Asset hashing uses content hash in filename

An asset named app.js with no content hash cannot be safely cached for more than a few minutes — the browser has no way to know whether the file changed since the last visit. Setting a long max-age on an unhashed asset means users receive stale code after a deploy; setting a short max-age means the asset is re-downloaded on every visit. Content hashing is the mechanism that makes aggressive 1-year caching safe: the filename itself is the cache key. ISO 25010:2011 time-behaviour links asset hashing to time-behaviour because it determines whether repeat visitors pay full download cost on every page load.

In Next.js and Vite, content hashing is automatic in production mode — verify it is not disabled in next.config.js. For custom webpack setups, configure [contenthash] in the output filename pattern.

// webpack.config.js — content hash in production
module.exports = {
  output: {
    filename: process.env.NODE_ENV === 'production'
      ? '[name].[contenthash:8].js'
      : '[name].js',
  },
}

Verify hashes are generated by inspecting .next/static/chunks/ — filenames should contain an 8-character hex string that changes when the file content changes.