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The OpenAlex API uses a usage-based rate limiting system. Different endpoint types have different costs per request.
API key required starting February 13, 2026. API keys are free—get yours here. See the announcement for details.

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Getting an API Key

API keys are free. Here’s how to get one:
  1. Create a free account at openalex.org
  2. Go to openalex.org/settings/api to get your key
  3. Add api_key=YOUR_KEY to your API calls
curl "https://api.openalex.org/works?api_key=YOUR_KEY"
Without an API key, you’re limited to $0.01/day of usage—enough for quick tests, but not for real work.

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Rate Limits

PlanDaily AllowanceRequests/Second
No API key$0.01100
Free API key$1100
Paid planHigher limits100
Academic researchers can often get increased limits for free—contact support@openalex.org.

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Pricing by Endpoint

TierExampleCost
Singleton — Retrieve by ID or DOI/works/W123 or /works/doi:10.1234/fooFree
List / Filter — Query and filter entities/works?filter=institution.id:I123$0.10 / 1,000 calls
Search — Full-text keyword search/works?search=climate+change$1 / 1,000 calls
Semantic — AI-powered semantic search/works?search.semantic=climate+change$10 / 1,000 calls
Content Download — Cached PDF via content APIcontent.openalex.org/works/{id}.pdf$10 / 1,000 downloads
Text/Aboutness (deprecated)/text/topics$0.01 / call

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What you can do for free every day

With a free API key ($1/day), you can make per day:
  • Unlimited singleton requests (they’re free)
  • 10,000 list/filter requests, or
  • 1,000 search requests, or
  • 100 semantic searches or content downloads, or
  • Any mix totaling $1

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Common Activity Costs

ActivityCallsCost
Download 1,000 PDFs1,000 content downloads$10
Retrieve 1M Works about “Climate Change AND Kelp”~5,000 paginated search calls$5
Retrieve 1M Works by DOI from a list1M singleton callsFree
Filter all Works from an Institution (1M results)~5,000 list calls$0.50
Daily research (20 searches, 200 filters, 50 lookups)270 callsFree

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High-cost endpoints

Some endpoints cost significantly more:
EndpointCostDaily limit (free)Notes
Search$1 / 1,000 calls~1,000 requests?search= query parameter
Semantic search$10 / 1,000 calls~100 requests?search.semantic=
Content downloads$10 / 1,000 files~100 filesPDF or TEI XML
Aboutness (/text)$0.01 / call~100 requestsDeprecated
Planning bulk content downloads? Downloading all 60M available PDFs would cost ~$600,000. Contact us about enterprise pricing for large-scale projects.

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Rate Limit Headers

Every API response includes headers showing your current status:
HeaderDescription
X-RateLimit-LimitYour total daily limit
X-RateLimit-RemainingRemaining for today
X-RateLimit-Credits-UsedCost of this request
X-RateLimit-ResetSeconds until reset (midnight UTC)

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Check Your Status

Check your current rate limit status using the /rate-limit endpoint: 
curl "https://api.openalex.org/rate-limit?api_key=YOUR_KEY"

{
  "api_key": "abc...xyz",
  "rate_limit": {
    "daily_budget_usd": 1,
    "daily_used_usd": 0.05,
    "daily_remaining_usd": 0.95,
    "prepaid_balance_usd": 0,
    "prepaid_remaining_usd": 0,
    "prepaid_expires_at": null,
    "resets_at": "2026-02-20T00:00:00.000Z",
    "resets_in_seconds": 43200,
    "endpoint_costs_usd": {
      "singleton": 0,
      "list": 0.0001,
      "search": 0.001,
      "semantic": 0.01,
      "content": 0.01,
      "text": 0.01
    }
  }
}

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Exceeding Limits

If you exceed your daily limit or make more than 100 requests per second, you’ll get 429 Too Many Requests errors. Best practices:

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Query Limits

Beyond rate limits, individual queries have these constraints:
LimitValue
OR values per filter100
per_page maximum100
sample maximum10,000
Basic paging limit10,000 results
To retrieve more than 10,000 results, use cursor paging.

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Usage Tips

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Browser Testing

The API uses simple GET requests, so you can test any request in your browser. Install a JSON formatter extension for a better experience:

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Efficient Bulk Extraction

# Use maximum page size
requests.get("https://api.openalex.org/works?per_page=100&api_key=YOUR_KEY")

# Batch DOI lookups (up to 100 at once)
dois = "10.1234/a|10.1234/b|10.1234/c"
requests.get(f"https://api.openalex.org/works?filter=doi:{dois}&api_key=YOUR_KEY")