For static websites we usually suggest to start with locizify. It’s optimal for websites, you have the most minimal overhead to instrument your code and it’s even suitable for non developers, too.
For more advanced use-cases and better control through the code instrumentation we suggest i18next. It’s usable on web, mobile, desktop and server environments, has very flexible translations options like, plurals, interpolation, context, etc… and has a big ecosystem (frameworksplugins).
The most low-level integration can be done with our API. Using our API you can build anything you could think of.
As you can see, the answer is “It depends” ;-)
Do not hesitate to contact us for further questions.