12 unstable releases (4 breaking)

0.11.0 Feb 9, 2021
0.10.0 Sep 25, 2020
0.9.3 Mar 4, 2020
0.9.1 Nov 26, 2019
0.1.0 Jul 29, 2018

#332 in Internationalization (i18n)

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Used in 183 crates (20 directly)


1.5K SLoC

Fluent Syntax

fluent-syntax is a parser/serializer API for the Fluent Syntax, part of the Project Fluent, a localization framework designed to unleash the entire expressive power of natural language translations.

crates.io Build and test Coverage Status


The crate currently provides just a parser, which is tracking Fluent Syntax on its way to 1.0.

Local Development

cargo build
cargo test
cargo bench

When submitting a PR please use cargo fmt (nightly).

Learn the FTL syntax

FTL is a localization file format used for describing translation resources. FTL stands for Fluent Translation List.

FTL is designed to be simple to read, but at the same time allows to represent complex concepts from natural languages like gender, plurals, conjugations, and others.

hello-user = Hello, { $username }!

Read the Fluent Syntax Guide in order to learn more about the syntax. If you're a tool author you may be interested in the formal EBNF grammar.

Get Involved

fluent-rs is open-source, licensed under the Apache License, Version 2.0. We encourage everyone to take a look at our code and we'll listen to your feedback.


We'd love to hear your thoughts on Project Fluent! Whether you're a localizer looking for a better way to express yourself in your language, or a developer trying to make your app localizable and multilingual, or a hacker looking for a project to contribute to, please do get in touch on discourse and the IRC channel.


~22K SLoC