W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

h1 {
  text-align: center;
  padding: 20px;
}

.gallery {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-start;
  padding: 0 15px;
}

.gallery-item {
  position: relative;
  width: calc(25% - 20px);
  height: auto;
  margin: 10px;
  cursor: pointer;
  transition: transform 0.5s ease;
}

.gallery-item:hover {
  transform: scale(1.1);
}

/* The Modal (background) */
.modal {
  display: none;
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.8);
  align-items: center;
  justify-content: center;
  transition: opacity 0.5s ease;
}

/* Modal content (image) */
.modal-content {
  position: relative;
  width: 90%;
  height: auto;
  max-width: 90%;
  max-height: 90%;
  border-radius: 5px;
  overflow: hidden;
  animation: zoomIn 0.5s;
}

@keyframes zoomIn {
  from {transform: scale(0.6);}
  to {transform: scale(1);}
}

.modal.show {
  display: flex;
  opacity: 1;
}

/* Close button */
.close {
  position: absolute;
  top: 10px;
  right: 15px;
  color: #ffffff;
  font-size: 35px;
  font-weight: bold;
  cursor: pointer;
  transition: transform 0.3s;
}

/* Caption of modal image */
.caption {
  position: absolute;
  bottom: 15px;
  width: 100%;
  text-align: center;
  color: #ffffff;
  font-size: 24px;
}

@media screen and (max-width: 768px) {
  .gallery-item {
     width: calc(50% - 20px);
  }
}

@media screen and (max-width: 480px) {
  .gallery-item  {
    width: calc(100% - 20px);
  }
}
</style>
</head>
<body>

<h1>Responsive Modal Images</h1>
    
<div class="gallery">
  <img src="img_5terre.jpg" alt="Cinque Terre" class="gallery-item" onclick="openModal('modal1', 'Cinque Terre')" width="600" height="400">
  <img src="img_forest.jpg" alt="Forest" class="gallery-item" onclick="openModal('modal2', 'Forest')" width="600" height="400">
  <img src="img_lights.jpg" alt="Northern Lights" class="gallery-item" onclick="openModal('modal3', 'Nothern Lights')" width="600" height="400">
  <img src="img_mountains.jpg" alt="Mountains" class="gallery-item" onclick="openModal('modal4', 'Mountains')" width="600" height="400">
</div>

<div id="modal1" class="modal">
  <span class="close" onclick="closeModal('modal1')">&times;</span>
  <img src="img_5terre.jpg" alt="Cinque Terre" class="modal-content" width="600" height="400">
  <div class="caption"></div>
</div>

<div id="modal2" class="modal">
  <span class="close" onclick="closeModal('modal2')">&times;</span>
  <img src="img_forest.jpg" alt="Forest" class="modal-content" width="600" height="400">
  <div class="caption"></div>
</div>

<div id="modal3" class="modal">
  <span class="close" onclick="closeModal('modal3')">&times;</span>
  <img src="img_lights.jpg" alt="Northern Lights" class="modal-content" width="600" height="400">
  <div class="caption"></div>
</div>

<div id="modal4" class="modal">
  <span class="close" onclick="closeModal('modal4')">&times;</span>
  <img src="img_mountains.jpg" alt="Mountains" class="modal-content" width="600" height="400">
  <div class="caption"></div>
</div>

function closeModal(modalId) {
  let modal = document.getElementById(modalId);
  modal.classList.remove("show");
  setTimeout(function () {
    modal.style.display = "none";
    modal.querySelector(".caption").innerText = "";
  }, 300);
}
</script>
</body>
</html>