cache-pulse

cache-pulse

Check that your static hosting config caches the right things: fingerprinted assets for a year, HTML revalidated, and nothing stale after a deploy.

Caching is the cheapest performance win and the easiest to get backwards. Fingerprinted bundles (index-BdT9x2Qa.js) should be cached for a year with immutable; HTML and unfingerprinted files (/styles.css, /logo.png) must revalidate, or visitors keep yesterday's site. cache-pulse reads the header rules in your build output or repo (_headers, vercel.json, netlify.toml, firebase.json, serve.json), resolves the Cache-Control that applies to every file, and reports the mistakes, grouped by the header rule that causes them.

CLI, library and GitHub Action. Node.js 18+, zero runtime dependencies. Works on any static build output (Astro, Next.js output: 'export', Eleventy, Hugo, Jekyll, Docusaurus, VitePress, plain HTML) and runs offline: point it at the folder your build writes. By Louis Wright.

Features

• Fingerprinted assets: content-hashed file names and framework output folders (_next/static, _astro, _app/immutable, _nuxt, CRA static/js) need max-age=31536000, immutable; short, missing, no-cache and no-store policies are reported.
• HTML: cached without revalidation or immutable is high severity; s-maxage for the CDN with max-age=0 for browsers is accepted.
• Unfingerprinted files: immutable or a max-age over a week on /styles.css or /app.js means users do not see deploys; missing policies are noted.
• Pitfalls: Vary: *, Set-Cookie on static files (no CDN caching), Content-Encoding on images and fonts.
• Compression: when the build ships .br/.gz files, every text asset over 1.4 kB should have one, and each is decompressed and compared with the original to catch stale copies.

Scope

Performance caching and compression only. Security headers (CSP, HSTS, X-Frame-Options and friends) are deliberately out of scope; use a security-header checker for those. cache-pulse reads config files and does not request a live site.

Rules

Install and run

npx cache-pulse dist
npx cache-pulse . --include '/assets/**'
npx cache-pulse public --expect-precompressed --fail-on medium

Pages are mapped to URLs the way static hosts serve them: index.html → /, blog/index.html → /blog/, about.html → /about.html (or /about with --clean-urls). Pass --base-url with your public URL, or let it be inferred from canonical / og:url tags. Meta-refresh redirect stubs and 404.html are skipped. X-Robots-Tag and Link headers are read from Netlify/Cloudflare _headers and vercel.json.

Sample output

cache-pulse — /workspace/cache-pulse/test/fixtures/bad
5 file(s) (2 fingerprinted), 4 header rule(s)

HIGH     assets/app.3f2a9c1b.js.gz assets/app.3f2a9c1b.js.gz does not decompress to the current assets/app.3f2a9c1b.js [cache-precompressed-stale]
HIGH     vercel.json:3 HTML /index.html is cached for 86400s (public, max-age=86400) [cache-html-long]
HIGH     vercel.json:4 Fingerprinted /assets/app.3f2a9c1b.js is cached only 3600s (public, max-age=3600) (+1 more file(s) with the same rule) [cache-hashed-short]
HIGH     vercel.json:5 Unfingerprinted /styles.css is cached immutable (public, max-age=31536000, immutable) [cache-unhashed-immutable]
MEDIUM   styles.css styles.css (3 KB) has no .br or .gz sibling [cache-precompressed-missing]
MEDIUM   vercel.json:4 Vary: * on /assets/app.3f2a9c1b.js (+1 more file(s) with the same rule) [cache-vary-star]

Options

cache-pulse 1.0.0 — check caching and precompression in your static hosting config

Usage: cache-pulse [site-dir] [options]

Site
      --base-url <url>        Public URL of the site, e.g. https://example.com (default: inferred from canonical/og:url)
      --include <globs>       Only check these pages (file or URL path globs, comma-separated)
      --exclude <globs>       Skip these pages
      --clean-urls            Pages are served without .html (about.html -> /about)
Caching
      --expect-precompressed   Require .br/.gz siblings for text assets even if none exist yet

Common
  -c, --config <file>     JSON config (default: .cache-pulse.json or "cachePulse" in package.json)
  -f, --format <fmt>      text (default) | json | sarif | markdown
      --json <file>       Also write a JSON report
      --sarif <file>      Also write SARIF 2.1.0
      --markdown <file>   Also write Markdown (e.g. for a job summary)
      --fail-on <sev>     critical | high | medium | low | info | none (default: high)
      --list-rules        Print rules and default severities
      --no-fixes          Hide fix suggestions in text output
      --no-color          Disable colours
  -v, --version / -h, --help

Exit codes: 0 = passed, 1 = findings at or above --fail-on, 2 = usage, config or read error.

Configuration and allowlist

Options can live in .cache-pulse.json (or a "cachePulse" key in package.json, or --config <file>):

{
  "failOn": "medium",
  "severity": {
    "cache-hashed-short": "low"
  },
  "allowlist": [
    {
      "rule": "cache-unhashed-immutable",
      "subject": "/fonts/inter-4.0.woff2",
      "reason": "Version in the file name, never changes",
      "expires": "2027-03-31"
    }
  ],
  "maxHtmlAge": 300,
  "maxUnhashedAge": 3600,
  "hashedPaths": [
    "/fonts/*-v[0-9]*.woff2"
  ],
  "expectPrecompressed": true
}

• severity changes a rule's severity, or turns it "off".
• allowlist entries suppress matching findings. Each needs a reason and matches on any combination of rule, file, subject (globs with *) and match (a substring of the message). Add expires (YYYY-MM-DD) so the exception is time-boxed: once it lapses the finding comes back along with an allowlist-expired finding (medium). Entries that no longer match anything are reported as allowlist-unused (info).

Config can also set baseUrl, include, exclude and cleanUrls. The config file is looked up in the site directory first, then in the current directory, so .cache-pulse.json can live at your repository root. Other keys: maxHtmlAge (seconds, default 600), maxUnhashedAge (default one week), hashedPaths (globs to treat as fingerprinted), expectPrecompressed, minCompressSize, plus baseUrl, include, exclude and cleanUrls.

Output and exit codes

• --format text (default), json, sarif (SARIF 2.1.0 for GitHub code scanning) or markdown (for job summaries and PR comments). --json, --sarif and --markdown write extra report files in the same run.
• --fail-on <severity> sets the threshold (critical, high, medium, low, info, none; default high).
• Exit codes: 0 passed, 1 findings at or above --fail-on, 2 usage, config or read error.

GitHub Action

permissions:
  contents: read
  security-events: write   # only needed for the SARIF upload
jobs:
  cache-pulse:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
        with: { persist-credentials: false }
      - run: npm ci && npm run build   # produce the static site first
      - uses: MrLouisWright/cache-pulse@v1
        with:
          path: dist
          fail-on: high
          sarif: cache-pulse.sarif
      - uses: github/codeql-action/upload-sarif@v3
        if: always()
        with: { sarif_file: cache-pulse.sarif }

The action runs the bundled CLI with Node 20; it has no dependencies to install. Pin it to a commit SHA if your policy requires it.

Library

import { check, isHashed, parseCacheControl } from "cache-pulse";
isHashed("/assets/index-BdT9x2Qa.js"); // true
parseCacheControl("public, max-age=31536000, immutable").immutable; // true

Types are included.

Requirements

Node.js 18 or newer. Zero runtime dependencies.

Support

If this project is useful to you, you can support its development with a donation: Buy me a coffee. It helps keep these tools maintained, documented and free for everyone.

Credit (optional)

Free to use under MIT, no attribution required. If cache-pulse helps you, a link back is appreciated:

<a href="https://louiswright.co.uk">Built with cache-pulse by Louis Wright</a>

[![Built with cache-pulse by Louis Wright](https://img.shields.io/badge/built%20with-cache--pulse-blue)](https://louiswright.co.uk)

Licence

MIT © Louis Wright (Louis Wright)