To set the header

Accept: application/json

on an updateLoginFlow request, you need to include it in your HTTP request when submitting the login flow. This header indicates that you expect a JSON response, which is particularly useful for client-side (AJAX) browser applications or API flows. Here's an example of how to do this using cURL:

bash curl -X POST \       -H 'Content-Type: application/json'\       -H 'Accept: application/json' \       -d '{"method":"password","csrf_token":"your-csrf-token","identifier":"<mailto:email@example.com|email@example.com>","password":"verystrongpassword"}' \       -b cookies.txt \       -c cookies.txt \       "https://$<http://PROJECT_SLUG.projects.oryapis.com/self-service/login?flow=<your-flow-id|PROJECT_SLUG.projects.oryapis.com/self-service/login?flow=<your-flow-id>>"

[Kratos > Bring-your-own-ui > Integration basics > Login flow > Submit login flow](https://www.ory.sh/docs/kratos/bring-your-own-ui/custom-ui-basic-integration#submit-login-flow) By setting the

Accept: application/json

header, you're telling the server that you want a JSON response. This is particularly important for client-side applications or API flows, as it changes the behavior of the endpoint: 1. For browser flows with this header, instead of redirecting, the server will respond with: - HTTP 200 and a JSON body containing the signed-in identity and a

Set-Cookie

header on success. - HTTP 303 redirect to a fresh login flow if the original flow expired. - HTTP 400 for form validation errors. 2. For API flows, it ensures you receive a JSON response with the appropriate status codes and data. [Ory API Reference > Ory APIs - frontend > Methods > updateLoginFlow](https://www.ory.sh/docs/reference/api) Remember that when using this approach, you need to handle the JSON response appropriately in your application logic, as you won't get automatic redirects that you would in a typical browser flow without this header.

To set the

Accept: application/json

header when using the

@ory/client

in JavaScript or TypeScript, you would typically initialize your client with a configuration object. However, the

@ory/client

package automatically sets the

Accept: application/json

header for you, so you don't need to set it manually. Here's an example of how you might initialize the client:

javascript import { Configuration, FrontendApi } from '@ory/client'  const kratos = new FrontendApi(   new Configuration({ basePath: '<https://playground.projects.oryapis.com/api/kratos/public>' }) )

Then, you can use the

kratos

instance to call the

initializeSelfServiceLoginFlowWithoutBrowser

method, which sends a GET request to the

/self-service/login/browser

endpoint with the

Accept: application/json

header:

javascript kratos.initializeSelfServiceLoginFlowWithoutBrowser().then(({ data: flow }) => {   // Handle the flow data here... })

This example is for initializing a login flow, but the process would be similar for updating a login flow or other operations. [Docs > Kratos > Self-service flows > API flows: Native Mobile & Desktop Apps, Command Line Interfaces, Smart TVs and more > Form rendering](https://www.ory.sh/docs/kratos/self-service#form-rendering-2) Please note that the actual methods and usage may vary depending on the specific version of the

@ory/client

package you're using and the operation you're trying to perform. Always refer to the official documentation or the package's TypeScript definitions for the most accurate information.