The REST API encountered an error 📝 WordPress

Site Health: The REST API encountered an error / Your site could not complete a loopback request (cURL error 28)

WordPress couldn’t call itself over HTTP — needed for the block editor, cron, plugin/theme editors and Site Health.

Seen on: WordPress

Meaning

Loopbacks go from the server to its own public URL. Firewalls, DNS that resolves to an unreachable IP inside the server, basic auth, Cloudflare challenges, or self-signed certificates break them (cURL error 28 timeout, cURL error 6/7/60).

Common causes

  • Server can’t reach its own domain (firewall/NAT hairpin/DNS)
  • Basic authentication on the site
  • Security plugin/WAF blocking server-to-self requests
  • Invalid/self-signed SSL certificate
  • Slow plugin causing timeout

⚡ Quick fix

  1. From the server, curl -I https://yourdomain/wp-json/
  2. Add the domain to /etc/hosts pointing to 127.0.0.1 if NAT hairpin fails
  3. Allow the server IP in WAF/security plugins

Detailed fix by platform

Linux

  1. bash
    curl -sI https://example.com/wp-json/ | head -3
echo "127.0.0.1 example.com www.example.com" | sudo tee -a /etc/hosts

How to diagnose

  1. Reach — curl from the server
  2. Error — cURL error number
  3. Auth — Basic auth enabled?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

🧠 Still stuck? Analyze your error

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