Fish Audio: S2.1 Pro Free (free)

Fish Audio: S2.1 Pro Free is a speech synthesis model from Fish Audio, offered as the no-cost variant of Fish Audio S2.1 Pro. It is intended for testing, prototyping, and low-volume applications, and it provides the same synthesis capabilities as the paid model without production latency or availability guarantees. If you are evaluating Fish Audio's speech technology or building something small, this is the version to start with.

The model takes text as its only input and produces speech as its only output. That makes it a straightforward text-to-speech system: you send text, you get audio back. No context length is published for this model, and the maximum output is listed as zero, so there is no documented token budget to plan around. The supported parameters list is empty, which means the request surface is minimal and you should not expect to tune generation through the usual sampling or formatting knobs.

The practical uses follow directly from that shape. Prototyping a voice interface, generating placeholder audio for a demo, testing how a script sounds before committing to a production voice, or adding speech to a low-volume internal tool are all reasonable fits. Because the model is text in and speech out, it suits any workflow where you already have written content and need it spoken. It is less suited to tasks that need audio understanding, since it does not accept audio as input.

You call it through api14's OpenAI-compatible API using the model id "fish-audio/s2.1-pro-free:free". Because the API follows the OpenAI format, you point your existing client at api14's base URL and pass that model id in your request, with the text you want spoken as the input. The model supports no additional request parameters, so keep your payload simple and rely on the defaults rather than passing temperature, top_p, or similar fields.

The main caveat is the free tier itself. Fish Audio describes this variant as lacking production latency or availability, so it is not the right choice for user-facing products where response time and uptime matter. If you need those guarantees, the paid S2.1 Pro is the natural step up. For everything else, this model gives you the same synthesis capabilities at no cost, which makes it a sensible first stop for experiments and small workloads.