AbstractLinguistic annotation tools and linguistic annotations are scarcely syntactically and/or semantically interoperable. Their low interoperability usually results from the number of factors taken into account in their development and design. These include (i) the type of phenomena annotated (either morphosyntactic, syntactic, semantic, etc.); (ii) how these phenomena are annotated (e.g., the particular guidelines and/or schema used to encode the annotations); and (iii) the languages (Java, C++, etc.) and technologies (as standalone programs, as APIs, as web services, etc.) used to develop them. This low level of interoperability makes it difficult to reuse both the linguistic annotation tools and their annotations in new scenarios, e.g., in natural language processing (NLP) pipelines. In spite of this, developing new linguistic tools from scratch is quite a high time-consuming task that also entails a very high cost. Therefore, cost-effective ways to systematically reuse linguistic tools and annotations must be found urgently. A traditional way to overcome reuse and/or interoperability problems is standardisation. In this paper, we present a web service version of FreeLing that provides standard-compliant morpho-syntactic and syntactic annotations for Spanish, according to several ISO linguistic annotation standards and standard drafts.