Blob: size property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

Note: This feature is available in Web Workers.

The size read-only property of the Blob interface returns the size of the Blob or File in bytes.

Value

The number of bytes of data contained within the Blob (or Blob-based object, such as a File).

Examples

This example uses an <input> element of type file to ask the user for a group of files, then iterates over those files outputting their names and lengths in bytes.

HTML

html

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

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

JavaScript

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

input.addEventListener("change", (event) => {
  output.innerText = "";

  for (const file of event.target.files) {
    output.innerText += `${file.name} has a size of ${file.size} bytes.\n`;
  }
});

Result

Specifications

Specification
File API # dfn-size

Browser compatibility

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