Fusio is an open source API management platform which helps to build and manage RESTful APIs. We think that there is a huge potential in the API economy. Whether you need an API to expose your business functionality, build micro services, develop SPAs or Mobile-Apps. Because of this we think that Fusio is a great tool to simplify building such APIs. More information on https://www.fusio-project.org/


The originally idea of Fusio was to provide a tool which lets you easily build a great API beside an existing application. I.e. in case you have already a web application on a domain acme.com Fusio helps you to build the fitting API at api.acme.com. Beside this use case you can also use Fusio to build a new API from scratch or use it internally i.e. for micro services.

To build the API Fusio can connect to many different databases, message queue systems or internal web services. There are also many ways to integrate your business logic into the API of Fusio.


Fusio covers all important aspects of the API lifecycle so you can concentrate on building the actual business logic of your API.

  • Versioning

    It is possible to define different versions of your endpoint. A concrete version can be requested through the Accept header i.e. application/vnd.acme.v1+json

  • Documentation

    Fusio generates automatically a documentation of the API endpoints based on the provided schema definitions.

  • Validation

    Fusio uses the standard JSONSchema to validate incoming request data.

  • Authorization

    Fusio uses OAuth2 for API authorization. Each app can be limited to scopes to request only specific endpoints of the API.

  • Analytics

    Fusio monitors all API activities and shows them on a dashboard so you always know what is happening with your API.

  • Rate limiting

    It is possible to limit the requests to a specific threshold.

  • Specifications

    Fusio generates different specification formats for the defined API endpoints i.e. OpenAPI, Swagger, RAML.

  • Subscription

    Fusio contains a subscription layer which helps to build pub/sub for your API.

  • User management

    Fusio provides an API where new users can login or register a new account through GitHub, Google, Facebook or through normal email registration.

  • Logging

    All errors which occur in your endpoint are logged and are visible at the backend including all information from the request.

  • Connection

    Fusio provides an adapter system to connect to external services. By default we provide the HTTP and SQL connection type but there are many other types available i.e. MongoDB, Amqp, Cassandra.

  • Migration

    Fusio has a migration system which allows you to change the database schema on deployment.

  • Testing

    Fusio provides an api test case wherewith you can test every endpoint response without setting up a local web server.

Basically with Fusio you only have to define the schema (request/response) of your API endpoints and implement the business logic. All other aspects are covered by Fusio.


The basic building block of Fusio is the concept of an action. An action is simply a PHP class which receives a request and returns a response. Around this action Fusio handles all common logic like Authentication, Rate-Limiting, Schema validation, Logging etc. The class has to implement the following signature:


namespace App;

use Fusio\Engine\ActionAbstract;
use Fusio\Engine\ContextInterface;
use Fusio\Engine\ParametersInterface;
use Fusio\Engine\RequestInterface;

class HelloWorld extends ActionAbstract
    public function handle(RequestInterface $request, ParametersInterface $configuration, ContextInterface $context)
        return $this->response->build(200, [], [
            'hello' => 'world',

To give you a first overview, every request which arrives at such an action goes through the following lifecycle:


Fusio tries to assign the incoming request to a fitting route. The route contains all schema information about the incoming request and outgoing responses. Those schemas are also used at the documentation which is automatically available. If a request schema was provided the incoming request body gets validated after this schema. In case everything is ok the action which is assigned to the route gets executed.

An action represents the code which handles an incoming request and produces a response. Each action can use connections to accomplish this task. A connection uses a library which helps to work with a remote service. I.e. the SQL connection uses the Doctrine DBAL library to work with a database (it returns a Doctrine\DBAL\Connection instance). A connection always returns a fully configured object so you never have to deal with any credentials in an action. There are already many different actions available which you can use i.e. to create an API based on a database table.

With Fusio we want to remove as many layers as possible so that you can work in your action directly with a specific library. Because of this Fusio has no model or entity system like many other frameworks, instead we recommend to write plain SQL in case you work with a relational database. We think that building API endpoints based on models/entities limits the way how you would design a response. You only need to describe the request and response in the JSON schema format. This schema is then the contract of your API endpoint, how you produce this response technically is secondary. Fusio provides the mentioned connections, which help you to create complete customized responses based on complicated SQL queries, message queue inserts or multiple remote HTTP calls.


Fusio provides two ways to develop an API. The first way is to build API endpoints only through the backend interface by using all available actions. Through this you can solve already many tasks especially through the usage of the PHP-Sandbox or V8-Processor action.

The other way is to use the deploy mechanism. Through this you can use normal PHP files to implement your business logic and thus you can use the complete PHP ecosystem. Therefor you need to define a .fusio.yml deploy file which specifies the available routes and actions of the system. This file can be deployed with the following command:

php bin/fusio deploy

The action of each route contains the source which handles the business logic. This can be i.e. a php class, a simple php file or a url. More information in the src/ folder. In the following an example action to build an API response from a database:


namespace App\Todo;

use Fusio\Engine\ActionAbstract;
use Fusio\Engine\ContextInterface;
use Fusio\Engine\ParametersInterface;
use Fusio\Engine\RequestInterface;

class Collection extends ActionAbstract
    public function handle(RequestInterface $request, ParametersInterface $configuration, ContextInterface $context)
        /** @var \Doctrine\DBAL\Connection $connection */
        $connection = $this->connector->getConnection('System');

        $count   = $connection->fetchColumn('SELECT COUNT(*) FROM app_todo');
        $entries = $connection->fetchAll('SELECT * FROM app_todo WHERE status = 1 ORDER BY insertDate DESC LIMIT 16');

        return $this->response->build(200, [], [
            'totalResults' => $count,
            'entry' => $entries,

In the code we get the System connection which returns a \Doctrine\DBAL\Connection instance but we have already many adapters to connect to different services. Then we simply fire some queries and return the response.


Fusio provides several apps which work with the internal backend API. These apps can be used to manage and work with the API. This section gives a high level overview what the Fusio system provides and how the application is structured. Lets take a look at the components which are provided by Fusio:



If you install a Fusio system it setups the default API. Through the API it is possible to manage the complete system. Because of that Fusio has some reserved paths which are needed by the system.

  • /backend

    Endpoints for the system configuration

  • /consumer

    Endpoints for the consumer i.e. register new accounts or create new apps

  • /doc

    Endpoints for the documentation

  • /authorization

    Endpoints for the consumer to get i.e. information about the user itself and to revoke an obtained access token

  • /export

    Endpoints to export the documentation into other formats i.e. swagger

There is also a complete documentation about all internal API endpoints.


The following apps are working with the Fusio API.



The backend app is the app where the administrator can configure the system. The app is located at /fusio/.


Fusio has a marketplace which contains a variety of apps for specific use cases. Every app can be directly installed from the backend app under System / Marketplace.

Use cases

Today there are many use cases where you need a great documented REST API. In the following we list the most popular choices where Fusio comes in to play.

Business functionality

Exposing an API of your business functionality is a great way to extend your product. You enable customers to integrate it into other applications which gives the possibility to open up for new markets. With Fusio you can build such APIs and integrate them seamlessly into your product. We also see many companies which use the API itself as the core product.

Micro services

With Fusio you can simply build small micro services which solve a specific task in a complex system.

Javascript applications

Javascript frameworks like i.e. AngularJS or EmberJS becoming the standard. With Fusio you can easily build a backend for such applications. So you dont have to build the backend part by yourself.

Mobile apps

Almost all mobile apps need some form to interact with a remote service. This is mostly done through REST APIs. With Fusio you can easily build such APIs which then can also be used by other applications.