jupyter.org

Readiness by lane

Green: jupyter.org. Thin bar: Programming & Software peer median.

Priority fixes for jupyter.org

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

1. Priority 1 · Harden

   HSTS kept for at least a year

   Observed: The homepage response did not include a Strict-Transport-Security header.

   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 Fastly: Add the header in VCL or a header rule as described in Fastly's HSTS guide.

   40% of Programming & Software 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 600 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.

   50% of Programming & Software peers do this.

   Guide: Browser Caching Guide for Website Owners

3. Priority 3 · Harden

   DMARC policy enforces quarantine or reject

   Observed: The DMARC policy for jupyter.org was p=none, which asks receivers to take no action on failing mail.

   What to do: 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.

   45% of Programming & Software peers do this.

   Guide: A Practical Website Health Check for Owners

4. Priority 4 · Accelerate

   No render-blocking scripts in <head>

   Observed: The homepage <head> loaded 1 external script 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.

   51% of Programming & Software peers do this.

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

What jupyter.org already does well

Practices fewer than half of Programming & Software peers use.

• security.txt publishedsecurity.txt with a contact found.15% of peers
• Modern image formats in useWebP or AVIF images detected.42% of peers

What we saw

Homepage checked

https://jupyter.org/

Homepage response

HTTP 200

TLS

TLSv1.3, HTTP/2

Certificate

Let's Encrypt, 89-day validity, expiring 2027-01-17

CDN or edge

Fastly, GitHub Pages

DNS operators

Cloudflare

DMARC policy

p=none

Homepage HTML

37 KB, gzip

Images on homepage

47 (svg 46, webp 3, 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 Programming & Software sites

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• wokwi.com63

Programming & Software readiness benchmark