Error handling

Strapi is natively handling errors with a standard format.

There are 2 use cases for error handling:

• As a developer querying content through the REST or GraphQL APIs, you might receive errors in response to the requests.
• As a developer customizing the backend of your Strapi application, you could use controllers and services to throw errors.

Receiving errors

Errors are included in the response object with the error key and include information such as the HTTP status code, the name of the error, and additional information.

REST errors

Errors thrown by the REST API are included in the response that has the following format:

{
  "data": null,
  "error": {
    "status": "", // HTTP status
    "name": "", // Strapi error name ('ApplicationError' or 'ValidationError')
    "message": "", // A human readable error message
    "details": {
      // error info specific to the error type
    }
  }
}

GraphQL errors

Errors thrown by the GraphQL API are included in the response that has the following format:

{ "errors": [
    {
      "message": "", // A human reable error message
      "extensions": {
        "error": {
          "name": "", // Strapi error name ('ApplicationError' or 'ValidationError'),
          "message": "", // A human reable error message (same one as above);
          "details": {}, // Error info specific to the error type
        },
        "code": "" // GraphQL error code (ex: BAD_USER_INPUT)
      }
    }
  ],
  "data": {
    "graphQLQueryName": null
  }
}

Throwing errors

Controllers and middlewares

The recommended way to throw errors when developing any custom logic with Strapi is to have the controller or middleware respond with the correct status and body.

This can be done by calling an error function on the context (i.e. ctx). Available error functions are listed in the http-errors documentation but their name should be lower camel-cased to be used by Strapi (e.g. badRequest).

Error functions accept 2 parameters that correspond to the error.message and error.details attributes received by a developer querying the API:

• the first parameter of the function is the error message
• and the second one is the object that will be set as details in the response received

JavaScript

// path: ./src/api/[api-name]/controllers/my-controller.js

module.exports = {
  renameDog: async (ctx, next) => {
    const newName = ctx.request.body.name;
    if (!newName) {
      return ctx.badRequest('name is missing', { foo: 'bar' })
    }
    ctx.body = strapi.service('api::dog.dog').rename(newName);
  }
}

// path: ./src/api/[api-name]/middlewares/my-middleware.js

module.exports = async (ctx, next) => {
  const newName = ctx.request.body.name;
  if (!newName) {
    return ctx.badRequest('name is missing', { foo: 'bar' })
  }
  await next();
}

TypeScript

// path: ./src/api/[api-name]/controllers/my-controller.ts

export default {
  renameDog: async (ctx, next) => {
    const newName = ctx.request.body.name;
    if (!newName) {
      return ctx.badRequest('name is missing', { foo: 'bar' })
    }
    ctx.body = strapi.service('api::dog.dog').rename(newName);
  }
}

// path: ./src/api/[api-name]/middlewares/my-middleware.ts

export default async (ctx, next) => {
  const newName = ctx.request.body.name;
  if (!newName) {
    return ctx.badRequest('name is missing', { foo: 'bar' })
  }
  await next();
}

Services and models lifecycles

Once you are working at a deeper layer than the controllers or middlewares there are dedicated error classes that can be used to throw errors. These classes are extensions of Node Error class and are specifically targeted for certain use-cases.

These error classes are imported through the @strapi/utils package and can be called from several different layers. The following examples use the service layer but error classes are not just limited to services and model lifecycles. When throwing errors in the model lifecycle layer, it's recommended to use the ApplicationError class so that proper error messages are shown in the admin panel.

note

See the default error classes section for more information on the error classes provided by Strapi.

Example: Throwing an error in a service

This example shows wrapping a [core service](/dev-docs/backend-customization/services#extending-core-services) and doing a custom validation on the `create` method:

JavaScript

path: ./src/api/restaurant/services/restaurant.js

const utils = require('@strapi/utils');
const { ApplicationError } = utils.errors;
const { createCoreService } = require('@strapi/strapi').factories;

module.exports = createCoreService('api::restaurant.restaurant', ({ strapi }) =>  ({
  async create(params) {
    let okay = false;

    // Throwing an error will prevent the restaurant from being created
    if (!okay) {
      throw new ApplicationError('Something went wrong', { foo: 'bar' });
    }
  
    const result = await super.create(params);

    return result;
  }
});

TypeScript

path: ./src/api/[api-name]/policies/my-policy.ts

import utils from '@strapi/utils';
import { factories } from '@strapi/strapi';

const { ApplicationError } = utils.errors;

export default factories.createCoreService('api::restaurant.restaurant', ({ strapi }) =>  ({
  async create(params) {
    let okay = false;

    // Throwing an error will prevent the restaurant from being created
    if (!okay) {
      throw new ApplicationError('Something went wrong', { foo: 'bar' });
    }
  
    const result = await super.create(params);

    return result;
  }
}));

Example: Throwing an error in a model lifecycle

This example shows building a custom model lifecycle and being able to throw an error that stops the request and will return proper error messages to the admin panel. Generally you should only throw an error in beforeX lifecycles, not afterX lifecycles.

JavaScript

path: ./src/api/[api-name]/content-types/[api-name]/lifecycles.js

const utils = require('@strapi/utils');
const { ApplicationError } = utils.errors;

module.exports = {
  beforeCreate(event) {
    let okay = false;

    // Throwing an error will prevent the entity from being created
    if (!okay) {
      throw new ApplicationError('Something went wrong', { foo: 'bar' });
    }
  },
};

TypeScript

path: ./src/api/[api-name]/content-types/[api-name]/lifecycles.ts

import utils from '@strapi/utils';
const { ApplicationError } = utils.errors;

export default {
  beforeCreate(event) {
    let okay = false;

    // Throwing an error will prevent the entity from being created
    if (!okay) {
      throw new ApplicationError('Something went wrong', { foo: 'bar' });
    }
  },
};

Policies

Policies are a special type of middleware that are executed before a controller. They are used to check if the user is allowed to perform the action or not. If the user is not allowed to perform the action and a return false is used then a generic error will be thrown. As an alternative, you can throw a custom error message using a nested class extensions from the Strapi ForbiddenError class, ApplicationError class (see Default error classes for both classes), and finally the Node Error class.

The PolicyError class is available from @strapi/utils package and accepts 2 parameters:

• the first parameter of the function is the error message
• (optional) the second parameter is the object that will be set as details in the response received; a best practice is to set a policy key with the name of the policy that threw the error.

Example: Throwing a PolicyError in a custom policy

This example shows building a custom policy that will throw a custom error message and stop the request.

JavaScript

path: ./src/api/[api-name]/policies/my-policy.js

const utils = require('@strapi/utils');
const { PolicyError } = utils.errors;

module.exports = (policyContext, config, { strapi }) => {
  let isAllowed = false;

  if (isAllowed) {
    return true;
  } else {
    throw new PolicyError('You are not allowed to perform this action', {
      policy: 'my-policy',
      myCustomKey: 'myCustomValue',
    });
  }
}

TypeScript

path: ./src/api/[api-name]/policies/my-policy.ts

const utils = require('@strapi/utils');
const { PolicyError } = utils.errors;

export default (policyContext, config, { strapi }) => {
  let isAllowed = false;

  if (isAllowed) {
    return true;
  } else {
    throw new PolicyError('You are not allowed to perform this action', {
      policy: 'my-policy',
      myCustomKey: 'myCustomValue',
    });
  }
};

Default error classes

The default error classes are available from the @strapi/utils package and can be imported and used in your code. Any of the default error classes can be extended to create a custom error class. The custom error class can then be used in your code to throw errors.

Application

The ApplicationError class is a generic error class for application errors and is generally recommended as the default error class. This class is specifically designed to throw proper error messages that the admin panel can read and show to the user. It accepts the following parameters:

Parameter	Type	Description	Default
message	string	The error message	An application error occured
details	object	Object to define additional details	{}

throw new ApplicationError('Something went wrong', { foo: 'bar' });

Pagination

The PaginationError class is a specific error class that is typically used when parsing the pagination information from REST, GraphQL, or the Entity Service. It accepts the following parameters:

Parameter	Type	Description	Default
message	string	The error message	Invalid pagination

throw new PaginationError('Exceeded maximum pageSize limit');

NotFound

The NotFoundError class is a generic error class for throwing 404 status code errors. It accepts the following parameters:

Parameter	Type	Description	Default
message	string	The error message	Entity not found

throw new NotFoundError('These are not the droids you are looking for');

Forbidden

The ForbiddenError class is a specific error class used when a user either doesn't provide any or the correct authentication credentials. It accepts the following parameters:

Parameter	Type	Description	Default
message	string	The error message	Forbidden access

throw new ForbiddenError('Ah ah ah, you didn\'t say the magic word');

Unauthorized

The UnauthorizedError class is a specific error class used when a user doesn't have the proper role or permissions to perform a specific action, but has properly authenticated. It accepts the following parameters:

Parameter	Type	Description	Default
message	string	The error message	Unauthorized

throw new UnauthorizedError('You shall not pass!');

PayloadTooLarge

The PayloadTooLargeError class is a specific error class used when the incoming request body or attached files exceed the limits of the server. It accepts the following parameters:

Parameter	Type	Description	Default
message	string	The error message	Entity too large

throw new PayloadTooLargeError('Uh oh, the file too big!');

Policy

The PolicyError class is a specific error designed to be used with route policies. The best practice recommendation is to ensure the name of the policy is passed in the details parameter. It accepts the following parameters:

Parameter	Type	Description	Default
message	string	The error message	Policy Failed
details	object	Object to define additional details	{}

throw new PolicyError('Something went wrong', { policy: 'my-policy' });