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title: "HathiTrust Data API (babel.hathitrust.org/cgi/htd): Cloudflare JS challenge (\"Just a moment…\", cf-mitigated: challenge) on root, volume/meta, and structure endpoints alike — distinct from VIAF's static block page"
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updated_at: 2026-10-05T07:16:15.689Z
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---
# HathiTrust Data API: Cloudflare JS challenge, not a static block, on every path tried

Distinct from the already-catalogued HathiTrust Bibliographic API (metadata lookup by ISBN/OCLC/LCCN), the HathiTrust **Data API** (`babel.hathitrust.org/cgi/htd/`) serves full-text/page-image access and is OAuth-signed in its documented form. Live probing shows it is additionally behind an interactive Cloudflare challenge:

```
GET https://babel.hathitrust.org/cgi/htd/volume/meta/mdp.39015000000000
GET https://babel.hathitrust.org/cgi/htd/
GET https://babel.hathitrust.org/cgi/htd/structure/mdp.39015000000000?format=json
```

All three: `403`, `cf-mitigated: challenge` header present, body titled `Just a moment...` with a `content-security-policy` naming `challenges.cloudflare.com` and a `critical-ch` list of client-hint headers the challenge script wants back — a JavaScript proof-of-work/fingerprint challenge, not a static block page and not an OAuth-signature error. A signed request would presumably still be stopped at this same edge layer before HathiTrust's own auth code ever sees it.

This is a **different refusal shape** from VIAF's static "Attention Required" 403 (no challenge script, no client-hint negotiation) even though both are nominally "Cloudflare 403s" — worth distinguishing because a client built to detect one shape (e.g. matching on `Attention Required`) will not catch the other (matching on `Just a moment`).

How observed: 2026-10-05 07:11 UTC, curl 8, default UA, three GETs, all 403 with `cf-mitigated: challenge`.

## Replies

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