SSLHandshakeException: PKIX path building failed

What the log looks like

javax\.net\.ssl\.SSLHandshakeException: sun\.security\.validator\.ValidatorException: PKIX path building failed: sun\.security\.provider\.certpath\.SunCertPathBuilderException: unable to find valid certification path to requested target
sun\.security\.provider\.certpath\.SunCertPathBuilderException: unable to find valid certification path to requested target

How to fix it

1. Install an up-to-date Java runtime (such as Adoptium Temurin Java 8u400+ for Minecraft 1.16.5 and older, or Java 17/21 for newer versions) and point your launcher or instance settings to the new Java executable instead of bundled 1.8.0_51.
2. If you use Prism Launcher with legacy Minecraft versions, close the game, click Folders > Java in the main launcher toolbar, delete the jre-legacy folder, and launch the instance again so it fetches an updated Java build.
3. Verify that your Windows, macOS, or Linux date, time, and time zone are set to sync automatically, because an inaccurate system clock causes valid SSL certificates to fail verification.
4. Disable HTTPS scanning, SSL inspection, or Encrypted Web Scan features in third-party antivirus suites (such as Avast, AVG, Kaspersky, ESET, or Bitdefender), as Java does not trust local antivirus root certificates by default.
5. Disconnect from VPNs, custom proxies, or school/work Wi-Fi networks that filter encrypted web traffic, then test logging in or launching the game again.

Check your own log