--- title: "FastChat vs CTranslate2" type: "comparison" canonical_url: "https://www.graphcanon.com/compare/lm-sys-fastchat-vs-opennmt-ctranslate2" tools: ["lm-sys-fastchat", "opennmt-ctranslate2"] --- # FastChat vs CTranslate2 *GraphCanon updated Jul 12, 2026* ## Verdict Pick FastChat when fastChat is primarily Python; CTranslate2 is C++; pick CTranslate2 when cTranslate2 is primarily C++; FastChat is Python. [FastChat](https://github.com/lm-sys/FastChat) reports 39k GitHub stars, 4.8k forks, and 1.0k open issues, last pushed May 1, 2026. [CTranslate2](https://opennmt.net/CTranslate2) has 4.6k stars, 498 forks, and 271 open issues, last pushed Jul 3, 2026. Figures are from public GitHub metadata via [FastChat's repository](https://github.com/lm-sys/FastChat) and [CTranslate2's repository](https://github.com/OpenNMT/CTranslate2). | | [FastChat](/tools/lm-sys-fastchat.md) | [CTranslate2](/tools/opennmt-ctranslate2.md) | | --- | --- | --- | | Tagline | An open platform for training, serving, and evaluating large language models | Fast inference engine for Transformer models | | Stars | 39,490 | 4,566 | | Forks | 4,788 | 498 | | Open issues | 1,027 | 271 | | Language | Python | C++ | | Adopt for | FastChat is a comprehensive open platform for managing large language models (LLMs) that includes capabilities for training, serving, evaluating, and comparing chatbot models via web UIs and RESTful APIs. It powers ChatB | - | | Persona | - | - | | Runtime | - | - | | License | Apache-2.0 | MIT | | Categories | LLM Frameworks, Model Training, Inference & Serving, Evaluation & Observability | Inference & Serving | ## Trust and health _Sourced signals - not a safety guarantee. No winner column._ | | [FastChat](/tools/lm-sys-fastchat.md) | [CTranslate2](/tools/opennmt-ctranslate2.md) | | --- | --- | --- | | Maintenance | Steady (60%) | Active (82%) | | Days since push | 71d | 8d | | Open issues (now) | 1.0k | 271 | | Full report | [trust report](/tools/lm-sys-fastchat/trust.md) | [trust report](/tools/opennmt-ctranslate2/trust.md) | ## Shared compatibility - **Python**: [FastChat](/tools/lm-sys-fastchat.md) - Python runtime; [CTranslate2](/tools/opennmt-ctranslate2.md) - Python runtime ## Decision facts: FastChat - **Adopt for:** FastChat is a comprehensive open platform for managing large language models (LLMs) that includes capabilities for training, serving, evaluating, and comparing chatbot models via web UIs and RESTful APIs. It powers ChatB ## Choose when ### Choose FastChat if… - FastChat is primarily Python; CTranslate2 is C++. - License: FastChat is Apache-2.0, CTranslate2 is MIT. - Tags unique to FastChat: evaluation system, large-language-models, chatbots, distributed serving. - Also covers LLM Frameworks, Model Training, Evaluation & Observability. - - You are looking to train and evaluate state-of-the-art models such as Vicuna or MT-Bench. ### Choose CTranslate2 if… - CTranslate2 is primarily C++; FastChat is Python. - License: CTranslate2 is MIT, FastChat is Apache-2.0. - Tags unique to CTranslate2: avx, deep-learning, cpp, cuda. ## When NOT to use FastChat - - You require a proprietary or closed-source framework; FastChat is open-source under Apache-2.0 license and its use might be unsuitable for environments requiring proprietary solutions. - - Your chatbot evaluation needs do not align with the types of data used in FastChat's datasets (e.g., human votes, MT-Bench evaluations). - - You prefer a more user-friendly setup without the need to clone a repository and manually install dependencies; FastChat requires installation from source with additional steps for Rust and CMake on - + Mac. ## When NOT to use CTranslate2 - Inference & Serving: Self-hosting rarely beats a hosted API on cost until you have steady, high-volume traffic. ## Common questions ### What is the difference between FastChat and CTranslate2? FastChat: An open platform for training, serving, and evaluating large language models. CTranslate2: Fast inference engine for Transformer models. See the comparison table for live GitHub stats and shared categories. ### When should I choose FastChat over CTranslate2? Choose FastChat over CTranslate2 when FastChat is primarily Python; CTranslate2 is C++; License: FastChat is Apache-2.0, CTranslate2 is MIT; Tags unique to FastChat: evaluation system, large-language-models, chatbots, distributed serving; Also covers LLM Frameworks, Model Training, Evaluation & Observability; - You are looking to train and evaluate state-of-the-art models such as Vicuna or MT-Bench. ### When should I choose CTranslate2 over FastChat? Choose CTranslate2 over FastChat when CTranslate2 is primarily C++; FastChat is Python; License: CTranslate2 is MIT, FastChat is Apache-2.0; Tags unique to CTranslate2: avx, deep-learning, cpp, cuda. ### When should I avoid FastChat? - You require a proprietary or closed-source framework; FastChat is open-source under Apache-2.0 license and its use might be unsuitable for environments requiring proprietary solutions. - Your chatbot evaluation needs do not align with the types of data used in FastChat's datasets (e.g., human votes, MT-Bench evaluations). - You prefer a more user-friendly setup without the need to clone a repository and manually install dependencies; FastChat requires installation from source with additional steps for Rust and CMake on + Mac. ### When should I avoid CTranslate2? Inference & Serving: Self-hosting rarely beats a hosted API on cost until you have steady, high-volume traffic. ### Is FastChat or CTranslate2 more popular on GitHub? FastChat has more GitHub stars (39,490 vs 4,566). Stars measure visibility, not whether either tool fits your constraints. ### Are FastChat and CTranslate2 open source? Yes - both are open-source projects on GitHub (FastChat: Apache-2.0, CTranslate2: MIT). ### Where can I find alternatives to FastChat or CTranslate2? GraphCanon lists graph-backed alternatives at [FastChat alternatives](/tools/lm-sys-fastchat/alternatives) and [CTranslate2 alternatives](/tools/opennmt-ctranslate2/alternatives) ([FastChat markdown twin](/tools/lm-sys-fastchat/alternatives.md), [CTranslate2 markdown twin](/tools/opennmt-ctranslate2/alternatives.md)), ranked by typed relationship edges rather than popularity votes. ### Is there a machine-readable version of this comparison? Yes. The markdown twin at [this comparison](/compare/lm-sys-fastchat-vs-opennmt-ctranslate2.md) mirrors this page for agents and LLM crawlers, with the same stats table and FAQ answers. ### Which is better maintained, FastChat or CTranslate2? FastChat: Steady. CTranslate2: Active. Compare maintenance labels, days since push, and release cadence in the trust section below - stars alone do not measure maintenance. ### Where are the full trust reports for FastChat and CTranslate2? GraphCanon publishes per-repo trust reports with dated maintenance, provenance, and scan summaries: [FastChat trust report](/tools/lm-sys-fastchat/trust); [CTranslate2 trust report](/tools/opennmt-ctranslate2/trust). --- **Machine-readable endpoints** - JSON: [`/api/graphcanon/graph?tool=lm-sys-fastchat`](/api/graphcanon/graph?tool=lm-sys-fastchat) - LLM index: [/llms.txt](/llms.txt) - Full corpus: [/llms-full.txt](/llms-full.txt) _GraphCanon - The knowledge graph for AI development. https://www.graphcanon.com/_