gem version Ruby DOI

serrano is a low level client for Crossref APIs


Other Crossref API clients:

Crossref's API issue tracker:


For changes see the Changelog


Methods in relation to Crossref search API routes

  • /works -
  • /members - Serrano.members()
  • /prefixes - Serrano.prefixes()
  • /funders - Serrano.funders()
  • /journals - Serrano.journals()
  • /licenses - Serrano.licenses()
  • /types - Serrano.types()

Additional methods built on top of the Crossref search API:

  • DOI minting agency - Serrano.registration_agency()
  • Get random DOIs - Serrano.random_dois()

Other methods:

Note about searching:

You are using the Crossref search API described at When you search with query terms, on Crossref servers they are not searching full text, or even abstracts of articles, but only what is available in the data that is returned to you. That is, they search article titles, authors, etc. For some discussion on this, see

Rate limits:

Crossref introduced rate limiting recently. The rate limits apparently vary, so we can't give a predictable rate limit. As of this writing, the rate limit is 50 requests per second. Look for the headers X-Rate-Limit-Limit and X-Rate-Limit-Interval in requests to see what the current rate limits are.

The Polite Pool:

To get in the polite pool it's a good idea now to include a mailto email address. See docs for more information. TLDR: set your email in an env var CROSSREF_EMAIL.

URL Encoding:

We do URL encoding of DOIs for you for all methods except Serrano.citation_count which doesn't work if you encode DOIs beforehand. We use ERB::Util.url_encode to encode.


Release version

gem install serrano

Development version

git clone
cd serrano
rake install


Crossref's API will likely be used by others in the future, allowing the base URL to be swapped out. You can swap out the base URL by passing named options in a block to Serrano.configuration.

This will also be the way to set up other user options, as needed down the road.

Serrano.configuration do |config|
  config.base_url = ""

We recommend you set your mailto email here so you can get in the "polite pool" which gives you faster rate limits:

Serrano.configuration do |config|
  config.mailto = "[email protected]"

Or use an env var with name CROSSREF_EMAIL


Use in a Ruby repl

Search works by DOI

require 'serrano' '10.1371/journal.pone.0033693')

Search works by query string "ecology")

Search works using metadata filters. See CrossRef filter docs. "ecology", filter: { has_abstract: true })

Search journals by publisher name

Serrano.journals(query: "peerj")

Search funding information by DOI

Serrano.funders(ids: ['10.13039/100000001','10.13039/100000015'])

Get agency for a set of DOIs

Serrano.registration_agency(ids: ['10.1007/12080.1874-1746','10.1007/10452.1573-5125'])

Get random set of DOIs

Serrano.random_dois(sample: 100)

Content negotiation

Serrano.content_negotiation(ids: '10.1126/science.169.3946.635', format: "citeproc-json")

Use on the CLI

The command line tool serrano should be available after you install

~$ serrano
  serrano contneg                   # Content negotiation
  serrano funders [funder IDs]      # Search for funders by DOI prefix
  serrano help [COMMAND]            # Describe available commands or one spec...
  serrano journals [journal ISSNs]  # Search for journals by ISSNs
  serrano licenses                  # Search for licenses by name
  serrano members [member IDs]      # Get members by id
  serrano prefixes [DOI prefixes]   # Search for prefixes by DOI prefix
  serrano types [type name]         # Search for types by name
  serrano version                   # Get serrano version
  serrano works [DOIs]              # Get works by DOIs
# A single DOI
~$ serrano works 10.1371/journal.pone.0033693

# Many DOIs
~$ serrano works "10.1007/12080.1874-1746,10.1007/10452.1573-5125"

# output JSON, then parse with e.g., jq
~$ serrano works --filter=has_orcid:true --json --limit=2 | jq '.message.items[].author[].ORCID | select(. != null)'


  • Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms.
  • License: MIT