static public String slf4jVersion() {
//        String moduleVersion = slf4jVersionByModule();
//        if(moduleVersion != null)
//            return moduleVersion;

        Package pkg = Slf4jEnvUtil.class.getPackage();
        if(pkg == null) {
            return null;
        }
        final String pkgVersion = pkg.getImplementationVersion();
        return pkgVersion;
    }
Returns the current version of slf4j, or null if data is not available.

@return current version or null if missing version data
@since 2.0.14
slf4j-api/src/main/java/org/slf4j/helpers/Slf4jEnvUtil.java