Chapter 5 Rate limits

Scopus: 20,000 per 7 days. See for rate limit information. To see what your personal rate limit details are, request verbose HTTP request output - this will vary on the function you are using - see the docs for the function. See the response headers X-RateLimit-Limit, X-RateLimit-Remaining, and X-RateLimit-Reset (your limit, those requests remaining, and UTC date/time it will reset)

Microsoft: 10,000 per month, and 1 per second. There are no rate limit headers, sorry :(

PLOS: There are no known rate limits for PLOS, though if you do hit something let us know.

Crossref: From time to time Crossref needs to impose rate limits to ensure that the free API is usable by all. Any rate limits that are in effect will be advertised in the X-Rate-Limit-Limit and X-Rate-Limit-Interval HTTP headers. This boils down to: they allow X number of requests per some time period. The numbers can change so we can’t give a rate limit that will always be in effect. If you’re curious pass in verbose = TRUE to your function call, and you’ll get headers that will display these rate limits. See also Authentication.

Semantic Scholar: Not documented in their docs, and no response headers given. At time of this writing (2020-07-01) the rate limit is: 100 requests per 5-minutes per IP address. or 20 requests per min. Note that this rate limit may change.