Cartesia alternatives

What to consider when choosing a Cartesia alternative (a text-to-speech API platform), built from Cartesia's public pages as of October 10, 2026. ReadAloud, which we make, is one disclosed option among several.

Last verified October 10, 2026.

We make ReadAloud, so it appears below as one of the options, and we say so. Options are listed alphabetically, not ranked.

Who Cartesia suits

We file Cartesia under text-to-speech API platforms: companies whose main product is a speech API that developers call from their own code. It lists a price per character. The audience its pages name: teams building real-time voice agents or multilingual products who want a model Cartesia describes as low-latency, with 44 languages, cloning options and published compliance statements, and who are comfortable with a credit-based subscription.

How Cartesia prices

In Cartesia's words: Monthly subscription that includes a pool of credits (1 credit is about 1 TTS character), with optional per-credit overage billing.

  • Free: Vendor's own unit: 20K credits/month, $0; not converted. Evaluation and personal use; no commercial license listed on the plan card. (source: cartesia.ai)
  • Pro: $50 per 1M characters. Per-1M figure derived by us: $5 per month divided by 100K credits, at about 1 credit per character (the rate Cartesia's docs state). Includes commercial use license and instant voice cloning. Overage $65 per 1M credits if enabled. Applies to Sonic-3.6; the first paid plan with a commercial license. (source: cartesia.ai)
  • Startup: $39.20 per 1M characters. Per-1M figure derived by us: $49 per month divided by 1.25M credits, at about 1 credit per character. Adds professional voice cloning (2 slots). Overage $45 per 1M credits. (source: cartesia.ai)
  • Scale: $37.38 per 1M characters. Per-1M figure derived by us: $299 per month divided by 8M credits (rounded), at about 1 credit per character. 4 PVC slots, priority support, higher concurrency. Overage $38 per 1M credits. (source: cartesia.ai)
  • Enterprise: Vendor's own unit: custom; not converted. Volume pricing; BAAs/DPAs, SSO, custom concurrency. (source: cartesia.ai)

Check whether the listed rate is for the model and latency class you would actually call, and whether concurrency or support tiers cost extra.

Every per-character list price we found for Cartesia, Pro at $50, Startup at $39.20 and Scale at $37.38, is higher than both ReadAloud Live ($4) and ReadAloud Studio ($10) per 1M characters.

Free tier at Cartesia: 20K credits per month (about 20K characters of Sonic TTS), 2 concurrent TTS requests.

What Cartesia lists as strengths

  • Vendor states Sonic delivers first audio in under 90 ms (vendor-stated, not independently verified). (source: cartesia.ai)
  • Sonic 3.6 supports 44 languages from one model. (source: docs.cartesia.ai)
  • Offers instant and professional voice cloning plus an SSML-like tag set for speed, volume and emotion. (source: cartesia.ai)
  • Publishes SOC 2 Type 2, HIPAA-eligibility with BAAs, and GDPR statements, with on-prem/VPC deployment for enterprise. (source: cartesia.ai)
  • Failed requests do not consume credits; official Python and JavaScript SDKs and LiveKit/Pipecat integrations. (source: docs.cartesia.ai)

Conditions to check with Cartesia

  • Billing is a monthly subscription with a credit pool; Pro's effective rate is $50 per 1M characters and overage rates are $38 to $65 per 1M credits depending on plan. (source: cartesia.ai)
  • Free-plan concurrency is 2 TTS requests and Pro is 3; higher concurrency requires Startup or above. (source: docs.cartesia.ai)

Streaming and time to first audio

Cartesia: WebSocket streaming is listed and HTTP streaming is listed. Vendor-stated: first audio in under 90 ms (model latency), 'sub-90ms'. Not independently measured. Test from your own servers with your own text.

Voices and languages

Cartesia: languages listed: 44 languages for Sonic 3.6 (vendor-stated); custom voices: Instant voice cloning from a short clip (Pro and above); professional voice cloning on Startup and above; clones require verified consent.

Limits and formats

  • Concurrency: TTS concurrent requests by plan: Free 2, Pro 3, Startup 5, Scale 15, Enterprise custom. Exceeding returns 429. (source: docs.cartesia.ai)
  • Output formats listed: wav, mp3, raw: pcm_f32le, raw: pcm_s16le, raw: pcm_mulaw and raw: pcm_alaw.

API shape and switching cost

We could not tell whether Cartesia offers an OpenAI-compatible speech endpoint. Cartesia documents its own /tts/bytes, /tts/sse and /tts/websocket endpoints with a different request shape (model_id, transcript, voice, output_format); no OpenAI-style /v1/audio/speech route was found in the pages read.

What we could not confirm about Cartesia

  • Total number of voices in the voice library
  • Maximum characters per TTS request
  • SSML support is a Cartesia-specific tag subset (speed, volume, break/emotion), not full W3C SSML
  • Whether any OpenAI-compatible speech route exists
  • Credit use is 'approximately' 1 per character and may vary slightly with pre-processing
  • Plan prices and credit allotments are single-source (cartesia.ai/pricing); the docs pricing page confirms just the ~1 credit per character rate. Per-1M figures are derived by dividing plan price by credits

What to consider when choosing a Cartesia alternative

  • Price your monthly characters on each Cartesia tier you would use.
  • If you stream text in as a language model produces it, confirm that Cartesia's WebSocket input handles partial sentences the way your code expects.
  • Cartesia's per-request limit is not stated on the pages we reviewed, so test your longest text before you commit.
  • List the pronunciation problems you have today (names, acronyms, numbers) and test them, since not every service lets you correct them with markup.

Options besides Cartesia

Three other vendors from our dataset, chosen because they share Cartesia's category or pricing model, and ReadAloud, which we make. They are listed alphabetically, not ranked, and each summary comes from that vendor's own pages.

  • Deepgram Aura

    Deepgram Aura is also a text-to-speech API platform, and it lists a price per character as Cartesia does. Its pages mention HIPAA, SOC 2 and GDPR.

    Reviewed 2026-10-10 (source: deepgram.com)

  • Inworld TTS

    Inworld TTS is also a text-to-speech API platform, and it lists a price per character as Cartesia does. Inworld TTS lists an OpenAI-compatible speech endpoint. Its pages mention HIPAA, SOC 2 and GDPR.

    Reviewed 2026-10-10 (source: inworld.ai)

  • ReadAloud

    A streaming text-to-speech API: ReadAloud Live at $4 and ReadAloud Studio at $10 per 1M characters. English today.

    Disclosure: this is our product

  • Speechify API (SpeechifyAI Build)

    Speechify API (SpeechifyAI Build) is also a text-to-speech API platform, and it lists a price per character as Cartesia does. Its pages mention SOC 2.

    Reviewed 2026-10-10 (source: speechify.ai)

How ReadAloud differs from Cartesia

Cartesia's per-character figures are in the pricing list above, next to ReadAloud Live at $4 and ReadAloud Studio at $10. Live: one American English voice. Studio: several English voices. Requests are limited to 5,000 characters.

Details about Cartesia come from its public pages as they were on October 10, 2026. Cartesia may have changed them since, and a page that was unclear to us may be clear to you. Corrections: support@readaloudai.org. We make ReadAloud, so read this page with that in mind and check anything important with Cartesia directly.

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