# Look at the cards > goflag preview renders a page's share cards as seven consumers make them, so you can settle the questions no rule can answer. Five rules in the catalogue state a question and refuse to answer it. One of them asks whether your `og:image` survives being cropped to 1.91:1 — which is not something a rule can decide. It needs an eye. Until now that meant deploying, posting the link somewhere, and looking at what came out. ```bash goflag preview http://localhost:3000 ``` It crawls exactly as a normal run does, then writes `.goflag/preview.html`: one self-contained file showing what Google, Open Graph, X, LinkedIn, Slack, Discord and WhatsApp make of every page it read. It never gates. It exits `0` on a run full of findings, because looking at your own cards is not a check. Only a run that could not happen exits `2`. ## Opening it The command prints the path on stdout, alone, so it composes: ```bash open "$(goflag preview http://localhost:3000)" ``` **Leave the server running while you look.** The file loads your images from the origin it audited, so a card whose site has since stopped shows a broken image and its `alt` text — which looks like a defect in the preview and is not. If you booted the site with `--start`, goflag stopped it on the way out. Start it yourself, audit without `--start`, and it stays up: ```bash pnpm start & # and leave it goflag preview http://localhost:3000 --static ``` `--start` is still the right choice in CI, where nobody is looking and the file is an artefact. ## Seven surfaces, and how much each one is worth The surfaces are not equally documented, and the file says so on every card using the same [rigor scale](/docs/rules) the rules use. | Surface | Rigor | What the vendor actually publishes | | ---------- | ------------- | -------------------------------------------------------------------------- | | Open Graph | `vendor-spec` | 1200×630 recommended, 600×315 floor, 200×200 minimum, 8MB, 1.91:1 | | LinkedIn | `vendor-spec` | 1200×627 minimum, 1.91:1, 5MB — and a thumbnail below 401px wide | | WhatsApp | `vendor-spec` | under 600KB, ≥300px wide, ratio ≤ 4:1, title in two lines, description ~80 | | Slack | `guideline` | which tags it reads, and that the result is a "micro-approximation" | | Google | `heuristic` | that it truncates "to fit the device width", and no number at all | | X | none | nothing reachable — the card documentation is not public | | Discord | none | nothing at all about link unfurls | Three of the seven publish real geometry. Drawing all seven with the same confidence would be four unearned claims, so each card carries its own. Two consequences worth knowing before you trust another preview tool: - **Google is not a card.** No image, no ratio. `og:title` is one documented source for the title link; `og:description` is documented nowhere — the snippet comes from the page or from `meta description`. - **X has not shown a description since 4 October 2023.** The headline came back in January 2024 as small text laid over the image, and the description never did. Any tool still drawing three stacked rows is drawing a card that stopped existing years ago. ## What else is on the page **The head, field by field, with the tag each value came from.** When `og:title` is absent and the card falls back to ``, the file says so rather than quietly showing a title. **The image as goflag actually found it.** Declared dimensions, dimensions decoded from the file, the ratio against the band `og.image.ratio` scores, and what the URL answered when it was fetched. A card whose image 404s is drawn as a card whose image 404s. **Findings, pinned to the card they concern** — every `og.*`, `icons.*`, `title.*`, `description.*` and `canonical.*` finding on that page, with its severity and its rigor. Everything else stays in the report. **The route in its other languages**, when it has them: locale, `og:locale`, title, and the title's length in graphemes. This is where a translation that outgrew its card becomes visible — on this site's own home page the four locales run 53, 65, 68 and 68, and the card's size ladder reads exactly that number. **JSON-LD, shown and never judged.** No rule in the catalogue reads it, and [that is deliberate](/docs/limits). The panel lists each block, its `@type` values and any parse error, and passes no verdict. **What hydration changed in the `<head>`**, when goflag has two readings to compare. A `+` is a tag only the browser has — and unfurlers run no JavaScript, so a card drawn from one is drawn from something a crawler may never receive. When there is nothing to compare, the panel says "not established" rather than drawing an empty box that would read like a pass. ## The JSON, if you want it `--report` still writes the full report beside the HTML, and on a preview run it carries an extra section — [`extractions`](/docs/report#extractions--asked-for-with-auditoptionsextractions), what every page declared, which no other run emits. ```bash goflag preview http://localhost:3000 --report preview.json ``` `--json` and `--summary` are refused here, along with the gate flags: the command owns stdout and does not gate, so a flag that would change neither is rejected rather than accepted and ignored. ## What it is not It does not render your card — [`@goflag/og`](/docs/next) does that. The preview shows the image your site serves at the URL your page declares, exactly as a consumer would fetch it, and a site that uses no goflag library gets the same view. It also judges nothing new. Every verdict on the page comes from a rule that already existed; the file's contribution is the part no verdict can carry.