What the checks mean

Unfurl shows how your page looks when someone shares it, and runs a set of checks alongside it. Below is what each warning means, why it matters and what to do about it.

og:title and og:description

If either is missing, every platform makes something up. Usually it grabs the first text it finds on your page, and that is rarely the line you would have picked.

Watch the length too. WhatsApp shows around 65 characters, Google reads about 160. So put the point first. A description that opens with a run-up is a truncated sentence with no content on the shortest preview.

The size of your og:image

Without an image your link becomes a bare line of text among posts that do have one. That is the difference between being noticed and being scrolled past.

Use 1200 by 630 pixels. That is the ratio LinkedIn, Facebook and X expect, so nothing gets cropped anywhere. Keep the file small: if the image loads too slowly a platform gives up and shows nothing after all.

A relative path or http on og:image

A platform fetches your image from its own servers, not from a visitor's browser. A path like /image.png means nothing there, because there is no page to resolve it against.

So use a full address, and use https. Several platforms refuse images served over http, and then the preview stays empty without anyone telling you why.

This is what someone using a screen reader hears instead of your image: og:image:alt on Facebook and LinkedIn, twitter:image:alt on X. Without it your preview is an empty rectangle to that visitor.

Describe what is in the image, not what the page is called. If the title is already in the preview, repeating it in the alt text is noise rather than help.

og:url and the canonical

The og:url is the address a platform files your page under. If it is missing, or differs from your canonical, the same page can be counted under several addresses and your shares scatter across variants with and without parameters.

Put the same address there as in your canonical. One page, one address.

twitter:card

Without this tag X falls back to the small card: a narrow strip with a tiny thumbnail beside it. With summary_large_image you get the large version, where your og:image actually gets room.

One line, and it is the only difference between a link that stands out and one that does not.

The meta description

If it is missing, Google writes a snippet from your page itself. That can turn out fine, but you have no say in it. And platforms that find no og:description fall back to this one, so you lose your safety net as well.

Same rule as above: the point in the first 65 characters, and keep the whole thing under 160.

The lang attribute on html

Without lang a screen reader does not know what language your page is in and picks the wrong pronunciation. Dutch text read by an English voice is close to unintelligible.

It is one attribute, <html lang="en">, and it is WCAG 3.1.1. If a page is in another language, put that page's language there.