OpenWPM

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What OpenWPM actually does

The web-measurement platform behind a large share of the papers in this section: an instrumented browser plus a crawl harness plus a schema for the data it collects.

What OpenWPM's maintenance signals mean

The liveness field here is pushed_at, read as 2026-08-06 against a field check 8 days later. That is inside 90 days, and 90 days is where the second edition of the rubric put ACTIVE after moving it down from the first edition's 180.

The reason for the move is worth stating, because it is the kind of threshold that looks arbitrary until you know what it is measuring against: detection changes on a shorter cycle than half a year, so a six-month-old evasion is not a current one. What a recent push does not tell you is what was in it. A commit landing on a branch is not a release, not a fix, and not a test — it is evidence that somebody is still there.

No release was captured for this entry, which this register records as unknown rather than as none. The distinction matters more than it looks: a project with no tags and a project whose tags the sweep failed to read produce the same blank cell, and printing them as the same fact would be the register asserting something it has not measured.

Where OpenWPM sits in this catalogue

OpenWPM is filed in section 05, academic papers & technical writeups, whose scope is this: The peer-reviewed and specification-grade literature this field is built on, preferring open mirrors over publishers that block automated clients. An entry sits in exactly one section here. Where a project could defensibly go in two, it is placed where a reader would look for it first rather than where it fits most tidily, and that is an editorial decision rather than a measured one.

Filed beside it in the same section: Akamai — Passive Fingerprinting of HTTP/2 Clients (ACTIVE), TUM/LRZ — Fingerprinting HTTP/2 (ACTIVE), Antoine Vastel's blog (ACTIVE). Comparing an entry against its own section-mates is more informative than comparing it against the catalogue as a whole, because everything in a section is answering roughly the same question and the differences left over are the ones that matter.

It is published under NOASSERTION, alongside the rest of the NOASSERTION entries in this register, and it sits with everything else currently marked ACTIVE. Read those two facets together: a permissively licensed project that stopped shipping is not a safer dependency than a copyleft one that did not, and a filter on one axis alone will tell you the wrong thing.

Substitutes for the same job, with no claim that either is better: Englehardt & Narayanan — 1-Million-Site Measurement. The alternative relation is symmetric and carries no ranking, because this register publishes no ranking of any kind. The full OpenWPM comparison table sets all of them side by side on licence, push date, release cadence and state.

What to settle before you adopt OpenWPM

It is research infrastructure, and its operational assumptions — scale, storage, browser version pinning — are those of a research crawl rather than a production scraper. Its licence resolves to NOASSERTION and is worth reading directly.