I checked the link-preview tags on 95 well-known sites. Under half were clean, and
nine sites developers use constantly have no preview tags at all.
If you have ever pasted a link into Slack and got a bare grey URL instead of a title
and image, this is why.
The result
Of 95 sites, 79 responded to an automated check (the rest blocked it). Of those 79:
| count | share | |
|---|---|---|
| Perfect (100/100) | 38 | 48% |
Missing og:title
|
18 | 23% |
Missing og:image
|
15 | 19% |
| No preview tags whatsoever | 11 | 14% |
og:image that returns an error |
1 | 1% |
Nine sites with zero preview tags
Each of these was re-checked by hand with a real Chrome user-agent to rule out
bot-blocking. All returned HTTP 200 with no og:* and no twitter:* tags:
- news.ycombinator.com
- python.org
- swift.org
- ruby-lang.org
- arxiv.org
- jstor.org
- arstechnica.com
- trello.com
- replicate.com
Hacker News having no link preview is almost a design statement. python.org,
swift.org and ruby-lang.org are harder to explain — those are the front doors of
three major languages, and every share of them renders as a naked URL.
The subtler failure
Missing tags are at least honest. The nastier case is tags that look fine but point
at an image that no longer loads — you keep sharing links believing the preview works,
because you never see what other people see. One site in the sample had exactly this.
Worth knowing: og:image needs an absolute URL. A relative path silently produces
no image on most platforms, and nothing in your own browser will ever warn you.
Method, and where it is weak
- 95 sites chosen for recognisability across dev tools, languages, SaaS, news, reference and community — not a ranked top-N list.
- Homepages only. Deeper pages often have tags the homepage lacks, so this measures the front door, not the whole site.
- 16 sites blocked the automated request. Blocked is reported as unknown, not as a score of zero — conflating "we could not check" with "this is broken" is the easiest way to produce a wrong number, and I hit that bug while building this.
- Two sites were dropped from the final list: one was rate-limited, and reddit.com returned 403 and 200 on different attempts, so its result was not stable enough to publish.
Check your own
I wrote the checker as an open-source tool. It validates Open Graph and Twitter Card
tags, confirms the preview image actually loads, and also checks robots.txt and
sitemap.xml. Free, no signup:
- Live: https://ogcheck.onrender.com
- Source (MIT): https://github.com/rahulatrkm/ogcheck
There is also a GitHub Action, so a build can fail when a page ships without a valid
preview — which is the only way I know to stop this regressing quietly.
If you run it on your own site and get a surprising result, I would genuinely like to
hear it — especially any false positives, since that is the part I most want to fix.
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