The **Really Simple SSL Pro** WordPress plugin helps secure your website by automatically configuring it to use HTTPS, resolving issues related to mixed content, and handling redirects from HTTP to HTTPS. Key features include:

1. **Automatic HTTPS Setup**: It detects SSL certificates and forces all content to load over HTTPS.
2. **Mixed Content Fixer**: The Pro version ensures that mixed content (elements still using HTTP) is fixed across the entire site, which is especially useful for avoiding browser security warnings.
3. **Security Enhancements**: It implements **HTTP Strict Transport Security (HSTS)**, ensuring all visitors are served the HTTPS version of your site, and can alert you before SSL certificates expire.
4. **Easy Installation**: Both versions are easy to set up, allowing you to activate SSL with minimal steps【27†source】【28†source】.
5. **Premium Support**: Pro users get responsive email support for any troubleshooting needs【28†source】.

The plugin is lightweight, but users need to keep it active to maintain SSL fixes. There may be a slight performance impact, though it’s generally minimal【29†source】.

If you’re looking to secure a WordPress site and avoid SSL-related errors, Really Simple SSL Pro is a solid option.