How to add Strict-Transport-Security on Lovable / static hosting

Last updated November 11, 2026 · Reviewed by a CISSP-certified security practitioner

To add Strict-Transport-Security on Lovable / static hosting, set the header in src/server.ts (TanStack Start) or your edge proxy with the value max-age=63072000; includeSubDomains; preload. Forces browsers to only use HTTPS for your domain. Publish, then curl -I your live domain. Then confirm it with curl -I or a free FixSecurityHeaders scan.

What does Strict-Transport-Security do?

HSTS tells the browser to always connect over HTTPS for a set time, even if someone types http:// or clicks an old link.

Risk if missing: Without it, the first request can be downgraded to plain HTTP, letting attackers on public Wi‑Fi intercept or rewrite traffic (SSL stripping).

What is the Lovable / static hosting configuration?

Add this to src/server.ts (TanStack Start) or your edge proxy:

src/server.ts (TanStack Start) or your edge proxy

// src/server.ts — wrap the response before returning it
function withSecurityHeaders(res: Response): Response {
  const out = new Response(res.body, res);
  const h = out.headers;
  h.set("Strict-Transport-Security", "max-age=63072000; includeSubDomains; preload");
  return out;
}

How do I add it step by step?

Open src/server.ts (TanStack Start) or your edge proxy.
Paste the Strict-Transport-Security configuration shown below.
Publish, then curl -I your live domain.
Run curl -I https://yourdomain.com and look for the strict-transport-security line.
Scan your site on FixSecurityHeaders to confirm the grade improved.

How do I verify it worked?

terminal

curl -sI https://yourdomain.com | grep -i "strict-transport-security"
# expected:
# strict-transport-security: max-age=63072000; includeSubDomains; preload

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What are the common mistakes?

The preload directive is hard to undo: removal from browser preload lists takes months.
includeSubDomains breaks any subdomain that still serves plain HTTP. Audit subdomains first.
Start with a short max-age (e.g. 300) and ramp up to 1–2 years once verified.
Browsers ignore HSTS sent over plain HTTP; it must be sent on the HTTPS response.
Pure static hosts that don't allow custom headers can be fronted by Cloudflare to add them.
Skip frame-blocking headers on preview URLs that are shown inside editors.

Quick reference

Header	`Strict-Transport-Security`
Recommended value	`max-age=63072000; includeSubDomains; preload`
Stack	Lovable / static hosting
Where	src/server.ts (TanStack Start) or your edge proxy
Compliance	PCI DSS 4.0 4.2.1, NIST 800-171 3.13.8, CMMC SC.L2-3.13.8, OWASP ASVS V14.4.5, SOC 2 CC6.7

FAQ

What value should I use for Strict-Transport-Security?

A safe default is max-age=63072000; includeSubDomains; preload. The preload directive is hard to undo: removal from browser preload lists takes months.

Why isn't Strict-Transport-Security showing up on Lovable / static hosting?

Pure static hosts that don't allow custom headers can be fronted by Cloudflare to add them. Also clear any CDN or page cache, and check you edited the config that actually serves your domain.

Does Strict-Transport-Security affect SEO or performance?

No measurable performance cost — it's a few bytes per response. It doesn't affect rankings directly, but a misconfigured policy can break page resources, so test before enforcing.

Which compliance frameworks reference Strict-Transport-Security?

PCI DSS 4.0 4.2.1, NIST 800-171 3.13.8, CMMC SC.L2-3.13.8, OWASP ASVS V14.4.5, SOC 2 CC6.7.