As Web APIs evolve, developers assign them version identifiers to reflect the amount and the nature of changes that the API clients should expect. In this work we focus on identifying versioning practices adopted by Web API developers by extracting and classifying version identifiers found in a large collection of OpenAPI descriptions.
In particular, we observe how frequently different versioning schemes have been adopted for identifying both stable and preview releases (e.g., simple version counters, semantic versioning, or release timestamps). We further study the stability of versioning schemes during APIs evolution. We also detect APIs which offer dynamic access to versioning metadata through dedicated endpoints as well as APIs which support clients expecting to reach up to 14 different versions of the same API at the same time.
Overall the results offer a detailed view over current Web API versioning practices and can serve as the basis for future discussions on how to standardize critical API versioning metadata.