What are some alternatives?
When comparing Smartling and Crowdin, you can also consider the following products
Transifex - Transifex makes it easy to collect, translate and deliver digital content, web and mobile apps in multiple languages. Localization for agile teams.
POEditor - The translation and localization management platform that's easy to use *and* affordable!
Lokalise - Localization tool for software developers. Web-based collaborative multi-platform editor, API/CLI, numerous plugins, iOS and Android SDK.
OneSky - Full Stack Localization Solution
Localize - Localize is translation software that automatically converts the content of your website or app into multiple languages.
Weblate - Weblate is a free web-based translation management system.