/davidar/hashdex) (`hdx scan`),
readable by any DCSO/hashlookup-compatible bloom implementation
(header: LE u64 version, n, p-bits, k, m, N; then bit array;
membership = FNV-1 64 mod 2^64-87, k rounds of wrapping multiply by
18446744073709550147 mod 2^64-87, bit index mod m).

Derived from the Software Heritage graph dataset (CC-BY 4.0,
attribution: Software Heritage). See their
[dataset docs](https://docs.softwareheritage.org/devel/swh-export/graph/dataset.html).