Get an update on console as soon as a slot opens up in https://selfregistration.cowin.gov.in/ . Login to the website and then run this script on Console.

cowin_schedule_district_wise.js

// This script will alert you whenever some slot opens up on the given date within the given District IDs
// Change the districts to your needs as per your city
// Change the dateArr to add your convinent set of dates

// For further update do checkout http://twitter.com/debarko/

// How To setup Video -> https://www.youtube.com/watch?v=3_N5FFegtI4

// Steps to use
// 1. Update Config
// 2. Login to https://selfregistration.cowin.gov.in/
// 3. Rigt Click on the website
// 4. Click on Inspect
// 5. Open the Console Tab on your Inspect window
// 6. Copy paste the contents of this entire file - cowin_schedule_v2.js
// 7. Press Enter
// It will run every 10 seconds and check for availability of slots.

// Config
// ------
var districts = [265, 276, 294, 277, 290, 266, 288, 292];
var dateArr = ["30-05-2021", "31-05-2021", "01-06-2021"];
var trialCounter = 1;

const sleepNow = (delay) => new Promise((resolve) => setTimeout(resolve, delay))

function httpGet(theUrl)
{
    var xmlHttp = new XMLHttpRequest();
    xmlHttp.open( "GET", theUrl, false ); // false for synchronous request
    xmlHttp.send( null );
    return xmlHttp.responseText;
}

async function fetchByDistrict() {
  console.log("Check: ", trialCounter++);
  
  for (i=0;i < districts.length; i++) {
    for (j=0; j < dateArr.length; j++) {
      url = "https://cdn-api.co-vin.in/api/v2/appointment/sessions/calendarByDistrict?district_id="+districts[i]+"&date="+dateArr[j];
      await sleepNow(1100);
      a = httpGet(url);
      try {
        a = JSON.parse(a)
      } catch(e) {
        continue;
      }
      for (c in a.centers) {
      for (s in a.centers[c].sessions) {
            if (a.centers[c].sessions[s].min_age_limit < 45 && a.centers[c].sessions[s].available_capacity > 0) {
              console.log("Trying Booking for", a.centers[c].pincode, a.centers[c].name, a.centers[c].sessions[s].available_capacity);
              var audio = new Audio('https://media.geeksforgeeks.org/wp-content/uploads/20190531135120/beep.mp3');
              audio.play();
            }
        }
      }
    }
  }
  await sleepNow(30000);
  fetchByDistrict();
}

console.log('Script Initialising');
fetchByDistrict();

cowin_schedule_v3.js

// This script will alert you whenever some slot opens up on the given date within the given pincodes
// Change the pincodes to your needs as per your city
// Change the dateArr to add your convinent set of dates

// For further update do checkout http://twitter.com/debarko/

// How To setup Video -> https://www.youtube.com/watch?v=3_N5FFegtI4

// Steps to use
// 1. Update Config
// 2. Login to https://selfregistration.cowin.gov.in/
// 3. Rigt Click on the website
// 4. Click on Inspect
// 5. Open the Console Tab on your Inspect window
// 6. Copy paste the contents of this entire file - cowin_schedule_v2.js
// 7. Press Enter
// It will run every 10 seconds and check for availability of slots.

// Config
// ------

var pincodes = ["560076", "560020", "560078", "560001", "560017", "560103", "560027", "560064", "560071", "560084", "560035", "560066", "560048"];
var dateArr = ["30-05-2021", "31-05-2021", "01-06-2021"];
var trialCounter = 1;

const sleepNow = (delay) => new Promise((resolve) => setTimeout(resolve, delay))

function httpGet(theUrl)
{
    var xmlHttp = new XMLHttpRequest();
    xmlHttp.open( "GET", theUrl, false ); // false for synchronous request
    xmlHttp.send( null );
    return xmlHttp.responseText;
}

async function fetchByPincode() {
    console.log("Check: ", trialCounter++);
    
    for (i=0;i < pincodes.length; i++) {
      for (j=0; j < dateArr.length; j++) {
        url = "https://cdn-api.co-vin.in/api/v2/appointment/sessions/calendarByPin?pincode="+pincodes[i]+"&date="+dateArr[j];
        await sleepNow(1100);
        a = httpGet(url);
        try {
          a = JSON.parse(a)
        } catch(e) {
          continue;
        }
        for (c in a.centers) {
        for (s in a.centers[c].sessions) {
              if (a.centers[c].sessions[s].min_age_limit < 45 && a.centers[c].sessions[s].available_capacity > 0) {
                console.log("Trying Booking for", a.centers[c].pincode, a.centers[c].name, a.centers[c].sessions[s].available_capacity);
                var audio = new Audio('https://media.geeksforgeeks.org/wp-content/uploads/20190531135120/beep.mp3');
                audio.play();
              }
          }
        }
      }
    }
    await sleepNow(30000);
    fetchByPincode();
}

console.log('Script Initialising');
fetchByPincode();

I have create 100% working and faster script to get CoWin vaccine slot availability alerts.

Cowin Vaccine Alert Script

Please Check...

Thank varun,It is working as nicely.I took the vaccine today
Only we could have use pincode ,it would be more user friendlier