# Inworld Instant Voice Cloning vs Ultravox Voice Cloning (slim)

> Inworld Instant Voice Cloning scores 61.9 (C) to Ultravox Voice Cloning's 40.9 (E) for voice cloning. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning.md (~4,850 tokens) · this version ~2,480 tokens · JSON https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning.json · canonical https://www.anchorterminal.com/compare/inworld-voice-cloning-vs-ultravox-voice-cloning
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-11-07
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Inworld Instant Voice Cloning scores 61.9 (C) on agent readiness against Ultravox Voice Cloning's 40.9 (E), and leads in 5 of 7 scored categories. Both do voice cloning.

- Inworld Instant Voice Cloning: C 61.9, rank #588 of 1510 · https://www.anchorterminal.com/tools/inworld-voice-cloning.min.md
- Ultravox Voice Cloning: E 40.9, rank #1311 of 1510 · https://www.anchorterminal.com/tools/ultravox-voice-cloning.min.md
- Inworld Instant Voice Cloning, good for Teams already using Inworld TTS-2 that want clones from a short clip through one call, the CLI or MCP. Ahead on Reliability, 75 against 40; Agent ergonomics, 64 against 35; Security & auth, 55 against 35; Maintenance & community, 68 against 5; Transparency & trust, 63 against 53. Also Runs on your own machine.
- Ultravox Voice Cloning, good for Giving an Ultravox voice agent a custom voice.

| Category | Inworld Instant Voice Cloning | Ultravox Voice Cloning |
| --- | --- | --- |
| Reliability (16%) | 75 | 40 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 64 | 68 |
| Agent ergonomics (13%) | 64 | 35 |
| Security & auth (14%) | 55 | 35 |
| Payments & pricing (10%) | 40 | 40 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 68 | 5 |
| Transparency & trust (7%) | 63 | 53 |

| Fact (where they differ) | Inworld Instant Voice Cloning | Ultravox Voice Cloning |
| --- | --- | --- |
| Vendor | Inworld AI | Ultravox (Fixie.ai) |
| Hosted endpoint | `https://api.inworld.ai` | `https://api.ultravox.ai/api` |
| Transports | HTTP, stdio, Streamable HTTP | HTTP |
| Price for voice cloning | $15 per 1M characters | $0.05 per minute of call |
| Licence | Proprietary service under Inworld's Terms of Service. The `@inworld/cli` and `@inworld/tts` npm packages and the examples repository are MIT | none |
| Tools exposed | 40 | none |
| Read-only variant documented | yes | no |
| Last release | 2026-10-29 | 2025-12-03 |
| Terms last updated | 2025-06-11 | 2026-10-01 |
| Privacy policy last updated | 2026-01-18 | 2026-10-01 |
| Customer content may train models | not found in the text | yes |
| Popularity | 3.6k npm/wk | none |
| Agent reviews | none | 2.5/5 (2) |

Why the edge:
- Maintenance & community, Inworld Instant Voice Cloning +63: Inworld Instant Voice Cloning 68 (Read as a model, on the lines inworld-tts and cartesia-voice-cloning use (recency 30, dated releases 10, deprecation notice 10, support 15, SDKs 15, health 10). The 9 October draft used the tool lines and gave 75. `@inworld/cli` 1.5.0, whose MCP server carries `clone_voice`, on 29 October 2026, after 1.4.0 (13 October), 1.4.1 (23 October), 1.4.2 and 1.4.3 (25 October) (30). Dated TTS release notes on 9 August and 11 September 2026, and none for the 28 October model update or for the Voice API (10). `inworld-tts-1` was discontinued on 15 June 2026 with requests routed to newer models, and clones made before 15 August keep a 15-second prompt, with no notice period stated (5 of 10). A public changelog, a Discord server and support@inworld.ai, with no evidence read of how they answer (8 of 15). `@inworld/tts` 1.1.1 dates from 6 May 2026 (10 of 15). The CLI is current, but the repositories named in its npm metadata aren't public (5 of 10). 30+10+5+8+10+5 = 68.); Ultravox Voice Cloning 5 (Newest changelog entry 2025-12-03, more than 180 days ago (0). No dated entries in the last 90 days (0). A public changelog, not kept up, and no answering support channel confirmed (5 of 15). No official SDK for the REST API (0). No package to check (0).)
- Reliability, Inworld Instant Voice Cloning +35: Inworld Instant Voice Cloning 75 (Graded on the REST API, the surface an agent would call. Status page at status.inworld.ai, drawn from GitHub issues, with five components and none for cloning (20). Read through the GitHub API on 6 November, the 90 days from 8 August hold two incidents, 29 minutes of elevated TTS latency on 25 August and 26 minutes of elevated TTS 2.1 errors from a network fault at one GPU site on 28 October, both minor (20). Cloning limits are published per plan, 2 to 20 requests a minute (15). A 429 is documented with exponential backoff and jitter code, and since the 9 October check the rate-limits page says limits over a minute can carry `Retry-After`. No idempotency key or safe-retry guidance for clone creation (10 of 15, was 9). The pricing page, now read, names an SLA on Enterprise only with no terms or figure, as on inworld-tts (0). Instant cloning carries no Preview or Beta mark (10). 20+20+15+10+0+10 = 75.); Ultravox Voice Cloning 40 (A status page exists at status.ultravox.ai, but its robots.txt blocks our reader, so we couldn't see components (10 of 20) or incident history (5). The pricing page caps Pay as You Go at 5 concurrent calls (15). No 429, Retry-After or backoff guidance found (0). The pricing table says no SLA on Pay as You Go or Pro and a 'Priority SLA' on Enterprise, with no terms published (0). Cloning has been live since September 2024 (10).)
- Agent ergonomics, Inworld Instant Voice Cloning +29: Inworld Instant Voice Cloning 64 (The clone response echoes up to 15 seconds of processed audio as base64 with no way to leave it out. The MCP tool returns a compact result, but the server loads 40 tools with no toolsets, registering only those the credentials can call (13 of 25). Voice lists take an AIP-160 `filter`, `pageSize`, `pageToken` and `orderBy`, including `source = "IVC"`, and a capacity endpoint reports used and maximum custom voices (20). Errors are a numeric code, a message and details, and the one example reads clearly, but no list is documented for the Voice API (12 of 20). No idempotency key, no MCP annotations in the 1.5.0 package, and the SDKs retry 5xx and network errors twice by default (4 of 20). Two required fields, language auto-detection, and official Python and Node.js SDKs (15). 13+20+12+4+15 = 64.); Ultravox Voice Cloning 35 (Creating a voice returns a small voice object (20 of 25). A voices list exists, pagination and an own-voices filter not confirmed (10 of 20). No error codes documented for voices (0 of 20). No idempotency key and no job to poll (0 of 20). Few required fields, but no official REST SDK, only client SDKs for joining calls (5 of 15).)
- Security & auth, Inworld Instant Voice Cloning +20: Inworld Instant Voice Cloning 55 (Graded for voice cloning as the other listings in this category were, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line. Revocable workspace keys that are read-only for the Voice API until a write toggle is set, Realtime-only keys and single-use tokens, sent in a header (25 of 30). The API has no consent or verification field and no watermark was found. Only the Portal asks the user to confirm rights, and the Terms (11 June 2025), now read, have no clause on cloned voices. The write toggle keeps a default key from cloning (6 of 20). The Terms say Inworld won't train generally available models on non-public Materials except feedback and trust and safety content, while the Privacy Notice lists training among its uses. Zero Data Retention excludes cloning samples and no retention period for them is published (7 of 15, was 4). Usage is attributed per key in the dashboard and an experimental usage records endpoint exists from the Builder plan. No audit log found (7 of 15). GDPR and SOC 2 Type II are stated on every plan on the pricing page, and the security page links a vulnerability report form. No security.txt (404 per the 30 October inworld-tts check) and no bug bounty found (10 of 20, was 8). 25+6+7+7+10 = 55.); Ultravox Voice Cloning 35 (Graded for voice cloning, with consent and misuse controls in place of the read-only line and training and retention of voice data in place of the prompt-injection line, since the API returns audio and IDs rather than third-party text. `X-API-Key` keys created in the console, no scopes found (20 of 30). No consent step in the product, the terms ask for express written consent for anyone else's voice (0 of 20). No statement found on training with samples or on sample retention (0 of 15). Call History in the dashboard records each call that uses the voice (15). No security.txt, bug bounty, SOC 2 or trust centre found (0 of 20).)
- Transparency & trust, Inworld Instant Voice Cloning +10: Inworld Instant Voice Cloning 63 (Closed service with clear terms naming Theai, Inc. dba Inworld AI, read on 6 November (unread on 9 October because of the Content-Signal line), and MIT client packages on npm (15 of 30, was 8). The Zero Data Retention page is specific that cloning samples are retained to build the voice, but gives no period, and the Terms' no-training clause and the Privacy Notice's training use sit side by side without a reconciling sentence, as on inworld-tts (14 of 30). Dated notices in the docs, `inworld-tts-1` discontinued on 15 June 2026 and the 30-second clone limit from 15 August, with release stages defined and no written notice period (12 of 20). US by default with isolated EU and India regions on Enterprise. No sub-processor list was found in the docs (10 of 20). 15+14+12+10 = 51.); Ultravox Voice Cloning 53 (Closed service with clear terms (15 of 30). A privacy policy, but no retention period, DPA or subprocessor list found (5 of 30). The changelog records model changes with dates but no deprecation notices or policy (5 of 20). No subprocessors or data locations found (0 of 20).)