Fixing SSL Error Vercel

That error means the SSL certificate presented by your site doesn’t match the domain name being visited . On Vercel this is usually quick to fix, but the cause matters. Below is the practical, Vercel-specific checklist (ordered from most common → least). 1. Check the exact domain that’s failing (most common) The cert must match exactly . Common mismatches: www.example.com vs example.com https://example.com works but https://www.example.com fails Subdomain missing from Vercel ( app. , beta. , etc.) Fix Go to Vercel Dashboard → Project → Settings → Domains Make sure every variant you expect works is listed: example.com www.example.com (if used) Any subdomains 👉 Vercel issues certs per-domain , not “automatically for all variants”. 2. Domain not fully verified yet If DNS is partially wrong, Vercel may fall back to a default cert , causing this error. Fix In Settings → Domains , look for: ❌ “Invalid Configuration” ⏳ “Pending Verification” Click “View DNS Records” and ensure: A / CNAME records match exactly what Vercel shows No extra conflicting records Typical setup: example.com → A record to 76.76.21.21 www.example.com → CNAME to cname.vercel-dns.com 3. Old / conflicting DNS records (very common) This happens if the domain was previously on: Netlify Cloudflare AWS Another Vercel project Fix At your DNS provider: Remove all old A, AAAA, and CNAME records There should be only one target per hostname ⚠️ Especially check for: AAAA (IPv6) records Hidden @ records Cloudflare “orange cloud” proxy (see below) 4. Cloudflare proxy causing cert mismatch If you’re using Cloudflare and it’s set to Proxied (orange cloud) , Cloudflare presents its cert — which may not match. Quick test Temporarily set: DNS → Proxy status: DNS only (grey cloud) If the error disappears, that was the issue. Proper fix Either: Use Cloudflare Full (Strict) SSL Or let Vercel handle SSL directly (recommended unless you need CF features) 5. Certificate hasn’t finished provisioning Vercel certs usually issue in minutes, but sometimes hang. Fix Remove the affected domain in Vercel Re-add it Wait ~5–10 minutes Hard refresh (or test in incognito) 6. Browser / OS cache (rare but real) Especially on macOS. Test Open in Incognito Test from another device Run: Bash openssl s_client -connect example.com:443 -servername example.com Check CN= or SAN= values. 7. You’re hitting the wrong project If multiple Vercel projects use similar domains, you might be routing to the wrong one. Fix Ensure: Domain is assigned to only one Vercel project No “shadow” deployments using the same hostname Fast diagnosis (recommended) Tell me: The exact domain showing the error Whether you’re using Cloudflare Screenshot or text from Vercel → Domains status I can pinpoint the exact misconfiguration in one pass. TL;DR (90% of cases) You added example.com but are visiting www.example.com , or DNS is pointing to the wrong place. Fix the domain entry in Vercel and clean up DNS — the cert error disappears automatically.

Short answer: you can use demo.yseeku.com for GitHub Pages , but only if you do it intentionally and cleanly . What you cannot do is let it overlap or be caught by Vercel’s wildcard in a half-configured way. Right now, you’re almost there — you just need to be clear about ownership. The rule (this is the key idea) Each hostname must be owned by exactly ONE platform. Vercel and GitHub Pages must never both think they serve the same name. Apex + www → Vercel demo.yseeku.com → GitHub Pages That is a perfectly valid setup. Your current setup (based on the screenshot) You have: demo → CNAME → s8ken.github.io * → ALIAS → cname.vercel-dns.com This is the subtle part: demo.yseeku.com does win over * (explicit beats wildcard) So DNS-wise, demo.yseeku.com correctly goes to GitHub Pages SSL-wise, GitHub Pages will issue its own cert if configured So DNS is OK — the remaining requirement is GitHub Pages config . What MUST be true for this to work 1. GitHub Pages must explicitly know about demo.yseeku.com In the GitHub repo used for Pages: Go to Settings → Pages Custom domain: demo.yseeku.com Ensure the repo contains a CNAME file with: demo.yseeku.com Without this, GitHub Pages serves a cert for *.github.io , not your subdomain → cert error. 2. Do NOT add demo.yseeku.com to Vercel In Vercel: Do not add demo.yseeku.com as a domain Let it exist only in DNS + GitHub This avoids Vercel trying to issue a cert for it. 3. Wait for GitHub SSL provisioning GitHub Pages SSL: Can take up to ~1 hour Uses Let’s Encrypt You’ll see “ HTTPS enforced ” toggle appear Once that’s on, the cert will be valid. Safe mental model Hostname Platform yseeku.com Vercel www.yseeku.com Vercel demo.yseeku.com GitHub Pages docs.yseeku.com GitHub Pages (if desired) everything else Vercel wildcard That model is stable and production-safe . When you would get the cert error again You’ll see ERR_CERT_COMMON_NAME_INVALID if: You add demo.yseeku.com to Vercel and GitHub You forget the GitHub Pages custom domain step You delete the demo CNAME but keep the wildcard You rely on wildcard ALIAS to “cover” GitHub Pages (it won’t) Recommendation (practical) ✔️ Yes, use demo.yseeku.com for GitHub Pages ✔️ Keep the explicit demo CNAME ✔️ Configure the domain inside GitHub Pages ❌ Don’t let Vercel know about it If you want, tell me: Which repo backs demo Whether docs should also be GitHub Pages I’ll give you the exact final DNS + GitHub Pages config to lock it in cleanly.