Filtering nested REST response _fields in WP 5.3

WordPress 4.9.8 introduced the ability to limit the fields included in the JSONJSON JSON, or JavaScript Object Notation, is a minimal, readable format for structuring data. It is used primarily to transmit data between a server and web application, as an alternative to XML. objects returned from the REST APIREST API The REST API is an acronym for the RESTful Application Program Interface (API) that uses HTTP requests to GET, PUT, POST and DELETE data. It is how the front end of an application (think “phone app” or “website”) can communicate with the data store (think “database” or “file system”), for example specifying


to return a list of posts with only id, title & author fields in situations where we don’t need all of the data contained in other fields like content or media (see #38131). Since 4.9.8 we’ve made further improvements to skip computing fields we did not explicitly request when _fields is present, saving time on the server in addition to slimming down the JSON response object.

In WordPress 5.3 we are adding the ability to filterFilter Filters are one of the two types of Hooks They provide a way for functions to modify data of other functions. They are the counterpart to Actions. Unlike Actions, filters are meant to work in an isolated manner, and should never have side effects such as affecting global variables and output. by nested fields. Previously we could only request top-level properties like content or meta, which would return the full content object (with raw and rendered properties when using an edit context) or the object containing all metaMeta Meta is a term that refers to the inside workings of a group. For us, this is the team that works on internal WordPress sites like WordCamp Central and Make WordPress. values. We can now specify a nested path such as content.raw and the REST API will skip computing the rendered content, a useful performance boost for applications like GutenbergGutenberg The Gutenberg project is the new Editor Interface for WordPress. The editor improves the process and experience of creating new content, making writing rich content much simpler. It uses ‘blocks’ to add richness rather than shortcodes, custom HTML etc. which only require that underlying raw post content.

Now that we can register complex array or object meta, we may similarly ask for only a few of many registered meta fields, or certain properties within a complex object, using a query such as this:


(Note that this specific meta example depends on bugfix #48266, which will ship as part of RC1.)

Thank you @timothyblynjacobs, @dlh, @danielbachhuber, and @rmccue for assisting with the development of this useful feature!

#5-3, #dev-notes, #rest-api