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Fish Audio

S2.1 Pro

S2.1 Pro is Fish Audio's recommended production text-to-speech model, covering 83 languages with natural language prosody control and two-speaker dialogue in a single request. Your use is subject to Fish Audio's Terms & Privacy Policies.

Free
Use with AI GatewayView docs
import { experimental_generateSpeech as generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';


const result = await generateSpeech({
  model: gateway.speechModel('fish-audio/s2.1-pro'),
  text: 'Hello from the Vercel AI Gateway!',
  // Browse voices at https://fish.audio/app/discovery
  // Open a voice, then use "Copy Model Id" in its "..." menu.
  voice: '933563129e564b19a115bedd57b7406a',
});


await writeFile('speech.mp3', result.audio.uint8Array);
Read docs
OverviewAboutProvidersSimilarFAQ

Copy link to headingPlayground

Try out S2.1 Pro by Fish Audio. Usage is billed to your team at API rates. Free users (those who haven't made a payment) get $5 of credits every 30 days.

fish-audio logo
Text
The text the model will read aloud.
Voice
fish-audio logo

Your generated audio will appear here

Copy link to headingProviders

Route requests across multiple providers. Copy a provider slug to set your preference. Visit the docs for more info. Using a provider means you agree to their terms, listed under Legal.

Provider
Input
Capabilities
ZDR
No Training
Release Date
Fish Audio
Free
Legal:Terms•Privacy
Free
07/28/2026

Copy link to headingMore models by Fish Audio

Model
Context
Latency
Throughput
Input
Output
Cache
Web Search
Capabilities
Providers
ZDR
No Training
Release Date
fish-audio/s2-pro
Free
Free
—
fish-audio logo
03/09/2026
fish-audio/transcribe-1
Free
Free
—
fish-audio logo
03/01/2026
fish-audio/s1
Free
Free
—
fish-audio logo
10/20/2025

Copy link to headingAbout S2.1 Pro

S2.1 Pro is Fish Audio's recommended production text-to-speech model and an improved version of S2 Pro, with better quality, latency, and throughput across 83 languages.

Prosody control is the distinguishing feature. You write direction inline in square brackets, and the model interprets it as description rather than matching against a fixed vocabulary, so [whispers sweetly] and [laughing nervously] both work without either being a predefined tag. Thousands of distinct tags are recognised, and phrasing outside that set still lands because the model learned the mapping from description to acoustics rather than from a lookup table.

Multi-speaker dialogue runs in a single request. You write both sides of a conversation in one text input, tag each turn with a speaker index, and get back one audio file with both voices rendered. Two speakers are supported per request.

In head-to-head listening comparisons against S2 Pro, S2.1 Pro was preferred in roughly three of every five judgements.

Integration uses the AI SDK's speech generation function.

Copy link to headingWhat To Consider When Choosing a Provider

  • Configuration: Dialogue is capped at two speakers per request. A three-way conversation needs separate requests stitched together, which means you handle the timing between turns yourself.
  • Configuration: Fish Audio also publishes a free development tier serving the same model quality and language coverage, without latency or availability guarantees. Use that for evaluation and prototyping, and this model where a production workload needs those guarantees.
  • Configuration: Bracket direction is interpreted, not parsed. That flexibility is the point, but it means the same tag can land slightly differently across generations. Where a specific delivery matters, generate a few takes and pick, rather than assuming one tag produces one fixed result.
  • Zero Data Retention: Zero Data Retention is offered on a per-provider and model basis. See the documentation for details.
  • Authentication: AI Gateway authenticates requests using an API key or OIDC token. You do not need to manage provider credentials directly.

Copy link to headingWhen to Use S2.1 Pro

Best for

  • Production Voice Workloads: Latency and availability guarantees included
  • Multilingual Narration: 83 languages from a single model
  • Expressive Direction: Plain-language control instead of a fixed tag list
  • Two-Speaker Dialogue: One request, one audio file, both voices
  • Upgrades From S2 Pro: Favoured in head-to-head listening comparisons

Consider alternatives when

  • Evaluation And Prototyping: The free development tier serves the same quality
  • Three Or More Speakers: Exceeds the two-speaker per-request cap
  • Open Weights Requirement: S2 Pro is the open-source generation
  • Fixed Emotional Presets: S1 exposes an explicit expression vocabulary

Copy link to headingConclusion

S2.1 Pro is Fish Audio's production voice model, with 83 languages, plain-language prosody direction, and two-speaker dialogue in a single request. Point fish-audio/s2.1-pro at AI Gateway for production traffic, and prototype against the free tier while you are still choosing voices.