files/en-us/web/api/file/lastmodifieddate/index.md
{{APIRef("File API")}}{{AvailableInWorkers}}{{Deprecated_Header}}{{Non-standard_Header}}
The lastModifiedDate read-only property of the {{domxref("File")}} interface returns the last modified date of the file. Files without a known last modified date return the current date.
A {{JSXRef("Global_Objects/Date", "Date")}} object indicating the date and time at which the file was last modified.
// fileInput is a HTMLInputElement: <input type="file" multiple id="my-file-input">
const fileInput = document.getElementById("my-file-input");
for (const file of fileInput.files) {
console.log(
`${file.name} has a last modified date of ${file.lastModifiedDate}`,
);
}
To offer protection against timing attacks and fingerprinting, the precision of someFile.lastModifiedDate might get rounded depending on browser settings. In Firefox, the privacy.reduceTimerPrecision preference is enabled by default and defaults to 2ms. You can also enable privacy.resistFingerprinting, in which case the precision will be 100ms or the value of privacy.resistFingerprinting.reduceTimerPrecision.microseconds, whichever is larger.
For example, with reduced time precision, the result of someFile.lastModifiedDate.getTime() will always be a multiple of 2, or a multiple of 100 (or privacy.resistFingerprinting.reduceTimerPrecision.microseconds) with privacy.resistFingerprinting enabled.
// reduced time precision (2ms) in Firefox 60
someFile.lastModifiedDate.getTime();
// Might be:
// 1519211809934
// 1519211810362
// 1519211811670
// …
// reduced time precision with `privacy.resistFingerprinting` enabled
someFile.lastModifiedDate.getTime();
// Might be:
// 1519129853500
// 1519129858900
// 1519129864400
// …
Though present in early draft of the File API spec, this property has been removed from it and is now non-standard. Use {{domxref("File.lastModified")}} instead.
{{Compat}}