Customer.io Fall Release
Ask your AI Agent what to test next, run experiments, and build in Design Studio. See what shipped in Customer.io's Q4 2026 release.
Estimated origin: United States
Added 12 Nov 2026
Analysed 12 Nov 2026
via 
What we found
- It sends five of the six security headers we check; the missing one is X-Frame-Options.
- Built with Sanity and Cursor, the site is hosted on Vercel.
- It welcomes AI crawlers and publishes an llms.txt.
Built with: 64 technologies · Scale-up stack
Embed this on your site
For light pages
<a href="https://firstsited.com/launch/xp8bsb2m/customerio-fall-release"><img src="https://firstsited.com/badge/xp8bsb2m/stack.svg" alt="Customer.io Fall Release tech stack on FirstSited" height="28"></a>
For dark pages
<a href="https://firstsited.com/launch/xp8bsb2m/customerio-fall-release"><img src="https://firstsited.com/badge/xp8bsb2m/stack.svg?theme=dark" alt="Customer.io Fall Release tech stack on FirstSited" height="28"></a>
How it fits together
Each technology runs on, or extends, the one it sits under.
Each technology links to its own page: which other new sites launched with it.
Site checks
| Custom title and meta description | |
| Open Graph tags (title, image, description) | |
| Twitter card meta tags | |
| Canonical URL declared | |
| Responsive viewport meta tag | |
| Favicon present | |
| Semantic HTML (nav, main, article) | |
| Page title is 66 characters Google only shows about 60 characters of the title in search results; aim for 50–60 to keep the whole thing visible. |
| Referrer-Policy via <meta name="referrer"> | |
| X-Frame-Options | |
| Permissions-Policy experimental | |
| X-Content-Type-Options | |
| Content-Security-Policy | |
| Strict-Transport-Security | |
| X-XSS-Protection deprecated, not counted |
| Privacy policy /legal/privacy-policy/ | |
| Terms of service /legal/feature-terms | |
| Consent manager Cookiebot |
Mentions: GDPR, CCPA, Cookies, Do Not Sell
| robots.txt | |
| sitemap.xml 571 URLs | |
| security.txt optional | |
| llms.txt | |
| ads.txt only for ad-funded sites | |
| humans.txt optional |
| llms.txt published | |
| No AI bots blocked in robots.txt | |
| Content-Signal ai-train = yes | |
| Content-Signal search = yes | |
| Content-Signal ai-input = yes | |
| Link headers api-catalog, service-desc |
| State | Record | Status |
|---|---|---|
| SPF ~all | Soft-fail (~all), common and accepted | |
| DMARC p=quarantine | Quarantine | |
| DKIM | Found | |
| MTA-STS | Not deployed | |
| TLS-RPT | Not configured |
Hosting and network
| Network | AMAZON-02 - Amazon.com, Inc., US AS16509, US |
|---|---|
| DNS | AWS Route 53 authoritative nameservers |
| DNSSEC | Not enabled DNS answers are unsigned |
| Certificate | Let's Encrypt valid 25 Oct 2026 to 23 Jan 2027, as captured |
| Green hosting | No record per The Green Web Foundation |
| Page build | 43 JS files, 2 CSS files 5 third-party domains, code splitting |
| App manifest | Customer.io Engagement Platform display standalone; 4 icons; business, productivity |
| Brand colours |
Storage: 19 items
| Name | Lifetime | Set by |
|---|---|---|
| ajs_anonymous_id | 12mo | Segment |
| cio_u_id | 1y | Customer.io |
| embed_url | 29d | - |
| _cio_marketing_analytics | 1y | Customer.io |
| Key | Size | Set by |
|---|---|---|
| ajs_anonymous_id | 38 B | Segment |
| ajs_user_id | 4 B | Segment |
| embed_url | 58 B | - |
| gist.web.customAttributes | 107 B | Customer.io |
| gist.web.guestUserToken | 84 B | Customer.io |
| gist.web.inbox.enabled | 51 B | Customer.io |
| gist.web.inbox.messages.5c24365f5542b86ea1bad008473cade7fe17bd9849584c6ed5e85222358547e8 | 48 B | Customer.io |
| gist.web.message.broadcasts.5c24365f5542b86ea1bad008473cade7fe17bd9849584c6ed5e85222358547e8 | 12.5 KB | Customer.io |
| gist.web.message.user.5c24365f5542b86ea1bad008473cade7fe17bd9849584c6ed5e85222358547e8 | 48 B | Customer.io |
| gist.web.sessionId | 84 B | Customer.io |
| gist.web.userQueueNextPullCheck | 49 B | Customer.io |
| gist.web.userQueueUseSSE | 51 B | Customer.io |
| gist.web.userToken | 84 B | Customer.io |
| gist.web.usingGuestUserToken | 50 B | Customer.io |
| Key | Size | Set by |
|---|---|---|
| gist.web.isPersistingSession | 4 B | Customer.io |
Performance
| Measure | This site | Reading |
|---|---|---|
| Server response | 260 ms | good, faster than 50% of sites |
| Largest contentful paint | 576 ms | good |
| Layout shift | 0.05 | good |
| Page weight | 3.4 MB | heavy |
| Image weight | 153 KB | light |
| Images | 14 | 5 larger than shown |
| Third-party domains | 5 | |
| Console errors | 3 | worth a look |
| Failed requests | 1 | worth fixing |
Broken requests to the site itself (1), worth fixing
- 404 /llms.txt?_rsc=2xefgHINwu_qcQvV
From a single automated render of the home page. A quick guide, not a substitute for Lighthouse or field data. How we measure
Notes
-
Looks AI-built: strong AI signals.
How much the site looks AI-generated. It is a pattern match shown for interest, not a verdict.
Which signals fired
Signal Points AI copy signals +5 Recognised AI builder signature +100 AI layout signals +5 Unfilled template placeholders +10 - Performance comes from one render on 12 November 2026 and will vary between visits.
How we know
FirstSited records what new websites are built with, usually within a day of going live. Most we find ourselves, by watching public internet infrastructure for brand-new sites; the rest come from Product Hunt, Hacker News and PeerPush. We checked this one in full: its tech stack, DNS, security headers and page basics. This page is what we saw on 12 November 2026; the live site may have changed since.
Every technology below links to its own page: which other new sites launched with it. Watch any of them and get every new site that uses it as it goes live, from £15 a month.