Stack playbook · Snapshot 23 October 2026
Squarespace: readiness playbook
What 137 measured sites on this hosted platform get right, where they fall short, and the Squarespace-specific steps that close each gap.
- Sites measured
- 137
- Median readiness index
- 66/100
- Profiles on this stack
- 4
detected from homepage HTML and headers
all sites: 64
top-50K sites
Readiness by lane
Enable
90/100
All sites 77
Harden
56/100
All sites 55
Accelerate
65/100
All sites 63
Recover
21/100
All sites 11
The Squarespace playbook
Gaps ordered by impact, with the platform-specific step where one exists.
HSTS kept for at least a year
8.8% observed · all sites 31%
Send Strict-Transport-Security on HTTPS responses. Start with a short max-age (for example 300 seconds), confirm every subdomain works over HTTPS, then raise it in steps to 31536000. Add includeSubDomains only when all subdomains are HTTPS. HSTS preload is optional and hard to undo; hstspreload.org itself does not recommend it by default.
Modern image formats in use
21% observed · all sites 40%
Serve WebP or AVIF with a JPEG or PNG fallback, either through an image CDN or by generating both formats at build time.
Guide: AVIF, WebP, JPEG, and PNG: Choose the Right Image Format
DMARC policy enforces quarantine or reject
31% observed · all sites 31%
Publish DMARC with p=none and a reporting address first, fix any legitimate senders that fail SPF or DKIM alignment, then move to quarantine and finally reject.
security.txt published
2.2% observed · all sites 5.5%
Publish /.well-known/security.txt with at least Contact and Expires fields, as RFC 9116 requires, and review it before it expires.
CAA records limit who can issue certificates
5.1% observed · all sites 11%
Publish CAA records naming every CA you actually use, including the CAs your CDN uses for managed certificates. Add an iodef contact if you want reports.
HTTP/3 advertised
5.8% observed · all sites 36%
Turn on HTTP/3 at your CDN. Browsers fall back to HTTP/2 automatically, so the risk is low.
Content Security Policy present
12% observed · all sites 31%
Start with Content-Security-Policy-Report-Only to see what would break, tighten the policy over a few weeks, then enforce it.
Guide: Payment Security and PCI DSS: What Website Owners Need to Know
No render-blocking scripts in <head>
42% observed · all sites 44%
Add defer to scripts that need the DOM, async to independent ones such as analytics, or move them to the end of the body.
Guide: Control Third-Party Scripts Before They Control Your Page
Where Squarespace sites lead
- X-Content-Type-Options: nosniff96% observedall sites 48%
- Structured data present95% observedall sites 53%
- Canonical URL declared97% observedall sites 70%
- Offscreen images lazy-loaded88% observedall sites 61%
A note on hosted platforms
On Squarespace, the platform controls much of the TLS, header and caching configuration. Owners mostly influence content-level checks such as images, structured data, social previews and the sitemap. Header-level gaps are worth raising with the platform.