---
title: Versioning
slug: fourkites-api-reference/mfjs-versioning
description: Learn how FourKites implements Semantic Versioning for its APIs, ensuring smooth integration with minimal disruptions. Understand the use of the Accept header to specify the API version and discover what changes trigger a new major version. Find out which
createdAt: 2023-04-14T06:59:14.000Z
---

When backward-incompatible changes are made to the API, a new, major version is released. The current version is **v1**. FourKites® uses [Semantic Versioning](https://semver.org/) to version its APIs.

The **Accept** header provides an ability to fetch different versions of the API. If no version is specified, the latest version of the API is used.

The following items are **backward compatible and will not require the major version to be incremented**:

- Adding properties to JSON objects.
- Changing the defaults or thresholds of the number of items returned in a single listing request.
- Changing rate limiting thresholds.
- The structure or length of identifiers (FourKites® given/generated identifiers) generated by the API.
- Changing error or status code messages.

The following items are considered **backward in-compatible and will require the major version string to be incremented**:

- Removing properties from JSON objects.
- Changing an APIs URL structure.