Methodology
The rule behind everything on this site: a fact without evidence does not ship. Here is exactly what that means.
What counts as a fact
Every entry is a structured claim — “company X runs tool Y in production” — that carries all of the following, or it is not published:
- company + tool + vendor
- canonical product name, vendor listed separately ("Claude" / "Anthropic")
- layer
- exactly one layer from the public taxonomy
- usage
- one line on what the tool actually does for them
- evidence
- at least one receipt: URL, source type, publication date, verbatim quote
- confidence
- high or medium — nothing weaker is published
- status
- current, or historical when they have moved off it
- last verified
- the date the source URL was last confirmed live and still supporting the claim
Quotes are verbatim excerpts of the source, capped at about twenty words — never paraphrased, never reconstructed. If the source does not literally say it, we do not quote it.
Where facts come from
AI stacks are backend-invisible: no crawler can inspect which model or vector database a product calls. So there is no BuiltWith-style detection here — only what companies state in public, ranked by evidentiary value:
- 1
Job postings
"Experience with LangChain / Pinecone required" is dated, first-party proof that a company runs a tool.
- 2
Subprocessor lists & trust centers
Legally maintained vendor lists (GDPR). When a company names its AI vendors here, that is as primary as it gets.
- 3
Engineering blogs
"How we built our RAG pipeline" posts, in the company's own words.
- 4
Vendor case-study pages
Customer stories published by the vendor, inverted into company records. First-party from the vendor side; we date them.
- 5
Podcasts & conference talks
Engineers describing their stack on the record (transcribed). Quoted verbatim from the transcript.
- 6
Public GitHub repos
Dependency files and infra code in repos the company publishes.
- 7
Community threads (HN, Reddit)
Treated as LEADS ONLY — never published from a thread alone; every lead is verified against a source above.
- 8
Self-submission
A bonus signal, never a substitute for public evidence.
Evidence types
Every receipt is tagged with its source type, shown as a badge next to the link:
Confidence levels
A primary source, unambiguous: the company (or its vendor, on the record) states it directly, and the statement is recent enough to trust.
A secondary or dated source: solid evidence, but second-hand or old enough that the stack may have moved on. Shown as-is, labeled as-is.
Dropped. Not hedged, not footnoted — not published. We would rather list 8 well-evidenced facts than 30 weak ones.
Freshness & historical facts
Stack directories die of staleness, so freshness is treated as part of the product. Every fact displays a last verified date — when its source URL was last confirmed live and still supporting the claim — and sources are re-checked on a schedule. When evidence shows a company moved off a tool, the fact is not deleted: it is marked historical and stays visible, because migrations are often the most interesting data point on the page.
The dataset
Everything on this site — every company, fact, and receipt — is available as a single machine-readable JSON export, regenerated on every build. Licensed CC BY 4.0 with attribution to stack.tools.
Download the dataset (stacks.json)Corrections
If you work at a listed company and a fact is wrong or outdated, tell us — we will re-verify against the sources and fix it. Facts that fail re-verification are corrected, marked historical, or removed.
Email a correctionWhat this site does not know
Honest limits: coverage is only as complete as what companies say in public — absence of a tool here is not evidence a company does not use it. Facts can lag reality between re-verification passes. And this site is maintained by an autonomous agent, curated and reviewed by Denis Lunev — the verification gate exists precisely because extraction can be wrong. How that pipeline works is documented on the operations page.