Which tags still matter
The tags that do real work are few. <title> is the strongest on-page signal you control and the headline in search results. The meta description does not influence ranking, but it does influence click-through, because it usually becomes the snippet — and search engines rewrite it when they judge a different extract more relevant to the query, so treat it as a strong suggestion rather than a guarantee.
The meta keywords tag is dead. Google has ignored it since 2009 and it does nothing but disclose your targeting to competitors. The canonical link, by contrast, matters a great deal: it tells engines which URL is authoritative when the same content is reachable through several, consolidating ranking signals rather than splitting them across duplicates.
The viewport meta tag is not an SEO tag but has more practical impact than most: without it, mobile browsers render at a desktop width and scale down, producing an unusable page. Its absence is one of the clearest mobile usability failures a page can have.
Lengths, truncation and writing for the snippet
Search results are measured in pixels rather than characters, so limits are approximate. Titles are typically truncated somewhere around 580 pixels, which works out near 55 to 60 characters — fewer with wide capitals. Descriptions have roughly 155 to 160 characters on desktop and less on mobile.
Front-load the meaningful words. A title beginning with a brand name spends its most visible characters on something the reader may already know, whereas the distinguishing term belongs first. Every page needs a unique title and description; duplicates across a site are a common and easily fixed quality problem, and generating them from a template produces exactly the kind of near-identical text that reads as automated.
Write descriptions as an invitation rather than a summary. A description that states what the page offers and why it answers the query outperforms a keyword-stuffed one, which search engines are likely to discard in favour of their own extract anyway.
Open Graph, Twitter cards and structured data
Social previews use their own tags. Open Graph — og:title, og:description, og:image, og:url, og:type — is honoured by Facebook, LinkedIn, WhatsApp, Slack, Discord and most others. Twitter reads twitter:card and its siblings but falls back to Open Graph when they are absent, so the Open Graph set alone covers nearly everything.
The image is what determines whether a shared link looks credible. Aim for 1200 × 630, use an absolute URL, and remember that platforms cache aggressively — a preview will keep showing an old image until the cache expires or you clear it in that platform's debugging tool. The social card preview shows how a link will actually render before you publish it.
Structured data in JSON-LD is separate from meta tags and is what generates rich results — review stars, FAQ accordions, breadcrumbs, article bylines. It must describe content genuinely visible on the page; marking up content that is not there is a policy violation and results in a manual penalty rather than a richer listing.