Limiting accepted file types I believe you're referring to a user's file input popup and you want to limit it over there. For example, if your file input lets users upload a profile picture, you probably want them to select web-compatible image formats, such as JPEG or PNG.

Acceptable file types can be specified with the accept attribute, which takes a comma-separated list of allowed file extensions or MIME types. Some examples:

accept="image/png" or accept=".png" — Accepts PNG files. accept="image/png, image/jpeg" or accept=".png, .jpg, .jpeg" — Accept PNG or JPEG files. accept="image/*" — Accept any file with an image/* MIME type. (Many mobile devices also let the user take a picture with the camera when this is used.) accept=".doc,.docx,.xml,application/msword,application/vnd.openxmlformats-officedocument.wordprocessingml.document" — accept anything that smells like an MS Word document. Here's a sample code for you from Mozilla Dev Docs.

<form method="post" enctype="multipart/form-data">
  <div>
    <label for="profile_pic">Choose file to upload</label>
    <input type="file" id="profile_pic" name="profile_pic"
          accept=".jpg, .jpeg, .png">
  </div>
  <div>
    <button>Submit</button>
  </div>
</form>

Please Note You can't disable All files from the popup you can only allow certain file types to be accepted.