The head of a page decides how it is introduced before anyone reads it: the title and description in a search result, the card that appears when a link is shared, the instructions to crawlers. Getting those tags right is cheap, and getting them wrong is invisible from the page itself, which is why every tool in this group shows you the result the way a reader or a crawler will meet it.
Start with the meta tag generator when writing tags for a new page: it is a title tag generator and a meta description generator in one, and writes the whole block with a live preview. To check how a title will really fit, use the SERP snippet preview. Google truncates by pixel width, not by character count, so a title full of capital Ms runs out of room long before one made of narrow letters; the preview measures every field in pixels, at desktop width and as a phone shows it, and marks where the cut falls.
For a page that already exists, paste its source into the meta tag analyzer. It reads the whole head and grades each tag — title and description length, charset, viewport, robots directives, the canonical link — which makes it the quickest way to audit a template you inherited and to catch a stray noindex before it costs traffic. Google rewrites titles and descriptions it considers inaccurate or stuffed, so the aim is a title that describes the page honestly at a length that fits, not one engineered around a number.
The Open Graph generator writes the og: and Twitter card tags that control the preview on LinkedIn, Slack, WhatsApp, X and Facebook. Use an image of 1200 by 630 pixels, give it an absolute URL, and make sure the server sends it with an image content type: a card silently loses its picture when the file arrives as application/octet-stream. Platforms cache the first version they fetch, often for days, so check the tags before a link is shared rather than after.