OpenAlex without an API key: 1,000 requests a day, and mailto no longer helps

Checked 2026-09-08 · Academic and code sources

An anonymous call to api.openalex.org comes back with x-ratelimit-limit: 1000 and x-ratelimit-limit-usd: 0.1 — a budget of 1,000 list requests a day per client, resetting at midnight UTC. Adding mailto= does not change either number, so the polite-pool advice still in the docs buys you nothing on the limit. The 100,000-credit figure in the docs is the free-API-key tier, not the anonymous one.

What we saw

Anonymous request returns a credit budget of 1,000 requests and $0.10. Source: https://api.openalex.org/works?filter=publication_year:2023&per-page=2&cursor=* (response headers, 2026-09-08).
x-ratelimit-cost-usd: 0.0001
x-ratelimit-credits-used: 1
x-ratelimit-limit: 1000
x-ratelimit-limit-usd: 0.1
x-ratelimit-onetime-remaining: 0
x-ratelimit-prepaid-remaining-usd: 0
x-ratelimit-remaining: 996
x-ratelimit-remaining-usd: 0.0996
x-ratelimit-reset: 68563

Adding mailto= leaves the limit at 1000 and still costs one credit. Source: https://api.openalex.org/works?per-page=1&mailto=maintainer@opendatanotes.org (response headers, 2026-09-08).
x-ratelimit-limit: 1000
x-ratelimit-limit-usd: 0.1
x-ratelimit-remaining: 994
x-ratelimit-credits-used: 1

A 200-record page costs the same one credit as a 1-record page, so per-page=200 is 200x cheaper per record. Source: https://api.openalex.org/works?per-page=200&select=id&mailto=maintainer@opendatanotes.org (response headers plus meta.cost_usd, 2026-09-08).
x-ratelimit-credits-used: 1
x-ratelimit-cost-usd: 0.0001
cost_usd 0.0001 n 200

per-page above 200 is rejected with HTTP 400 and a plain message. Source: https://api.openalex.org/works?filter=publication_year:2023&per-page=201 (error body, 2026-09-08).
http=400
{"error":"Pagination error.","message":"per-page parameter must be between 1 and 200."}

Offset paging stops dead at 10,000 records; cursor paging is the only way past it. Source: https://api.openalex.org/works?filter=publication_year:2023&per-page=100&page=101 (error body, 2026-09-08).
http=400
{"error":"Pagination error.","message":"Maximum results size of 10,000 records is exceeded. Cursor pagination is required for records beyond 10,000. See: https://developers.openalex.org/guides/page-through-results"}

cursor=* starts the cursor and the next one arrives in meta.next_cursor; meta.page is null on a cursor request. Source: https://api.openalex.org/works?filter=publication_year:2023&per-page=2&cursor=* (meta, 2026-09-08).
{
 "count": 10894484,
 "db_response_time_ms": 21,
 "page": null,
 "per_page": 2,
 "next_cursor": "IlsxMDAuMCwgMTk5NTAsICdodHRwczovL29wZW5hbGV4Lm9yZy9XNDMyMDAxMzkzNiddIg==",
 "groups_count": null,
 "cost_usd": 0.0001
}

The docs page still describes the polite pool and quotes 100,000 credits per day for free users, which is the keyed tier, not what an anonymous call gets. Source: https://raw.githubusercontent.com/ourresearch/openalex-docs/main/how-to-use-the-api/rate-limits-and-authentication.md (lines 19-20 and 75-87, 2026-09-08).
* max **100,000 credits** per day for free users, and also
* max **100 requests** per second (regardless of credit cost).
...
## The polite pool
...
To get into the polite pool, you just have to give us an email where we can contact you.

The command

curl -sS -D - -o body.json 'https://api.openalex.org/works?filter=publication_year:2023&per-page=2&cursor=*' | grep -iE '^x-ratelimit'

x-ratelimit-cost-usd: 0.0001
x-ratelimit-credits-used: 1
x-ratelimit-limit: 1000
x-ratelimit-limit-usd: 0.1
x-ratelimit-onetime-remaining: 0
x-ratelimit-prepaid-remaining-usd: 0
x-ratelimit-remaining: 996
x-ratelimit-remaining-usd: 0.0996
x-ratelimit-reset: 68563
Checked 2026-09-08.

for u in '...?per-page=1' '...?per-page=1&mailto=maintainer@opendatanotes.org' '...?per-page=200&select=id&mailto=...'; do curl -sS -D - -o body.json "$u" | grep -iE '^x-ratelimit-(limit|remaining|credits)'; done

x-ratelimit-limit: 1000
x-ratelimit-remaining: 995
x-ratelimit-credits-used: 1
x-ratelimit-limit: 1000
x-ratelimit-remaining: 994
x-ratelimit-credits-used: 1
x-ratelimit-limit: 1000
x-ratelimit-remaining: 993
x-ratelimit-credits-used: 1
Checked 2026-09-08.

curl -sS 'https://api.openalex.org/works?filter=publication_year:2023&per-page=100&page=101'

{"error":"Pagination error.","message":"Maximum results size of 10,000 records is exceeded. Cursor pagination is required for records beyond 10,000. See: https://developers.openalex.org/guides/page-through-results"}
Checked 2026-09-08.

what you send	x-ratelimit-limit	credits used	records back
per-page=1, no mailto	1000	1	1
per-page=1, mailto=	1000	1	1
per-page=200 + select=id, mailto=	1000	1	200
per-page=201	-	-	HTTP 400, rejected
per-page=100&page=101	-	-	HTTP 400, 10,000-record wall

Limits

- Measured from one IP with no API key. I did not hold a key, so I could not confirm from the wire that a free key raises the limit to 100,000 — that number comes from the docs.
- I did not spend the budget down to zero, so I have not seen the 429 body OpenAlex sends when the credits run out.
- x-ratelimit-reset counted down by one per second across consecutive calls (68563, 68561, 68555) and 68563 s from the time of the call lands on the next midnight UTC, which matches the documented reset, but I did not sit through a reset.

Open question

Is the 1,000-credit anonymous budget scoped to the IP, or to the IP plus User-Agent? Two clients behind one address would then share it.

Know something this page does not say? Send it with one GET: https://opendatanotes.org/c?kind=correction&page=openalex-anonymous-1000-requests-per-day&text=… — no account needed. I read everything that comes in, and nothing sent here gets published.

Everything here was run from one machine on the date shown.