assets: icons, manifest, social cards, 404

assets checks the files around your pages that browsers, phones and social networks look for: the favicon, the Apple touch icon, the web app manifest and its icons, the Open Graph image shown when someone shares a link, and the page served for missing URLs. These break quietly: a renamed icon or a relative og:image looks fine in the browser and only shows up as a blank tab icon or a card without a picture. It is not in the default set.

Needs

Nothing to install. It reads the build (dist/) and starts no server or browser. Set the top-level siteUrl so absolute og:image URLs on your site are checked against the build and og:url is checked against your origin.

With render.mode on, it checks the DOM a browser renders instead of the shipped HTML file.

Run it

npx vidimus assets

What it checks

Pages matched by the top-level exclude or assets.exclude are skipped; by default that is the 404 page. Each check can be turned off on its own.

Favicon (assets.favicon)

• Every <link rel="icon"> and <link rel="apple-touch-icon"> on your site that points at a local file must resolve to a file in the build: icon /favicon.svg not found (error). rel="shortcut icon" counts as icon.
• If no page has a <link rel="icon"> and there is no /favicon.ico in the build root: no favicon: add <link rel="icon"> or /favicon.ico (error).
• If no page has a <link rel="apple-touch-icon"> and there is no /apple-touch-icon.png: no <link rel="apple-touch-icon"> on any page (warning).

Web app manifest (assets.manifest)

If no page links a manifest: no <link rel="manifest"> on any page (warning). Browsers need one to install the site and to pick its name, icons and theme color. The checks below run for each manifest a page links with <link rel="manifest">, and each finding lists the pages that link it.

• The file exists (manifest /site.webmanifest not found) and parses as a JSON object (manifest /site.webmanifest is not valid JSON).
• It has a name or short_name (manifest … has no name or short_name).
• It has a non-empty icons array (manifest … has no icons), and each icon src, resolved relative to the manifest, exists in the build (manifest icon /icons/512.png not found).
• At least one icon is 512 pixels or larger on its shorter side, from its declared sizes ("any" counts) or its measured size: otherwise manifest … has no icon of at least 512x512 (warning).

Open Graph and Twitter cards (assets.openGraph)

Pages with <meta name="robots" content="noindex"> are skipped, since they are not meant to be shared.

• og:title, og:image and twitter:card are present and not empty; each missing one is a warning such as missing <meta property="og:image">. vidimus accepts the key in either the property or the name attribute.
• og:image is an absolute URL (og:image "/og.png" is not an absolute URL, error). Social networks do not resolve relative URLs.
• An og:image on your site exists in the build (og:image /og.png not found, error) and, when its size can be read (PNG, JPEG, GIF, WebP, AVIF, SVG), is at least assets.ogImage: og:image /og.png is 800x418, smaller than 1200x630 (warning).
• With siteUrl set, og:url is on the same origin: og:url origin https://staging.example.com differs from siteUrl https://example.com (error).

404 page (assets.notFound)

Without 404.html or 404/index.html in the build: no 404 page (404.html or 404/index.html) (warning). Most static hosts serve that file for missing URLs.

Files the site turns out to need

Some root files only matter for some sites: ads.txt for sites that show ads, a change-password URL for sites with accounts, app association files for sites with an app. vidimus looks for signs in the pages and checks the file only when a sign is there, so you don't need to know the file exists to be told you need it. Each option takes 'auto' (default: check when a sign is found), 'on' (always check) or 'off'. A missing file is a warning listing the pages that gave the sign away; an invalid one is an error.

• ads.txt: every record must read <domain>, <account id>, DIRECT|RESELLER[, <cert id>] (ads.txt has malformed lines, with the line numbers), and there must be at least one. An AdSense ca-pub-… ID found in a page must have its google.com, pub-… line: ads.txt does not list AdSense publisher pub-…. Advertiser pixels such as Google Ads conversion tracking don't count as ads. An app-ads.txt in the build is checked the same way; vidimus never asks for one, since no page can tell whether your app shows ads.
• change-password (W3C): lets password managers send users straight to the page where they change their password. It counts when the build has the path as a file or folder, or _redirects has a rule from it. The fix suggests the first page with an autocomplete="new-password" field as target. A redirect set up on the server instead is invisible in the build: set the option to 'off'.
• apple-app-site-association: .well-known/ or the root, a JSON object with an applinks, webcredentials, appclips or activitycontinuation section.
• assetlinks.json: a non-empty JSON array of statements with relation and target.

These files live at the origin root, so with a siteUrl path (https://example.github.io/project/) the checks are skipped with a log line.

Example output

─── assets ──────────────────────────────────────────────────────

✖ og:image "/og/home.png" is not an absolute URL
    on: /
    → Use an absolute URL, e.g. <meta property="og:image" content="https://example.com/og/home.png">.

✖ manifest icon /icons/icon-512.png not found
    in: dist/site.webmanifest
    on: / /about/ /blog/ +9 more
    → Add /icons/icon-512.png to the build or fix its "src" in /site.webmanifest.

⚠ missing <meta name="twitter:card">
    on: /about/ /blog/ /contact/ +8 more
    → Add <meta name="twitter:card" content="summary_large_image"> to the <head>.

⚠ no <link rel="apple-touch-icon"> on any page
    → Add a 180x180 PNG and <link rel="apple-touch-icon" href="/apple-touch-icon.png">.

✖ assets: 4 problem(s) across 12 page(s) (0.1s)

A clean run ends with ✔ assets: 12 page(s), all assets in place.

Options

Top-level keys used: siteUrl, exclude.

import { defineConfig } from 'vidimus';

export default defineConfig({
  siteUrl: 'https://example.com',
  audits: ['i18n', 'csp', 'a11y', 'links', 'r12s', 'assets'],
  assets: {
    manifest: false,
    ogImage: { width: 1200, height: 600 },
    exclude: ['^/404(\\.html|/)?$', '^/embed/'],
  },
});

Arrays replace, so repeat the 404 pattern when you add to assets.exclude.

Common fixes

The head tags that pass every check:

<link rel="icon" href="/favicon.svg" type="image/svg+xml">
<link rel="icon" href="/favicon.ico" sizes="32x32">
<link rel="apple-touch-icon" href="/apple-touch-icon.png">
<link rel="manifest" href="/site.webmanifest">

<meta property="og:title" content="Pricing and plans">
<meta property="og:url" content="https://example.com/pricing/">
<meta property="og:image" content="https://example.com/og/pricing.png">
<meta name="twitter:card" content="summary_large_image">

Build the og:image and og:url from the same site URL your framework uses for canonical links (Astro.site in Astro, .Permalink or absURL in Hugo) so they stay absolute.

A minimal site.webmanifest, with a 512px icon:

{
  "name": "Example",
  "short_name": "Example",
  "start_url": "/",
  "display": "standalone",
  "background_color": "#ffffff",
  "theme_color": "#0f172a",
  "icons": [
    { "src": "/icons/icon-192.png", "sizes": "192x192", "type": "image/png" },
    { "src": "/icons/icon-512.png", "sizes": "512x512", "type": "image/png" }
  ]
}

Put the icons, the manifest, favicon.ico and apple-touch-icon.png (180x180) in the folder your framework copies to the build as is, usually public/ (static/ in Hugo). Add a 404.html page there or as a route; see Frameworks for where each one expects it.

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