Perceptual hashing & matching

Image and video perceptual hashing and matching — the axis hashkit, hashkit-match, and csam-shield build on. Meta’s PDQ / TMK / vPDQ are upstream of our hashing and our conformance source; we never claim to beat them.

11 projects — 10 learn from · 1 reference.

Project descriptions are adapted from awesome-safety-tools (maintained by ROOST); the verdicts and analysis are ours. Snapshot: June 2026 — a point-in-time view that complements, and does not replace, their living list.

Altitude

Learn from · by Jigsaw (Google) · pairs with hashkit-match

A self-contained reviewer-facing front end over a hash matcher — the same hash-then-action loop a CSAM pipeline runs, just aimed at a different harm vertical. FightCSAM users building a moderation queue on top of hashkit-match can study its review-UI and actioning patterns directly.

A free, open-source web UI and hash-matching tool that helps platforms find and review violent-extremism and terrorism content, drawing on shared industry hash sets.

Hasher-Matcher-Actioner (HMA)

Learn from · by Meta · pairs with csam-shield

The reference end-to-end hash -> match -> act service, and the closest external analogue to CSAM-Shield's orchestration role. A FightCSAM user choosing between adopting HMA wholesale or wiring CSAM-Shield's unified middleware should read this as the leading alternative on the orchestration axis.

A turnkey service that combines a hashing algorithm, a matching function, and the ability to hook into actions, so platforms can stand up content matching end to end.

hma-matrix

Learn from · by Matrix.org · pairs with csam-shield

A real-world example of fitting a generic HMA matcher to one platform's data model and moderation flow. A FightCSAM user integrating CSAM-Shield into a federated or chat platform can mine it for protocol-binding patterns.

Matrix-specific extensions to Meta's HMA, adapting the hasher-matcher-actioner for the Matrix messaging ecosystem.

Lattice Extract

Learn from · by Adobe · pairs with hashkit-match

A precision aid that addresses a known perceptual-hash failure mode — collages and grid layouts that collide spuriously. A FightCSAM user tuning hashkit-match thresholds could pair it as a pre-filter to cut false positives before review.

Grid and lattice detection intended to guard against false positives in hash matching by identifying repeating structured patterns in images.

MediaModeration

Learn from · by Wikimedia · pairs with csam-shield

A production CSAM hash-matching integration built into a specific CMS, with the credentialed-list and review plumbing that implies. A FightCSAM user adding CSAM-Shield to a content platform can study how it sequences upload, match, and escalation.

A MediaWiki extension that performs CSAM hash matching on uploaded media for Wikimedia projects.

PDQ

Learn from · by Meta · pairs with hashkit

The upstream image-hashing standard that the NCMEC Hash Sharing API accepts and that HashKit implements and conforms to — it is our source of truth, not a competitor. A FightCSAM user should treat PDQ as the canonical algorithm and HashKit as the byte-identical, multi-runtime way to run it.

An open-source perceptual hash algorithm for images, producing a compact fingerprint whose Hamming distance approximates visual similarity.

Perception

Learn from · by Thorn · pairs with hashkit

A mature multi-algorithm hashing toolkit covering much of the same ground as HashKit's core, with strong benchmarking and deployment utilities. A FightCSAM user working in Python may reach for Perception's breadth, while HashKit's draw is cross-runtime byte-identical output and NCMEC-verified vectors.

A Python library offering a common wrapper around popular perceptual hashes (such as ImageHash), with tooling to benchmark and deploy them.

RocketChat CSAM

Learn from · by Prostasia Foundation · pairs with csam-shield

A concrete CSAM hash-matching plug-in for one chat platform, showing what it takes to retrofit detection into existing self-hosted software. A FightCSAM user running Rocket.Chat-style infrastructure can compare it against wiring CSAM-Shield's middleware directly.

An integration that adds CSAM hash matching to Rocket.Chat deployments.

TMK+PDQF

Learn from · by Meta · pairs with hashkit

The upstream video-hashing standard accepted by the NCMEC Hash Sharing API, and one of the algorithms HashKit implements and conforms to — our reference, never something we claim to beat. A FightCSAM user needs TMK+PDQF for known-video matching; HashKit's role is producing identical hashes across every runtime.

An open-source algorithm for visual-similarity matching of videos (TMK+PDQF), producing a fixed-length video fingerprint.

vPDQ

Learn from · by Meta · pairs with hashkit

An upstream PDQ-based approach to video matching that complements TMK, and part of the Meta conformance lineage HashKit follows rather than competes with. A FightCSAM user choosing a video-hashing strategy should evaluate vPDQ vs TMK+PDQF on their own merits, with HashKit supplying portable, verified implementations.

An open-source method for visual-similarity matching of videos that applies the PDQ image algorithm frame by frame.

HMA-CLIP demo

Reference · by juanmrad · pairs with csam-shield

A worked example of bolting a new signal type (CLIP embeddings) onto an HMA-style pipeline. Useful to a FightCSAM user weighing how to extend CSAM-Shield beyond perceptual hashing toward classifier or embedding signals.

A demo extending HMA with CLIP embeddings, offered as a reference for how to add new signal/format extensions to the Hasher-Matcher-Actioner.