what these tags do, and what they don't

Two audiences: the human choosing, the machine reading.

A head block does two jobs. The title and description are a pitch to the person scanning ten results. The canonical and Open Graph tags are instructions to machines about which page is real and what the shared link should look like. Neither one is a magic ranking lever, and any tool that sells them that way is selling folklore.

Length is a display limit, not a ranking ruleThere is no character count Google enforces. The familiar "keep titles near 60 characters" is a rough translation of the roughly 600 pixels a desktop result gives a title before it clips. We count characters as a quick guide, but pixels are the real limit, which is why the snippet preview measures your actual words in the actual font.
Google rewrites titles often, so the H1 mattersIndependent measurement has found Google rewriting a majority of title tags, usually trimming boilerplate or swapping in the page's own H1. You cannot stop a rewrite, but you can control what Google reaches for: keep the title and the H1 telling the same story.
The description does not rank you, it earns the clickGoogle has said for years the meta description is not a ranking factor, and it frequently replaces it with on-page text that matches the query better. Write it for the human comparing results, and make the page say the same thing so a substitution still reads well.
Open Graph controls the preview, not the rankingog:title, og:description and og:image decide what your link looks like when it is pasted into a message, a social post, or an AI chat. A missing og:image gives you a bare, low-trust preview. These tags never move your position; they move whether the link gets clicked once it is shared.
Canonical resolves duplicates, it does not force indexingThe canonical tag names the version of a page you want credited when several URLs show the same content. It is a strong hint, not a command, and it is not a substitute for noindex or a redirect. Point it at the wrong page and you can hand your ranking signals to a URL you did not mean.

meta tag questions, answered straight

The honest version.

How long should my title tag and meta description be?

There is no official character limit, because Google does not enforce one. Titles get roughly 600 pixels of width on desktop before they clip, which lands most titles near 50 to 60 characters, and descriptions clip after about two lines, near 150 to 160 characters. Treat those as display guides, not rules: front-load the words that matter so the meaning survives a cut, and remember that Google can and does rewrite both. The counter on this page flags when you are past the usual clip point, not because longer ranks worse, but because the reader stops seeing your pitch.

Do I still need Open Graph and Twitter tags if I have a title and description?

Yes, if you care how your links look when shared. Search results use your title and description, but messaging apps, social platforms and AI chats build their link previews from Open Graph tags, falling back to Twitter card tags. Without og:title, og:description and og:image, a shared link renders as a bare URL or a stripped-down box, which quietly lowers how often people click it. The tags do not affect ranking; they affect the click on every surface that is not a search result.

What is a canonical tag and can it hurt me?

A canonical tag tells engines which URL is the primary version of a page when the same content is reachable at several addresses. Used well, it consolidates your ranking signals onto one URL instead of splitting them. Used carelessly, it can hurt: pointing every page at your homepage, or at a competitor's domain, tells Google to credit that page instead of the one someone is on. It is a hint Google usually honors, so set it to the page's own clean address unless you have a specific reason not to. You can verify it live with the canonical checker.

a few tags of the whole picture

Clean tags win the click. We check the whole page.

A good head block earns the click and a clean preview. Whether Google and the AI engines can actually reach, read, trust and cite the page behind it is a different question, and it is the one the full AuditLamp audit answers: 116 documented checks across search, answer boxes and AI assistants, ranked by what is costing you customers. Full score on screen in about thirty seconds, no email taken.