Why Google cuts titles by pixels, not characters
Search results have a fixed width, so what fits depends on the letters you use: "WWW" takes far more room than "iii". A character count is only a rough guide. This tool measures your text with your browser's canvas in Arial at 20 px for the title and 14 px for the description, the sizes desktop results have used for years, and compares it with about 580 px for titles and about 920 px for descriptions. Those limits are approximate and change with Google's design. Google may also rewrite a title or pick another snippet from the page when it thinks it matches the search better, so treat a green meter as "likely to show in full", not a promise.
SERP preview for Arabic pages, right to left
When the title is Arabic, the preview switches to right-to-left, as an Arabic result does: the site name and title are aligned to the right and an Arabic title is cut on its left side. Arabic letters join and change shape, so their width cannot be guessed from the number of characters; measuring them is the only reliable check. Arabic text stays as plain UTF-8 in the code, which is what browsers and search engines expect, and the checks remind you to set og:locale to an Arabic value and to mark the page with lang="ar" and dir="rtl".
What each tag does
The title tag is the headline of the result and the tab name. The meta description is a suggestion for the text under it. The canonical link tells search engines which address is the main one when the same content is reachable at several URLs, for example with tracking parameters. The robots tag can keep a page out of the index (noindex), stop link following (nofollow), or limit snippets. The viewport tag makes the page fit phone screens. Open Graph tags (og:title, og:description, og:image, og:url) control the card shown when the link is shared on WhatsApp, Facebook or LinkedIn, and twitter:card tags do the same on X.
Checks that catch common mistakes
Beyond length, the tool warns when the title and description are identical, when a word is repeated by accident, when the site name appears twice in the title, and when the canonical or share image URL is relative or carries a # fragment, which search engines ignore. It flags noindex and nosnippet because they are easy to leave on by mistake after a staging site goes live. Every value is escaped, so quotes and ampersands in a title such as Tom's "Best" Deals cannot break the HTML. For structured data, use the schema markup generator; for clean URLs, the slug generator.