Instead of ‘login’ and ‘password’ use your credentials from https://app.dataforseo.com/api-access

# Instead of 'login' and 'password' use your credentials from https://app.dataforseo.com/api-access \
login="login" 
password="password" 
cred="$(printf ${login}:${password} | base64)" 
curl --location --request POST "https://api.dataforseo.com/v3/on_page/task_post" \
--header "Authorization: Basic ${cred}"  \
--header "Content-Type: application/json" \
--data-raw '[
  {
    "target": "dataforseo.com",
    "max_crawl_pages": 10,
    "load_resources": true,
    "enable_javascript": true,
    "custom_js": "meta = {}; meta.url = document.URL; meta;",
    "tag": "some_string_123",
    "pingback_url": "https://your-server.com/pingscript?id=$id&tag=$tag"
  }
]'

<?php
// You can download this file from here https://cdn.dataforseo.com/v3/examples/php/php_RestClient.zip
require('RestClient.php');
$api_url = 'https://api.dataforseo.com/';
// Instead of 'login' and 'password' use your credentials from https://app.dataforseo.com/api-access
$client = new RestClient($api_url, null, 'login', 'password');

$post_array = array();
// example #1 - a simple way to set a task
$post_array[] = array(
   "target" => "dataforseo.com",
   "max_crawl_pages" => 10
);
// example #2 - a way to set a task with additional parameters
$post_array[] = array(
   "target" => "dataforseo.com",
   "max_crawl_pages" => 10,
   "load_resources" => true,
   "enable_javascript" => true,
   "custom_js" => "meta = {}; meta.url = document.URL; meta;",
   "tag" => "some_string_123",
   "pingback_url" => 'https://your-server.com/pingscript?id=$id&tag=$tag'
);

// this example has a 2 elements, but in the case of large number of tasks - send up to 100 elements per POST request
if (count($post_array) > 0) {
   try {
      // POST /v3/on_page/task_post
      // the full list of possible parameters is available in documentation
      $result = $client->post('/v3/on_page/task_post', $post_array);
      print_r($result);
      // do something with post result
   } catch (RestClientException $e) {
      echo "\n";
      print "HTTP code: {$e->getHttpCode()}\n";
      print "Error code: {$e->getCode()}\n";
      print "Message: {$e->getMessage()}\n";
      print  $e->getTraceAsString();
      echo "\n";
   }
}
$client = null;
?>

from random import Random
from client import RestClient
# You can download this file from here https://api.dataforseo.com/v3/_examples/python/_python_Client.zip
client = RestClient("login", "password")

rnd = Random()
post_data = dict()
# example #1 - a simple way to set a task
post_data[rnd.randint(1, 30000000)] = dict(
    target="dataforseo.com",
    max_crawl_pages=10
)
# example #2 - a way to set a task with additional parameters
post_data[rnd.randint(1, 30000000)] = dict(
    target="dataforseo.com",
    max_crawl_pages=10,
    load_resources=True,
    enable_javascript=True,
    custom_js="meta = {}; meta.url = document.URL; meta;",
    tag="some_string_123",
    pingback_url="https://your-server.com/pingscript?id=$id&tag=$tag"
)
# POST /v3/on_page/task_post
# the full list of possible parameters is available in documentation
response = client.post("/v3/on_page/task_post", post_data)
# you can find the full list of the response codes here https://docs.dataforseo.com/v3/appendix/errors
if response["status_code"] == 20000:
    print(response)
    # do something with result
else:
    print("error. Code: %d Message: %s" % (response["status_code"], response["status_message"]))

const post_array = [];

post_array.push({
  "target": "dataforseo.com",
  "max_crawl_pages": 10,
  "load_resources": true,
  "enable_javascript": true,
  "custom_js": "meta = {}; meta.url = document.URL; meta;",
  "tag": "some_string_123",
  "pingback_url": "https://your-server.com/pingscript?id=$id&tag=$tag"
});

const axios = require('axios');

axios({
  method: 'post',
  url: 'https://api.dataforseo.com/v3/on_page/task_post',
  auth: {
    username: 'login',
    password: 'password'
  },
  data: post_array,
  headers: {
    'content-type': 'application/json'
  }
}).then(function (response) {
  var result = response['data']['tasks'];
  // Result data
  console.log(result);
}).catch(function (error) {
  console.log(error);
});

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading.Tasks;

namespace DataForSeoDemos
{
    public static partial class Demos
    {
        public static async Task on_page_task_post()
        {
            var httpClient = new HttpClient
            {
                BaseAddress = new Uri("https://api.dataforseo.com/"),
                // Instead of 'login' and 'password' use your credentials from https://app.dataforseo.com/api-access
                DefaultRequestHeaders = { Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(Encoding.ASCII.GetBytes("login:password"))) }
            };
            var postData = new List<object>();
            // example #1 - a simple way to set a task
            postData.Add(new
            {
                target = "dataforseo.com",
                max_crawl_pages = 10
            });
            // example #2 - a way to set a task with additional parameters
            postData.Add(new
            {
                target = "dataforseo.com",
                max_crawl_pages = 10,
                load_resources = true,
                enable_javascript = true,
                custom_js = "meta = {}; meta.url = document.URL; meta;",
                tag = "some_string_123",
                pingback_url = "https://your-server.com/pingscript?id=$id&tag=$tag"
            });
            // POST /v3/on_page/task_post
            // the full list of possible parameters is available in documentation
            var taskPostResponse = await httpClient.PostAsync("/v3/on_page/task_post", new StringContent(JsonConvert.SerializeObject(postData)));
            var result = JsonConvert.DeserializeObject<dynamic>(await taskPostResponse.Content.ReadAsStringAsync());
            // you can find the full list of the response codes here https://docs.dataforseo.com/v3/appendix/errors
            if (result.status_code == 20000)
            {
                // do something with result
                Console.WriteLine(result);
            }
            else
                Console.WriteLine($"error. Code: {result.status_code} Message: {result.status_message}");
        }
    }
}

The above command returns JSON structured like this:

{
  "version": "0.1.20200805",
  "status_code": 20000,
  "status_message": "Ok.",
  "time": "0.0815 sec.",
  "cost": 0.00125,
  "tasks_count": 1,
  "tasks_error": 0,
  "tasks": [
    {
      "id": "08071719-1535-0216-0000-3aabdf68a6ef",
      "status_code": 20100,
      "status_message": "Task Created.",
      "time": "0.0044 sec.",
      "cost": 0.00125,
      "result_count": 0,
      "path": [
        "v3",
        "on_page",
        "task_post"
      ],
      "data": {
        "api": "on_page",
        "function": "task_post",
        "target": "dataforseo.com",
        "max_crawl_pages": 10
      },
      "result": null
    }
  ]
}