Blob: type property

The type property of a Blob object returns the MIME type of the file.

Value

A string containing the file's MIME type, or an empty string if the type could not be determined.

Examples

This example asks the user to select a number of files, then checks each file to make sure it's one of a given set of image file types.

HTML

html

<input type="file" id="input" multiple />
<output id="output">Choose image files…</output>

output {
  display: block;
  margin-top: 16px;
}

JavaScript

// Our application only allows GIF, PNG, and JPEG images
const allowedFileTypes = ["image/png", "image/jpeg", "image/gif"];

const input = document.getElementById("input");
const output = document.getElementById("output");

input.addEventListener("change", (event) => {
  const files = event.target.files;

  if (files.length === 0) {
    output.innerText = "Choose image files…";
    return;
  }

  const allAllowed = Array.from(files).every((file) =>
    allowedFileTypes.includes(file.type)
  );
  output.innerText = allAllowed
    ? "All files clear!"
    : "Please choose image files only.";
});

Result

Specifications

Specification
File API # dfn-type

Browser compatibility

BCD tables only load in the browser