Slack, iMessage, LinkedIn, and Facebook do not scrape your <h1>. They look for Open Graph tags. If og:title is still the homepage default, the unfurl will say the brand name no matter how good the article is. If og:image is missing or smaller than about 1200×630, you get a sad square or nothing.
Also Read: SEO and Web
The tags that actually get read
og:type (usually article or website), og:title, og:description, og:url as the canonical, og:image, og:site_name as the brand. Twitter wants twitter:card (summary_large_image unless you have a reason not to) plus title, description, and image. You can reuse the OG values.
Also Read: SEO: UTM parameters that
The meta tag and OG preview generator fills those fields, shows a rough card, and gives you a copyable block. It will not fetch Slack’s cache. After you deploy, use Slack’s own cache-refresh if an old title is stuck.
Also Read: Moving Apache Redirect and RewriteRule lines to nginx
Campaign URLs and the canonical
og:url should be the canonical without UTM junk. Put tracking on the link you paste into the newsletter, not on the tag that tells Facebook what the page is. Build the tracking link with the UTM campaign builder so source/medium/campaign stay lowercase and hyphenated.
If the unfurl image is right and the title is still wrong, view source. A plugin or a layout default is winning. The generator is for the snippet you meant to ship, not for debugging three layers of SEO packages.
