How Can I Preview an Image Client-Side Before Uploading?

Preview an Image on the Client Side

To preview an image before uploading it, you can leverage HTML's file input and the URL.createObjectURL() method. Here's a detailed solution that works entirely within the browser:

In your HTML form, add an input field that allows selecting an image:

<form runat="server">
  <input accept="image/*" type='file'>

Next, create an image element to display the preview:

<img>

Finally, add JavaScript that captures the file selected in the input field and uses its content to create an object URL that is then assigned to the image element's src attribute:

imgInp.onchange = evt => {
  const [file] = imgInp.files;
  if (file) {
    blah.src = URL.createObjectURL(file);
  }
};

When a user selects an image in the input field, this code will dynamically update the image element, displaying a preview of the selected image without having to upload it to a server. This approach is convenient and efficient for presenting an instant preview of image files on the client side before the user commits to uploading them.

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