IndexTTS-2.5

IndexTTS-2.5 is a zero-shot text-to-speech model that performs voice cloning from a single reference audio. It supports Chinese, English, Japanese, Spanish, and Arabic, with cross-lingual voice transfer and disentangled emotion control.

Compared to IndexTTS-2, it adds Japanese/Spanish/Arabic support, improves inference speed, and enhances controllability of Chinese Pinyin, English CMU phonemes, and Japanese Kana.

Model Details

• Developed by: IndexTeam, Bilibili
• Model type: Autoregressive zero-shot TTS (GPT + DiT + BigVGAN)
• Languages: Chinese, English, Japanese, Spanish, Arabic
• License: Bilibili Model License

Model Sources

• Repository: github.com/index-tts/index-tts
• Demo: IndexTTS-2.5 Demo Page

How to Get Started

Installation

git clone https://github.com/index-tts/index-tts.git && cd index-tts
git lfs pull
pip install -U uv
uv sync --all-extras

Download Model Weights

# HuggingFace
uv tool install "huggingface-hub[cli,hf_xet]"
hf download IndexTeam/IndexTTS-2.5 --local-dir=checkpoints

# ModelScope
uv tool install "modelscope"
modelscope download --model IndexTeam/IndexTTS-2.5 --local_dir checkpoints

Quick Inference

from indextts.infer_v2_5 import IndexTTS2

tts = IndexTTS2(cfg_path="checkpoints/config.yaml", model_dir="checkpoints", use_bf16=True)

# Basic voice cloning
tts.infer(
    spk_audio_prompt="prompt.wav",
    text="Hello, this is a voice cloning demo.",
    lang="EN",
    output_path="output.wav",
)

# With emotion control
tts.infer(
    spk_audio_prompt="prompt.wav",
    text="快躲起来！是他要来了！",
    lang="ZH",
    output_path="output.wav",
    emo_vector=[0, 0, 0.8, 0, 0, 0, 0, 0],
)

# With Pinyin/phoneme annotation
tts.infer(
    spk_audio_prompt="prompt.wav",
    text="他在银<行|XING2>里<行|HANG2>走了半天。",
    lang="ZH",
    output_path="output.wav",
)

Web Demo

uv run webui.py --version 2.5 --model_dir ./checkpoints

Uses

Direct Use

• Zero-shot voice cloning from a single reference audio
• Multilingual speech synthesis (Chinese, English, Japanese, Spanish, Arabic)
• Cross-lingual voice transfer (e.g., Chinese speaker voice → English output)
• Emotion-controllable speech synthesis via emotion vectors, emotion reference audio, or text-based emotion detection

Downstream Use

• Audiobook and podcast production
• Voice dubbing and localization
• Conversational AI and virtual assistants

Out-of-Scope Use

• Impersonation or deception without consent
• Generating misleading or fraudulent audio content
• Any use that violates applicable laws or regulations

Bias, Risks, and Limitations

• Voice cloning quality may vary across speakers and languages.
• The model may produce artifacts or unnatural prosody for very long or highly complex text.
• Cross-lingual transfer quality depends on the target language and speaker characteristics.
• The model does not verify speaker identity or consent. Users are responsible for ethical use.

Evaluation

Zero-Shot TTS (CV3-Eval)

Model	Params	zh WER↓	zh SS↑	en WER↓	en SS↑	es WER↓	es SS↑	ja WER↓	ja SS↑	ar WER↓	ar SS↑
VoxCPM2	2B	3.88	74.99	5.13	71.57	5.49	74.67	6.69	72.90	14.94	65.99
CosyVoice3-0.5B	0.5B	3.84	80.01	4.88	74.16	4.04	78.85	-	76.36	-	-
Fish Audio S2 Pro	4B	3.62	67.79	3.83	61.66	2.93	67.44	5.15	66.15	14.15	59.43
Qwen3-TTS	1.7B	3.27	73.02	5.06	67.17	2.87	73.17	5.89	70.18	-	-
IndexTTS2.5	0.8B	4.36	77.10	5.12	68.06	3.75	76.39	5.66	74.62	14.88	69.74
IndexTTS2.5-RL	0.8B	3.93	77.92	3.89	67.79	3.33	76.68	5.30	75.41	13.58	70.36

Cross-Lingual TTS (Chinese prompt → target language)

Model	Params	zh→en WER↓	zh→en SS↑	zh→es WER↓	zh→es SS↑	zh→ja WER↓	zh→ja SS↑	zh→ar WER↓	zh→ar SS↑
VoxCPM2	2B	4.48	64.25	16.38	64.89	11.84	71.54	11.09	67.62
CosyVoice3-0.5B	0.5B	3.23	62.79	4.58	64.04	-	-	-	-
IndexTTS2.5	0.8B	3.62	63.83	5.17	65.48	6.57	74.16	9.51	71.02
IndexTTS2.5-RL	0.8B	3.55	67.47	4.86	64.47	6.38	75.82	9.89	73.05