seo

import {
  canonicalUrl,
  pageHead,
  renderHeadTags,
  SEO_DESCRIPTION_MAX,
  SEO_TITLE_MAX,
  shareImageSource,
  type PageHead,
  type PageHeadInput,
} from "louise-toolkit/seo";

The Settings panel stores a meta description, a default share image, a favicon, and Hide from search engines, and every page row has an SEO title, description, share image, and noindex. None of them does anything until a page prints it. pageHead decides every head tag from those rows and the request, and renderHeadTags serializes the result with every value escaped. It’s pure, with no bindings, so it runs in any framework and in a unit test.

`pageHead(input)`

function pageHead(input: PageHeadInput): PageHead;

Input	What it is
`page`	The page row. A `pages` row fits as it is.
`settings`	The `site_settings` row, or `null`.
`origin`	The site’s origin, for example, `https://example.com`.
`path`	The request’s path, with or without its query string.
`titleTemplate`	`(pageTitle, siteName) => string`. Omit to use the page’s title as it is.
`homeSlug`	The slug the site serves at `/`. Its canonical URL is the origin’s root.
`keepParams`	Query parameters the page’s content depends on. The canonical URL keeps these, sorted.
`shareCardUrl`	`(slug, title) => string`, the site’s generated share card. Omit when it renders no cards.
`icon`	The favicon when the settings have none.
`ogType`	`og:type`. Default `"website"`.

Each tag falls back in a fixed order:

Title: the SEO title, then the title, through titleTemplate. The separator is the site’s choice; the house style is a pipe, as in About | Example Organization. og:title is the page’s own title, without the site name, which goes in og:site_name.
Description: the SEO description, then the body’s text clamped to SEO_DESCRIPTION_MAX, then the site-wide meta description. When none of them has text, the tag is left out rather than printed as content="".
Robots: noindex when the page’s noindex or the site’s Hide from search engines is on.
Canonical: see canonicalUrl.
Share image: see shareImageSource. The result is an absolute URL, and anything that isn’t http or https is dropped. twitter:card is summary_large_image with an image and summary without.
Icon: the settings’ favicon, then icon.

`renderHeadTags(head)`

function renderHeadTags(head: PageHead): string;

The head as HTML, one tag per line: <title>, the description, robots, canonical, icon, Open Graph, and twitter:card. Every value is escaped. Print it inside <head> as raw HTML; the charset and viewport stay the page’s own.

`canonicalUrl(origin, path, keepParams?)`

The origin plus the path, with every query parameter dropped except keepParams, which stay sorted, and the fragment removed. A page’s content doesn’t vary by its query string, so without it every ?utm_source=… variant is another indexable copy. It shares its query handling with the edge cache key.

`shareImageSource(input)`

function shareImageSource(input: {
  ogImage?: string | null;
  cards?: boolean;
  defaultImage?: string | null;
}): { kind: "image"; src: string } | { kind: "card" } | { kind: "none" };

What a share of a page shows, in order: the page’s own ogImage, then the site’s generated card when it renders one, then the site-wide default image. The Pages panel’s share preview uses the same function, so the preview shows what a share gets. Pass ogCard: false in the Settings config when your site renders no cards, and the preview falls back to the default image the way a share does.

Limits

SEO_TITLE_MAX (60) and SEO_DESCRIPTION_MAX (155) are where search results cut off. metaDescription(), suggestSeo, pageHead, and the Pages panel’s character counts all read them. louise-toolkit/ai exports the same two constants.

With Astro

@louise-toolkit/astro exports seoHead(Astro, input), which fills origin and path from the request and returns the rendered tags. The origin is input.origin, then the configured site, then the request’s own origin; set site in astro.config so a preview host can’t leak into the canonical URL.

---
import { seoHead } from "@louise-toolkit/astro";

const head = seoHead(Astro, {
  page,
  settings,
  homeSlug: "home",
  titleTemplate: (title, site) => (site ? `${title} | ${site}` : title),
  shareCardUrl: (slug, title) =>
    `/og.png?slug=${encodeURIComponent(slug)}&title=${encodeURIComponent(title)}`,
  icon: "/favicon.svg",
});
---

<head>
  <meta charset="utf-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1" />
  <Fragment set:html={head} />
</head>

Build shareCardUrl from the same slug and title your publish step warms, so the first share of a page is a cache hit.