OfflineTTS vs Amazon Polly: Free Local TTS vs AWS Cloud

Amazon Polly is AWS’s cloud-based text-to-speech service, popular for its low per-character pricing and tight integration with AWS services. OfflineTTS takes the opposite approach: zero-cost, browser-based, and fully local.

Here’s how they stack up.

Quick Comparison

Feature	OfflineTTS	Amazon Polly
Price	Free	$4/1M chars (Standard + Neural)
Free Tier	Unlimited (all features)	1M chars/mo (first 12 months)
Voice Count	54 + Supertonic/Piper/Kitten	100+
Languages	9	30+
Voice Quality	A/A- (Kokoro 82M)	Neural (good), Generative (best)
Offline	✅ After initial model download	❌ Requires internet
Privacy	✅ Text never leaves your device	❌ Text sent to AWS servers
SSML	❌ (plain text)	✅ Full SSML
API	❌ (browser only)	✅ REST API, AWS SDKs
Signup	❌ None	✅ AWS account required
Voice Cloning	❌	❌
Export	WAV, MP3	MP3, OGG, PCM

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Pricing: Truly Free vs $4/1M

OfflineTTS generates unlimited speech at zero cost — no free tier expiration, no character limits, no credit card required. It runs on your device after the one-time model download.

Amazon Polly charges $4 per 1 million characters for both Standard and Neural voices — much simpler than Google Cloud or Azure’s multi-tier pricing. The free tier gives you 1 million characters per month for the first 12 months.

Volume	OfflineTTS	Amazon Polly
100K chars/month	$0	$0 (free tier)
1M chars/month	$0	$0 (free tier)
5M chars/month	$0	$20
10M chars/month	$0	$40
100M chars/month	$0 (or self-host)	$400

At scale, OfflineTTS stays at zero. Amazon Polly at $4/1M is the cheapest cloud TTS API — Google charges $4–16, Azure $4–16, ElevenLabs $165+. For high-volume production, Polly is the most cost-effective cloud option.

Winner: OfflineTTS for cost. Amazon Polly for cheapest cloud API pricing.

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Voice Quality

Amazon Polly offers three voice tiers:

• Standard — concatenative synthesis, noticeably robotic
• Neural — improved naturalness, the most commonly used tier
• Generative — newest, highest quality (launched 2024)

OfflineTTS uses Kokoro 82M (A-grade), Piper, and Supertonic. Kokoro’s top voices match or exceed Polly’s Neural tier in naturalness for short-to-medium speech.

Where Polly excels:

• Consistency — decades of tuning, very reliable output
• SSML control — full SSML for precise prosody
• Generative voices — new gen-AI voices are competitive with Kokoro

Where OfflineTTS excels:

• No latency — instant generation on WebGPU
• Cost at volume — free vs $4/1M adds up
• Privacy — no data transmitted

Winner: Tie for quality. Polly has more options; OfflineTTS’s best voices compete well.

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Privacy & Offline

OfflineTTS processes everything on your device. Text never reaches a server. English works fully offline after the model download. Non-English uses a lightweight phonemization service before local synthesis.

Amazon Polly sends your text to AWS servers. While AWS has strong security certifications, the architecture requires data transmission for every request. No offline mode exists.

For applications handling sensitive data — legal, medical, financial — OfflineTTS’s local-only processing eliminates the compliance risk of transmitting speech data.

Winner: OfflineTTS — on-device processing is fundamentally more private.

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SSML & Speech Marks

Amazon Polly supports:

• Full SSML: <break>, <prosody>, <emphasis>, <say-as>, <phoneme>, <sub>, <lang>, <audio>, <p>/<s>
• Speech Marks — word-level timing data (word boundaries, sentence boundaries, visemes)
• Lexicons — custom pronunciation dictionaries

OfflineTTS accepts plain text only. No SSML. No speech marks. Pacing is controlled through punctuation.

Winner: Amazon Polly — SSML and speech marks are essential for production workflows.

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API & Integration

Amazon Polly provides:

• REST API and AWS SDKs (Python, Node.js, Java, .NET, Go, etc.)
• SynthesizeSpeech and StartSpeechSynthesisTask (async batch)
• Integration with AWS services (Lambda, S3, CloudFront)
• Lexicon management for custom pronunciations

OfflineTTS is browser-only with no API. For programmatic TTS, use the Kokoro Python package directly.

Winner: Amazon Polly for API integration. Kokoro Python for local scripting.

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Use Cases

YouTube and Content Creation

OfflineTTS wins on cost. Unlimited free generation means you can iterate endlessly. Polly is more cost-effective than other cloud APIs if you need SSML.

Audiobooks

Amazon Polly’s SSML and Speech Marks are useful for audiobook production. At $4/1M chars, a 100K-word novel costs about $2.40 — very affordable. OfflineTTS is free but has no SSML.

E-Learning

Polly’s SSML gives fine-grained control over instructional narration. OfflineTTS’s privacy matters for courses with sensitive content.

Enterprise Applications

Amazon Polly’s AWS integration and reliability make it the standard choice for enterprise TTS in the AWS ecosystem. OfflineTTS doesn’t support programmatic integration.

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The Bottom Line

Choose OfflineTTS if you:

• Want truly unlimited free TTS
• Need privacy — text stays on your device
• Need offline capability
• Don’t need SSML or API access
• Produce short-to-medium form content

Choose Amazon Polly if you:

• Need the cheapest cloud-based TTS API ($4/1M)
• Require SSML for precise prosody control
• Need Speech Marks for word-level timing
• Are building an application in the AWS ecosystem
• Need custom pronunciation lexicons

Winner for most users: OfflineTTS for personal use. Amazon Polly for AWS-native production.

Try OfflineTTS — free, private, runs in your browser →