Best for
Best for developers already on AWS who need speech synthesis inside an application, billed per character.
- Freelancers
- Small and mid-sized
- Enterprise
AI Voice & Speech Comparison
Amazon Polly vs. Synthflow
At a glance
At a glance
Best for
Best for contact centres and outsourcers that want phone agents built, branded and launched under one contract.
- Enterprise
Cataleo does not name a winner. Both statements come from the vendors themselves.
Full Comparison
| Criterion | Amazon Polly | Synthflow |
|---|---|---|
| Starting price | lower value Free tier, then from $4 per 1 million characters Pay-as-you-go by characters sent for synthesis, including spaces and most SSML tags. Standard $4, Neural $16, Generative $30 and Long-Form $100 per 1 million characters. Speech Marks requests are charged at the same rates. | From $30,000 / year Enterprise contracts start there and are scoped around call volume, concurrency, telephony setup, integrations, security needs and launch support. No self-serve tier is published. |
| Free trial | AWS Free Tier: 5 million Standard characters a month, plus 1 million Neural, 500,000 Long-Form and 100,000 Generative characters a month for the first 12 months | Not stated |
| Commercial use | Not stated | Yes, under an enterprise contract |
| Output | Synthesised speech as MP3, Ogg Vorbis or raw PCM, plus Speech Marks metadata | Voice and chat agents for inbound and outbound phone calls, including white-labelled agents resold under a partner's brand |
| API | Yes, the Amazon Polly API through the AWS SDKs and the AWS CLI | Yes, a public Platform API, plus an MCP server for MCP-capable clients |
| Languages | Voices in 42 languages and language variants | Over 30, plus a multilingual mode that switches languages within one call |
| Hosting | Cloud (AWS) | Cloud, with region-based hosting |
| Voice cloning | Brand Voice only, and not as a self-service feature. It is a custom engagement in which the Amazon Polly team builds a Neural voice for the exclusive use of one organisation, covering persona, casting an actor, recording their speech and training the model, after which the voice is released to that customer's AWS account. It starts with an AWS account manager rather than an upload | Cloning happens in ElevenLabs, not in Synthflow. The voice selector offers Synthflow's own TTS with twelve built-in voices and the ElevenLabs models from Turbo v2 and Flash v2.5 up to v3; a cloned or provider-specific voice is added through Imported > Import Voice by pasting the provider voice ID, or by connecting your own ElevenLabs API key so that account's custom voices appear in the selector. The vendor warns that a synthesiser model your own ElevenLabs plan lacks can mean lower quality or higher latency on your key |
| Real-time use | Yes, the API returns an audio stream that an application can begin playing as it arrives, in near real time, with a choice of sampling rates to trade bandwidth against audio quality | Yes, live inbound and outbound calls, with IVR handling for outbound agents, voicemail and silence handling, in-call SMS and WhatsApp messaging, and WhatsApp Business calling. The vendor states 99.99% uptime on its own telephony infrastructure |
| Speech-to-speech and dubbing | No. Polly synthesises speech from text and nothing else. Transcription and translation are separate AWS services rather than features of this one | Not documented. The voice documentation covers text-to-speech for live agents, with a speaker and a synthesis model chosen per agent, and carries no speech-to-speech conversion and no dubbing |
| Editing and controls | SSML for phrasing, emphasis, intonation, pitch, rate and volume, custom Amazon SSML tags such as the Newscaster speaking style, custom lexicons that set the pronunciation of particular words through IPA-style phonemes, and Speech Marks metadata for speech-synchronised facial animation or word highlighting | Flow Designer, a node-based canvas with conversation, message, branch, jump and custom action nodes, or a simpler prompt builder, plus a multi-agent system for several flows behind one agent, voice model and pacing settings, manual testing, automated simulations and custom evaluations that score calls against business goals |
| Consent and trust | Brand Voice is a managed engagement rather than an upload, so a custom voice exists only where an actor has been cast and recorded for that purpose, and the finished voice is restricted to the commissioning organisation's AWS account IDs. There is no self-service cloning path that could be pointed at a voice without its owner taking part | SOC 2, HIPAA, PCI DSS, GDPR and ISO 27001, with encryption, audit logs and region-based hosting. Per-agent controls decide whether recordings and transcripts are kept at all, cap retention at 30 days, and redact personal data from transcripts, webhook payloads and logs |
| MCP-ready | No | stated Yes |
| Deployment | Cloud (SaaS), Browser-based | Cloud (SaaS), Browser-based |
| Support | Not stated | Email helpdesk |
| Onboarding | Documentation and knowledge base | more entries Documentation and knowledge base, Personal consulting |
| Company size | more entries Freelancers, Small and mid-sized, Enterprise | Enterprise |
| Integrations | Not stated | HubSpot, Salesforce, Zapier, Cal.com, GoHighLevel, Twilio, Genesys, Avaya, Five9, Cisco, RingCentral |
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The short version
Key Differences
- Starting price Amazon Polly Free tier, then from $4 per 1 million characters Synthflow From $30,000 / year
- Company size Amazon Polly Freelancers, Small and mid-sized, Enterprise Synthflow Enterprise
- Hosting Amazon Polly Cloud (AWS) Synthflow Cloud, with region-based hosting
- Languages Amazon Polly Voices in 42 languages and language variants Synthflow Over 30, plus a multilingual mode that switches languages within one call
- MCP-ready Amazon Polly No Synthflow Yes
Every line is one datapoint from the table above, picked automatically. Nothing here is written text.
The trade-offs
Strengths and Limitations
Amazon Polly
Strengths
- Four voice engines let quality be traded against cost per character, from $4 to $100 per million
- Generous free tier, with 5 million Standard characters a month that does not expire
- Generated speech may be cached and replayed at no additional cost
- Speech Marks and custom lexicons cover lip-sync and awkward pronunciations properly
- Brand Voice cannot be used without the voice owner being cast and recorded
Limitations
- Text to speech only: no transcription, translation or dubbing in this service
- No self-service voice cloning, and Brand Voice starts with an AWS account manager
- The Generative and Long-Form engines cover far fewer voices than Standard and Neural
- Long-Form voices cost $100 per million characters, twenty-five times the Standard rate
- Useful only from code, so it suits developers rather than anyone wanting an editor
Synthflow
Strengths
- No-code Flow Designer with a multi-agent system, so a non-developer can build and change call flows
- Connects to existing telephony and contact centre stacks over SIP, including Genesys, Avaya, Five9, Cisco and RingCentral
- White-labelled deployments for partners reselling voice agents under their own brand
- SOC 2, HIPAA, PCI DSS, GDPR and ISO 27001, with agent-level retention and PII redaction controls
Limitations
- No self-serve or trial tier is published; the only listed plan is an enterprise contract from $30,000 per year
- Pricing is scoped by sales, so the cost of a given call volume is not knowable from the website
- Latency figures differ between the vendor's own pages, so the published number is not a specification to rely on
- A cloned voice has to be created in a separate ElevenLabs account and imported, so it means a second subscription alongside Synthflow
Plans
Pricing
Amazon Polly
- AWS Free Tier Free 5 million Standard characters a month. Neural 1 million, Long-Form 500,000 and Generative 100,000 characters a month for the first 12 months.
- Standard voices $4 Per 1 million characters for speech or Speech Marks requests, outside the free tier.
- Neural voices $16 Per 1 million characters for speech or Speech Marks requests, outside the free tier.
- Generative voices $30 Per 1 million characters for speech requests, outside the free tier.
- Long-Form voices $100 Per 1 million characters for speech or Speech Marks requests, outside the free tier.
Synthflow
- Enterprise $30,000 Per year, the stated starting point. Scoped around call volume, concurrency, telephony setup, integrations and security needs, and covers implementation, onboarding, testing, training, launch support and ongoing optimisation, with SLA and support terms set in the contract.
What users say
Review Scores · opens after launch
Amazon Polly
- Ease of use
- Not rated yet
- User interface
- Not rated yet
- Onboarding
- Not rated yet
- Support and service
- Not rated yet
- Value for money
- Not rated yet
- Features
- Not rated yet
No reviews yet. Be the first to review this tool. Every review is checked for fairness before it appears, and the vendor cannot have one removed.
Synthflow
- Ease of use
- Not rated yet
- User interface
- Not rated yet
- Onboarding
- Not rated yet
- Support and service
- Not rated yet
- Value for money
- Not rated yet
- Features
- Not rated yet
No reviews yet. Be the first to review this tool. Every review is checked for fairness before it appears, and the vendor cannot have one removed.
Where this comes from
Where this comes from
Amazon Polly https://aws.amazon.com/polly/ · checked against the official source on 2026-09-13
Synthflow https://synthflow.ai · checked against the official source on 2026-09-13
This table lists factual criteria taken from information the vendors publish themselves. For how we put it together, see the methodology.