FileReader: error event

Note: This feature is available in Web Workers.

The error event of the FileReader interface is fired when the read failed due to an error (for example, because the file was not found or not readable).

This event is not cancelable and does not bubble.


Use the event name in methods like addEventListener(), or set an event handler property.

addEventListener("error", (event) => {});

onerror = (event) => {};

Event type

Event properties

Also inherits properties from its parent Event.

ProgressEvent.lengthComputable Read only

A boolean flag indicating if the total work to be done, and the amount of work already done, by the underlying process is calculable. In other words, it tells if the progress is measurable or not.

ProgressEvent.loaded Read only

A 64-bit unsigned integer value indicating the amount of work already performed by the underlying process. The ratio of work done can be calculated by dividing total by the value of this property. When downloading a resource using HTTP, this only counts the body of the HTTP message, and doesn't include headers and other overhead. Read only

A 64-bit unsigned integer representing the total amount of work that the underlying process is in the progress of performing. When downloading a resource using HTTP, this is the Content-Length (the size of the body of the message), and doesn't include the headers and other overhead.


const fileInput = document.querySelector('input[type="file"]');
const reader = new FileReader();

function handleSelected(e) {
  const selectedFile = fileInput.files[0];
  if (selectedFile) {
    reader.addEventListener("error", () => {
      console.error(`Error occurred reading file: ${}`);

    reader.addEventListener("load", () => {
      console.log(`File: ${} read successfully`);


fileInput.addEventListener("change", handleSelected);


File API
# dfn-error-event
File API
# dfn-onerror

Browser compatibility

BCD tables only load in the browser

See also