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Fingerprinting is a cache-busting technique which allows you to expire files when they actually change this is done by altering the filenames of the files. This way you can set far future expire headers without having to worry that your users might see stale or old files. Providing you with best of 2 worlds, cached assets for increased performance with sacrificing your ability to instantly modify files.


The module is released in the public npm registry and can be installed by running:

npm install --save fingerprinting


The fingerprinting module is exposed as a single function that generates the new filenames for your files. In all examples we assume that you've already required the module as followed;

'use strict';
var finger = require('fingerprinting');

The exported finger function accepts the following arguments:

  • file The path to the file or filename of the file where we're generating the file from. This is used to extract the file extension and read the file contents if no contents option is provided (please do note that reading is done using a sync fs method).
  • options Optional configuration for the fingerprint generation:
    • format: Template that specifies the format of the generated fingerprint. Defaults to {hash}.{suffix}.{ext}.
    • algorithm Hashing algorithm to be used to generate source hash. Defaults to md5.
    • map Also generate an unique id for source maps. Defaults to false.
    • env Environment that we're generating it for. It is used to generate the suffix in the filename format. For example production generates a min suffix while a mising or development generates a dev suffix. Defaults to NODE_ENV.
    • content The actual content of the filename. This eliminates the need to do a fs.readFileSync within the code. It can be either a string or Buffer.

The function returns an object with 2 keys:

  • file This is the new filename for the given file.
  • map If the map option was set to true this will contain the filename for your source map file.


var fs = require('fs');
fs.readFile(__dirname + '/index.js', function (err, buffer) {
  if (err) throw err;
  var print = finger('index.js', {
    content: buffer
  console.log('print:', print.file); //



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npm i fingerprinting

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