Laravel 5.5 ajax call 419 (unknown status)

Use this in the head section:

<meta name="csrf-token" content="{{ csrf_token() }}">

and get the csrf token in ajax:

$.ajaxSetup({
  headers: {
    'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content')
  }
});

Please refer Laravel Documentation csrf_token

Another way to resolve this is to use the _token field in ajax data and set the value of {{csrf_token()}} in blade. Here is a working code that I just tried at my end.

$.ajax({
    type: "POST",
    url: '/your_url',
    data: { somefield: "Some field value", _token: '{{csrf_token()}}' },
    success: function (data) {
       console.log(data);
    },
    error: function (data, textStatus, errorThrown) {
        console.log(data);

    },
});

This is similar to Kannan's answer. However, this fixes an issue where the token should not be sent to cross-domain sites. This will only set the header if it is a local request.

HTML:

<meta name="csrf-token" content="{{ csrf_token() }}">

JS:

$.ajaxSetup({
    beforeSend: function(xhr, type) {
        if (!type.crossDomain) {
            xhr.setRequestHeader('X-CSRF-Token', $('meta[name="csrf-token"]').attr('content'));
        }
    },
});

It's possible your session domain does not match your app URL and/or the host being used to access the application.

1.) Check your .env file:

SESSION_DOMAIN=example.com
APP_URL=example.com

2.) Check config/session.php

Verify values to make sure they are correct.