jcom.co.jp

Readiness by lane

Green: jcom.co.jp. Thin bar: Telecommunications & Internet peer median.

Priority fixes for jcom.co.jp

Ordered by impact and by how common each practice is among peers.

1. Priority 1 · Harden

   HSTS kept for at least a year

   Observed: Strict-Transport-Security was sent with a max-age of 7 days, below the one-year benchmark.

   Why it matters: HSTS tells browsers to use HTTPS for your host on every later visit, which removes the window where a first HTTP request can be intercepted.

   What to do: 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.

   On Cloudflare: Enable HSTS under SSL/TLS > Edge Certificates > HTTP Strict Transport Security and raise max-age gradually.

   54% of Telecommunications & Internet peers do this. Limit: Read from the homepage response only; other pages or regions may send different headers.

   Guide: HTTPS and TLS Guide for Website Owners

2. Priority 2 · Accelerate

   Static files cached for 30 days or more

   Observed: A same-site stylesheet or script was cacheable for 300 seconds, short of the 30-day benchmark.

   What to do: Give versioned (fingerprinted) CSS, JavaScript, fonts and images Cache-Control: public, max-age=31536000, immutable, and change the file name whenever the content changes.

   On Cloudflare: Use Cache Rules to set edge and browser TTLs for static file paths.

   41% of Telecommunications & Internet peers do this.

   Guide: Browser Caching Guide for Website Owners

3. Priority 3 · Accelerate

   No render-blocking scripts in <head>

   Observed: The homepage <head> loaded 6 external scripts without async or defer.

   What to do: Add defer to scripts that need the DOM, async to independent ones such as analytics, or move them to the end of the body.

   37% of Telecommunications & Internet peers do this.

   Guide: Control Third-Party Scripts Before They Control Your Page

4. Priority 4 · Harden

   Content Security Policy present

   Observed: The homepage response did not include a Content-Security-Policy header.

   What to do: Start with Content-Security-Policy-Report-Only to see what would break, tighten the policy over a few weeks, then enforce it.

   48% of Telecommunications & Internet peers do this.

   Guide: Payment Security and PCI DSS: What Website Owners Need to Know

What jcom.co.jp already does well

Practices fewer than half of Telecommunications & Internet peers use.

• Nameservers spread across providersNameservers spread across more than one operator.16% of peers
• Reachable over IPv6IPv6 address published.33% of peers

What we saw

Homepage checked

https://www.jcom.co.jp/

Homepage response

HTTP 200

TLS

TLSv1.3, HTTP/2

Certificate

GlobalSign, 199-day validity, expiring 2026-12-12

CDN or edge

Cloudflare

DNS operators

2 self-run or other nameserver domains

HSTS

max-age 7 days

DMARC policy

p=quarantine

Homepage HTML

497 KB, gzip

Images on homepage

215 (svg 161, webp 64, png 3)

Limits: homepage only, one location, one moment. Header checks reflect the homepage response; other pages may differ.

Stack and providers

Seen in the homepage response, certificate and DNS. Provider pages compare how their customers configure the same checks.

All 31 checks

Select a gap for the method and fix. How each check works

Compare with other Telecommunications & Internet sites

• comviq.se71
• free.fr71
• hmd.com71
• mci.ir71
• orange.be71

Telecommunications & Internet readiness benchmark