The File.lastModified read-only property provides the last modified date of the file as the number of milliseconds since the Unix epoch (January 1, 1970 at midnight). Files without a known last modified date return the current date.


const time = instanceOfFile.lastModified;


A number that represents the number of milliseconds since the Unix epoch.


Reading from file input

<input type="file" multiple id="fileInput">
const fileInput = document.querySelector('#fileInput');
fileInput.addEventListener('change', (event) => {
  // files is a FileList object (similar to NodeList)
  const files =;

  for (let file of files) {
    const date = new Date(file.lastModified);
    console.log(`${} has a last modified date of ${date}`);

Try the results out below:

Dynamically created files

If a File is created dynamically, the last modified time can be supplied in the new File() constructor function. If it is missing, lastModified inherits the current time from at the moment the File object gets created.

const fileWithDate = new File([], 'file.bin', {
  lastModified: new Date(2017, 1, 1),
console.log(fileWithDate.lastModified); //returns 1485903600000

const fileWithoutDate = new File([], 'file.bin');
console.log(fileWithoutDate.lastModified); //returns current time

Reduced time precision

To offer protection against timing attacks and fingerprinting, the precision of someFile.lastModified might get rounded depending on browser settings.
In Firefox, the privacy.reduceTimerPrecision preference is enabled by default and defaults to 20us in Firefox 59; in 60 it will be 2ms.

// reduced time precision (2ms) in Firefox 60
// 1519211809934
// 1519211810362
// 1519211811670
// ...

// reduced time precision with `privacy.resistFingerprinting` enabled
// 1519129853500
// 1519129858900
// 1519129864400
// ...

In Firefox, you can also enabled privacy.resistFingerprinting, the precision will be 100ms or the value of privacy.resistFingerprinting.reduceTimerPrecision.microseconds, whichever is larger.


Specification Status Comment
File API
The definition of 'lastModified' in that specification.
Working Draft Initial definition.

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
lastModifiedChrome Full support 13Edge Full support 18Firefox Full support 15IE No support NoOpera Full support 16Safari Full support 10WebView Android Full support YesChrome Android Full support YesFirefox Android No support NoOpera Android No support NoSafari iOS Full support 10Samsung Internet Android Full support Yes


Full support
Full support
No support
No support

See also