web-archive
Library of Congress Web Archives
The Library of Congress's curated web-archiving program: more than a hundred thematic collections of websites selected by its librarians, at petabyte scale. You browse the collections on loc.gov, and collection and item pages can also be fetched as JSON. It shines when your topic matches one of the curated themes, elections, events, organizations, rather than for looking up arbitrary URLs.
Why it’s useful & how it works
The Library of Congress web archive rewards researchers whose topic aligns with one of its curated themes: elections, major events, government programs, cultural organizations, and similar subjects selected by LoC librarians. You browse the collections on loc.gov, where each collection lists its member sites, and individual collection and item pages can also be retrieved as structured JSON by appending a query parameter. It is not designed for looking up arbitrary URLs; its strength is depth of coverage within carefully defined themes built up over years.
What’s inside
The program holds more than 100 curated thematic collections at approximately four petabytes of data, a figure that has roughly doubled since 2019 as collecting methods expanded.
API access
loc.gov JSON: append ?fo=json to collection/item URLs.
What we measured
Our own probes, not the archive’s own claims. Re-run periodically; every reading below is dated.
Reachability
- Direct request
- Cloudflare challenge HTTP 403 949 ms (just a moment)
- Through a datacenter proxy
- Unreachable 212 ms (fetch failed: Request was cancelled.)
- API collection, direct
- Cloudflare challenge HTTP 403 18 ms (just a moment)
- API collection, through a proxy
- Unreachable 475 ms (fetch failed: Request was cancelled.)
Did a real search return anything?
The request failed · median 267 ms · down during the run
loc.gov answered 403 to both attempts from our direct IP on 2026-08-22: LoC blocks datacenter ranges and now this egress too, and it accepts no proxy. The collection is real; we simply cannot query it from here.
Reachability measured 2026-08-22. Search checked 2026-08-22.
Access
Freely reachable, no key, login, or captcha.