babel is a tool similar to l10n. It’s more low-level but supports HTML and JS files.
weblate is a WebUI for continious translation.
translate is a CLI tool for different operations on po and mo files, like converting in different formats or showing statistics.
polib is a pure Python tool to work with po files. In case you want to collect some information that isn’t covered by tools provided by
i18next is a JS library for translating frontend.