Security-header advice has been the same for a decade: set HSTS, set a CSP, add X-Frame-Options and nosniff, done. I wanted to know how many sites that actually reach the biggest audiences on the web bother. So I took the Tranco top 1,000, fetched every homepage once, and graded six response headers.
Short version: the median security-header score is 37 out of 100. Fewer than 1 in 10 of the top sites score 70 or higher, and 13% send no security headers at all. The full dataset and scripts are on GitHub, there is an interactive version with a searchable table of every domain, and this post is the walk-through.
How the scan works
One GET https://<domain> per site, redirects followed, then six headers each graded missing / weak / reasonable / strong:
Strict-Transport-SecurityContent-Security-PolicyX-Frame-OptionsX-Content-Type-OptionsReferrer-PolicyPermissions-Policy
The score is the mean of the six grades as a percentage. The one nuance worth stating: a CSP containing unsafe-inline, unsafe-eval or a wildcard source is graded weak, not strong. It parses, but it does not stop injected script from running.
I did the fetching and grading with an open-source API I maintain (the Web Metadata & Contact Extractor), because one call to its /api/v1/extract endpoint returns the header grades, an overall security score, an SEO score and a detected tech stack for a URL. That last part matters for the third finding below.
About the denominator
Of the 1,000 domains, only 489 are real, reachable homepages. 225 are infrastructure (DNS-only CDN and cloud domains that serve no site), 209 were unreachable from where I ran the scan (timeouts, geo-blocks, paywalls, apex redirect quirks), 43 returned a bot-challenge or WAF page, and 34 served a placeholder. Every number below is over those 489. The sites I could not read lean toward the heavily bot-protected, which are on average the more security-conscious ones, so the real picture is probably a little worse than this.
Finding 1: most of the top sites are missing most of the headers
Strict-Transport-Security is the only header on a majority of sites (71%). X-Frame-Options and X-Content-Type-Options - each a single static line with no downside - are missing on roughly 45%. Referrer-Policy is on 29%. Permissions-Policy is on 16%.
Finding 2: the score distribution is bottom-heavy
Median 37, mean 36, and a long tail into the low scores rather than the high ones. A quarter of the top 1,000 score 17 or below.
Content-Security-Policy is where it breaks down hardest. 46% of sites have no CSP at all. Of the 54% that do, all but 90 sites carry unsafe-inline or a wildcard. Put together, about 82% of the top 1,000 have no browser-enforced CSP that would actually stop an XSS. Three sites in the whole set have a CSP I would call strong.
That is not all negligence. A strict CSP on a large existing site is genuinely hard - third-party tags, inline handlers, A/B tools all fight it, and a bad rollout breaks the page. But "hard" is the explanation for the weak-CSP half, not for the 46% with nothing and the 84% with no Permissions-Policy.
Finding 3: the tech stack predicts the posture
Bucketing the 489 sites by detected platform, WordPress (n=44) sits about 10 points below the field: median score 27, and 61% ship no CSP versus 46% overall. Next.js and similar framework/edge stacks land near or just above the median, mostly because their hosting (Vercel, Netlify, Cloudflare Pages) sets a decent HSTS by default. The only groups with a median above 42 were Astro (n=8, too small to lean on) and Drupal (n=10).
The interesting part is what happens inside the WordPress bucket. Those 44 sites have a median SEO score of 83, well above the overall 75. They are not neglected sites. They are sites where SEO got attention and headers did not.
Finding 4: SEO effort and security effort barely correlate
Across all 489 sites, Pearson r between the SEO score and the security-header score is 0.17. The top of the web has largely solved SEO (median 75) and largely skipped security headers (median 37), and knowing how much a team invested in one tells you almost nothing about the other.
My read: SEO has a tight, visible feedback loop (rankings, traffic, revenue). Security headers have none until an incident. So on a busy roadmap the headers lose, every sprint, at almost every company - including ones with the resources to know better.
Try it on your own site
pip install httpx matplotlib
curl -sL -o tranco.zip https://tranco-list.eu/top-1m.csv.zip
python scan.py 1000 # -> results.jsonl
python analyze.py # -> summary.json + top1000-web-report.csv
python make_charts.py
Everything - the scan script, the analysis, the raw JSONL, the flattened CSV - is in the repo under MIT. If you just want your own site graded, the API has a free tier and curl ".../api/v1/security?url=https://yoursite.com" gives you the same per-header grades used here.
If you find a bug in the grading or want a rank band or a platform I did not break out, open an issue with the dataset row and I will take a look.
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