How to set up and use an API key?

What is an API key?

Like many other R packages that are API clients, rromeo lets you set up and use an API key. An API key is a string that you communicate to the server (see Wikipedia Page). The key is used by the server to identify you. This helps the server to manage your access, for example, giving access to specific services.

Why use one?

Many APIs have a limit in the number of queries you can make in a given amount of time. Using an API key, because it identifies you, lets you go over this limit so the server knows it is not under a Denial of Service (DoS) attack. SHERPA/RoMEO has a limit of 500 queries per day without an API key. Registering for an API key lets you exceed this limit.

Registering for an API key for SHERPA/RoMEO

You can register a free API key at You have to provide your name, your job title as well as a valid email address to register for an API key.

It is considered good practice to register one API key per project (e.g. software or research project), in order to avoid making too many queries to the API. Do fill out the description of your application to help the people who made SHERPA/RoMEO data freely available make statistics.

How to set up your API key in rromeo

Now that you have registered for an API key, you can use it in rromeo. There are several ways to set up your API key in rromeo.

Using Sys.setenv() during an interactive session

One way to set up your API key without using the key argument is to use environment variables. Environment variables are system or user-defined variables that are used to store information during your R session.

rromeo searches the environment variable SHERPAROMEO_KEY to check if an API key has been defined. You can access it using the function Sys.getenv() with the name of the variable as as a string:


If none has been defined it should return "". You can then set the environment variable using the function Sys.setenv():

It is set up for the rest of your R session and rromeo will automatically use it when you call the different functions. You can also use the check_key() function that should give the same result if your key is well set-up:

Using the dedicated function rr_auth()

rromeo provides the function rr_auth() that creates a well named environmental variable that can be used in the rest of your session:

This works so that you don’t have to specify the name of the environmental variable by hand. Under the hood rr_auth() uses the same mechanism as explained in the above mentioned section.

Setting up your API key in an .Rprofile file

Every time R starts it looks for .Rprofile files in different locations:

R only loads one .Rprofile file per session and thus an .Rprofile file at the project-level overrides files in other locations.

The .Rprofile file is an R script that is launch each time R starts. Put it at the root of your project and type the following:


You can then reload your session and check that rromeo managed to get your key by using the check_key() function:

Now rromeo can use your SHERPA/RoMEO API key! See the getting started vignette for usage of rromeo functions.

Setting up your API key in an .Renviron file

.Renviron file follow the same loading rules as .Rprofile files, the only difference is that it is is a file whose only purpose is to store environment variables. To use your API key in an .Renviron you have to type the following (note the absence of quotes):


You can then check that your key has been found using check_key():

Now rromeo can use your SHERPA/RoMEO API key! See the getting started vignette for usage of rromeo functions.