Simli is a focused real-time avatar API for teams that already have—or plan to build—a voice agent. It converts live audio into a synchronized talking-face video stream and supports LiveKit, Pipecat, WebRTC, and SDK integrations. It is a strong composable option, but buyers must budget the separate speech, model, transport, and operational layers around it.
Last verified: September 17, 2026. Simli can change its API, free allowance, plan terms, and supported integrations; verify the current dashboard and documentation before launch.
What is Simli AI?
Simli describes its core product as a speech-to-video API. Your application sends audio; Simli generates a lip-synchronized avatar stream for the user. The core product should not automatically be treated as speech recognition, an LLM, text-to-speech, business logic, and an avatar in one price.
This narrower scope can be an advantage. A team can keep its existing voice agent, retrieval system, tools, permissions, and observability, then attach a face at the output. It also means a fair cost and latency comparison must include the entire agent stack rather than comparing one Simli minute with a bundled platform minute.
How does the Simli avatar API work?
The current developer overview presents LiveKit, Pipecat, and Simli SDKs as primary integration paths. For custom WebRTC clients, the application creates a session, sends supported audio, and receives real-time video.
Simli’s API migration guide is especially important for older tutorials. It documents the current WebRTC and LiveKit paths and notes that the old text-to-video endpoint was removed. Developers should now generate speech through their chosen voice service and send audio to Simli. Copying an older text-input example can therefore produce unnecessary migration work.
Simli publishes a speech-to-video latency figure below 300 milliseconds on its website. That is a vendor claim for Simli’s stage of the pipeline, not an end-to-end promise. The user’s perceived response also includes turn detection, transcription, model generation, tools, speech synthesis, transport, buffering, and playback.
| Integration layer | Simli supplies | Product-team responsibility |
|---|---|---|
| Avatar generation | Lip-synchronized speech-to-video output | Choose the face, rights, and visual acceptance criteria |
| Audio input | Audio-driven real-time session | Generate and format speech from the selected voice stack |
| Media delivery | WebRTC and framework integration paths | Handle session lifecycle, reconnects, and UI states |
| Agent intelligence | Not necessarily included in the core API | Own STT, model, tools, retrieval, policy, and observability |
LiveKit, Pipecat, and other integrations
The official LiveKit Simli plugin lets a Python LiveKit agent attach a Simli face to its audio output. This is a practical path when a team already uses LiveKit for real-time rooms and agent sessions.
Pipecat also documents a Simli video service for WebRTC avatar output. Simli’s sample index links examples for OpenAI Realtime, Pipecat, Vapi, and other combinations. Confirm that an example targets the current API before using it as a production template; some older ElevenLabs material is marked deprecated.
These integrations make Simli useful as a visible endpoint for a voice agent. They do not eliminate the need to design interruption, idle-session cleanup, reconnect behavior, transcript handling, and safeguards around tool use.
How much does Simli cost?
Simli’s public website currently advertises a $10 signup credit and a monthly top-up of 50 minutes. It describes paid access as flexible pay-as-you-go billing with volume discounts, but it does not expose a complete, stable paid rate card for every account on the public page.
That makes exact third-party per-minute estimates unsuitable for procurement. Use the dashboard or a written quote to confirm the effective rate, overages, custom-face costs, concurrency, maximum session duration, support, and SLA. The dedicated Simli pricing guide explains how to model the full cost without treating directory estimates as official prices.
| Cost component | Included in the public Simli description? | What to verify |
|---|---|---|
| Speech-to-video avatar | Yes | Effective minute rate, overage, and session billing boundary |
| Speech recognition | Not necessarily | Provider and streaming cost |
| LLM or speech-to-speech model | Not necessarily | Model, tokens, tools, and caching |
| Text-to-speech | Needed for audio-driven paths | Voice provider and audio format |
| Real-time transport | Integration-dependent | LiveKit or other media cost |
| Custom face and support | Terms vary | Quota, rights, turnaround, and SLA |
Simli strengths and limitations
Simli’s strongest fit is a developer team that wants a focused visual layer without surrendering the agent’s intelligence. LiveKit and Pipecat support reduce the amount of custom media plumbing, and an audio-driven interface makes it compatible with multiple model and voice providers.
The same composability creates operational responsibility. Your team still owns the surrounding AI pipeline and must debug boundaries between services. Cloud-generated video also introduces continuous media delivery and client decoding. Public pricing is sufficient for starting a prototype, but not for approving a production budget without account-level terms.
Simli versus Spatius
Both products can sit after an existing voice agent, but they deliver the avatar differently.
| Decision area | Simli | Spatius |
|---|---|---|
| Core role | Speech-to-video avatar service | Client-rendered avatar layer |
| Output | Cloud-generated real-time video | Compact control data rendered by the client SDK |
| Existing AI stack | Can remain in place | Remains in place |
| Common integration focus | LiveKit, Pipecat, WebRTC, and audio formats | Web, iOS, Android, and existing-agent integration |
| Main production tests | Video latency, bandwidth, session limits, and concurrency | Device performance, motion delivery, SDK behavior, and stack control |
Choose Simli when a cloud speech-to-video stream fits the product and the available integrations shorten development. Evaluate Spatius when client-side rendering, native-device delivery, or separation from continuous cloud video is important. The Spatius LiveKit integration shows how a client-rendered visual layer can remain separate from the LiveKit agent.
For cost planning, compare the complete workloads using the real-time AI avatar API pricing guide rather than treating cloud-video and client-rendered minutes as equivalent.
What should buyers test in a Simli pilot?
Start with the target production stack, not a standalone avatar demo. Measure the time from the user’s end of speech to audio playback, then measure the additional time to synchronized video. Test barge-in, long answers, silence, reconnection, packet loss, mobile networks, and the maximum expected concurrent sessions.
Record total cost per completed conversation, including abandoned and idle sessions. Confirm who owns avatar consent, generated media, logs, and custom-face assets. Finally, review fallback behavior: the agent should still explain an error or continue in audio-only mode if the visual service becomes unavailable. The avatar SDK testing guide provides a reusable acceptance plan.
Simli AI FAQ
Is Simli an AI agent platform?
Simli’s core offering is a speech-to-video avatar API. It can connect to agent frameworks and model providers, but buyers should not assume the avatar minute includes every conversational component.
Is Simli free?
Simli currently advertises a $10 signup credit and a monthly 50-minute top-up. Verify current usage rights, limits, and paid terms in the account before launch.
Does Simli work with LiveKit?
Yes. LiveKit documents a Python avatar plugin for Simli. Use it to connect a LiveKit agent’s audio output to a Simli face and test the full end-to-end pipeline.
Does Simli support Pipecat and Vapi?
Pipecat documents a Simli video service, and Simli links sample integrations for Pipecat and Vapi. Check each sample against the current API because older examples may be deprecated.
When should a team compare Simli with Spatius?
Compare them when an existing voice agent needs a visual layer. Simli returns cloud-generated video; Spatius renders the avatar in the client. Test both with the same device, network, workload, and cost model.
Choose the visual layer around the agent you already own
Simli is credible for developers who want a real-time face attached to a composable voice stack. The final decision should come from a production-shaped pilot, not a single latency claim or directory price.
Compare a client-rendered avatar layer with your current LiveKit, voice, or agent architecture. Request a demo, or ，或Review Spatius pricing.。