# What has changed in Jitsu 2.0

## Event format

Jitsu 2.0 uses the Segment-compatible [events specifications](https://segment.com/docs/connections/spec/) instead of the custom format in Jitsu Classic.

:::info
When Jitsu Classic compatibility endpoints are used with Jitsu 2.0 incoming events are automatically transformed into the new format.
However, additional adjustments may be needed to ensure all data is processed in the same way as it was in Jitsu Classic.

Check the [Step by Step Guide](/docs/migration-from-classic/step-by-step) for more details.

:::

## New APIs and Client Library

Jitsu 2.0 introduces new APIs for events [ingestion](/docs/sending-data/http) while maintaining backward compatibility with Jitsu Classic at the endpoint level.

With the new APIs, Jitsu 2.0 provides a [new client library](/docs/sending-data/npm).

Jitsu 2.0 implements the Segment-compatible HTTP API [Batch endpoint](/docs/sending-data/http#batch-endpoint). That allows to use the most of Segment client libraries with Jitsu 2.0.

:::info

Jitsu 2.0 maintains backward compatibility with Jitsu Classic at the events endpoint level.  This means that migrating to Jitsu 2.0 requires minimal changes on the client side — specifically, updating the Jitsu host and write key. See the [Client Configuration](/docs/migration-from-classic/step-by-step#change-client-configuration) section.

:::

## Project Layout

In Jitsu Classic, the event processing pipeline is configured through a link: **API Key** → **Destination** or **Source** → **Destination**.

Jitsu 2.0 introduces a redesigned project layout that is more modular and flexible.:

* **API Key** entity is replaced by the **Site** entity.
* **Source** entity is replaced by **Service Connector**
* **Destination** is split into  **Destination**, **Connection**, **Function**, **Sync** entities:
  * New **Destination** entity only sets credentials and destination-specific settings.
  * **Connection**: These entities link Sites to Destinations, configure the transformation pipeline, and manage all data processing settings.
  * **Function**: Dedicated entities for defining transformation and enrichment logic.
  * **Sync**: Entities that link Service Connectors to Destinations and define data import settings.

For more details see [Core Concepts](/docs/core-concepts).

## Data Warehouses Data Layout

Jitsu 2.0 uses the Segment-compatible event format. This means that the table layout in the data warehouse will be also similar to layout produced by Segment.

To make Jitsu 2.0 use the same table layout as Jitsu Classic, you need to set up a **Connection** entity with the **Data Layout** set to **Legacy Jitsu**.