JSON:API Resource Relationships and Pagination

The JSON:API specification provides a standardized convention for structuring HTTP requests and responses, eliminating the friction of ad-hoc REST API design. By defining strict conventions for data serialization, the specification establishes predictable methods for expressing complex resource relationships and handling pagination. This article breaks down how JSON:API defines relationships through resource linkage and compound documents, and how it handles pagination via standardized query parameters, hypermedia controls, and metadata.

Standardizing Resource Relationships

In standard REST, developers often struggle to decide whether to nest related objects directly, return flat IDs, or build bespoke endpoints. JSON:API resolves this by defining an explicit relationships object within any primary resource object.

Relationship Objects and Resource Identifiers

Every relationship between resources is expressed using Resource Identifier Objects, which must contain at least a type and an id. This approach separates identity from attributes, ensuring clients know the exact type and identifier of related entities without inspecting payload properties.

A relationship entry typically exposes two types of links:

  • self: A URL that points directly to the relationship itself, allowing clients to update or delete the association independently of the resources.
  • related: A URL pointing to the related resource or collection of resources, allowing direct retrieval of the related data.

Compound Documents and Sideloading

To solve the common "N+1 query" network overhead problem, JSON:API introduces compound documents using the include query parameter. A client can request a primary resource and its related entities in a single HTTP request (e.g., GET /articles/1?include=author,comments).

Instead of deeply nesting related data inside the primary resource, JSON:API places all related items into a top-level included array. Each entity inside included is a normalized resource object with its own type, id, attributes, and relationships. This structure prevents data duplication, enables efficient client-side caching, and allows clients to reconstruct object graphs deterministically.

Standardizing Pagination

REST architectures frequently suffer from fragmented pagination schemes, alternating arbitrarily between offset/limit, page/per_page, or cursor tokens across different services. JSON:API unifies pagination mechanisms while remaining flexible enough to support diverse backend databases.

The page Query Parameter Family

JSON:API reserves the page query parameter exclusively for pagination. While the specification does not mandate a single pagination algorithm, it standardizes the parameter naming namespace using brackets:

  • Page-based: page[number]=2&page[size]=20
  • Offset-based: page[offset]=40&page[limit]=20
  • Cursor-based: page[after]=cursor_token&page[size]=25

By constraining pagination keys to the page[...] format, JSON:API guarantees that pagination parameters do not collide with filtering (filter[...]) or sorting (sort) logic.

JSON:API emphasizes HATEOAS (Hypermedia as the Engine of Application State) by utilizing the top-level links object to guide client pagination. Rather than forcing clients to manually compute URL strings for next or previous pages, servers return ready-to-use pagination links:

  • first: The URL to the first page of data.
  • prev: The URL to the previous page of data (omitted on the first page).
  • next: The URL to the next page of data (omitted on the final page).
  • last: The URL to the final page of data (often omitted in cursor-based pagination).

Clients can traverse large collections simply by following the provided URLs, decoupling client-side code from the server's underlying pagination mechanics.

Pagination Metadata

When additional context is required—such as total records or page counts—JSON:API directs this information to the top-level meta object. Because standard resource attributes and hypermedia links are strictly separated, metadata such as total-records or total-pages can be delivered without polluting the core data payload.