Courtlistener

CourtListener for empirical legal research

Free Law Project's corpus. Three access routes with very different properties, and one distinction that people get wrong before they start.

The two corpora are not the same thing

The tell is on the court record itself: pacer_court_id: null + has_opinion_scraper: true means a scraped state court, not a PACER one. Verified on Delaware Chancery:

GET /api/rest/v4/courts/delch/
  "full_name": "Court of Chancery of Delaware"
  "jurisdiction": "SA"            <- state
  "has_opinion_scraper": true
  "pacer_court_id": null          <- NOT RECAP

Pick the route before writing any code

Default to bulk for research. It is public domain, needs no account, and does not rate-limit you. Reach for the API only when you need data newer than the last quarterly snapshot, or when you want a few hundred records rather than a corpus.

Bulk data

No authentication. Public Domain Mark. Regenerated quarterly on the last day of March, June, September and December. Snapshots, not deltas — each file is the whole table.

https://com-courtlistener-storage.s3-us-west-2.amazonaws.com/?list-type=2&prefix=bulk-data/
aws s3 ls s3://com-courtlistener-storage/bulk-data/ --no-sign-request

Measured sizes, 2026-06-30 snapshot:

Also published: financial disclosures, judges, oral arguments, and ~2 TB of ModernBERT opinion embeddings at s3://com-courtlistener-storage/embeddings/opinions/.

Filter clusters first, then stream opinions. opinion-clusters is 22× smaller and carries the court and date. Select the cluster ids you want, then stream-decompress the 54 GB opinions file and keep only matching rows. Never materialise the opinions CSV.

Files are PostgreSQL COPY TO output: CSV, UTF-8, header row. Schema dumps are published alongside; field definitions are in the CourtListener GitHub models.py, or via an OPTIONS request to the matching API endpoint.

REST API v4

https://www.courtlistener.com/api/rest/v4/

• search and courts work unauthenticated — 3,358 delch opinions were pulled in 206 unauthenticated calls.
• dockets returns {"detail":"Authentication credentials were not provided."} without a token.
• Token lives at /profile/api/ — which sits behind a "Let's confirm you are human" interstitial. That gate is the site's bot check and belongs to Free Law Project; the user clears it, not you.
• Search type params: type=o opinions, type=r RECAP dockets.

Pace politely and back off on 429/5xx. This is a nonprofit's free service; without a token there is no quota to raise, so courtesy is the entire budget.

API Facts

• suitNature is not normalised. The same NOS 160 appears as Stockholders Suits, 160 Contract: Stockholders Suits and 160 Stockholders Suits. Query the text (suitNature:"Stockholders Suits"), not the numeric code, or you silently lose most of the set.
• Derivative suits are docketed under more than one NOS. "shareholder derivative" returns 1,670 under NOS 160 and 2,020 under 850 (Securities/Commodities). Filtering to 160 alone drops more than half.
• docketNumber carries the C.A. number, which joins directly to a Delaware Chancery docket from Lex Machina or CourtConnect — measured at 100% match on 2,350 rows. That join is what lets a filing universe from one source meet a ruling from this one.
• Opinions are written decisions only, and that is a selection, not a gap. Measured against a verified Chancery filing universe: 82% of caption-derivative filings never produce a written opinion, because most dispositions are bench rulings from the transcript. An outcome variable built from opinions describes the selected fifth. Reporting a dismissal rate without that denominator is an unverified claim dressed as a finding.
• The bulk snapshot lags up to a quarter. The 2026-06-30 file lands two weeks after a 2026-06-15 event, so a study of anything recent gets a truncated post-period until the next drop. Check the snapshot date against your event date before designing the test.

Coverage and what is coming

Delaware Chancery: 3,358 opinions since 2012 (delch). Texas currently covers the Supreme Court, Court of Criminal Appeals and the 15 civil courts of appeal.

From the FLP wiki, verbatim:

"In 2026, we are collecting content from high and appellate courts at the five most populous states: California, New York, Texas, Florida, and Pennsylvania."

"In 2027 we aim to continue this with the Delaware Chancery Court and the next most populous states."

The 2027 item is filings, not opinions — Chancery opinions already exist. Docket-level state coverage would reach the bench rulings the opinion corpus structurally cannot see.

Red Flags — STOP if you catch yourself

Related

• ui-json-capture — when the source is a paywalled UI rather than an open corpus
• wrds — the SEC-filing side of the same research questions