Honest Retell AI Review 2025: Pros, Cons, Features & Pricing

Retell AI is built for businesses deploying LLM-powered voice agents in production environments. One of their clients has even replaced 8 team members with a single AI agent. It offers granular control over call flows, real-time streaming, barge-in handling, and the ability to integrate custom language models. With BYOC telephony and compliance support, it’s a strong fit for engineering-led teams managing high call volumes across global regions.

But with that flexibility comes tradeoffs. Retell is not designed for business users or teams seeking no-code deployment workflows. It lacks a full visual builder, real-time testing UI, and enterprise controls like RBAC and role-specific environments. For teams without dedicated engineering resources, this can slow down iteration and increase deployment complexity—especially when working with advanced fallback logic, prompt tuning, or voice cloning.

This review explores where Retell delivers at scale, and where it may require additional tooling or engineering lift to meet enterprise and cross-functional needs.

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Verdict: 6.7/10

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Key Features

• Voice streaming API: Connect real-time AI voice agents to phone or web using WebSocket-based audio streams.
• BYOC and telephony support: Integrate with Twilio, Telnyx, Vonage, or use Retell’s built-in carrier.
• ElevenLabs & PlayHT voices: Use premium speech synthesis with low-latency output.
• Interruption handling: Barge-in detection allows for human-like flow control.
• Multilingual support (30+ languages): Handle calls in multiple regions with manual language configuration.
• LLM prompt chaining: Compatible with GPT-4, Claude 3, or your own model.
• Post-call analysis: Includes basic transcripts, latency, and call summaries.
• Compliance-ready: SOC 2, HIPAA, and GDPR support for regulated industries.
• Calendar booking via Cal.com: AI agents can schedule appointments in real-time.

Retell AI Pricing

Retell AI uses modular, pay-as-you-go pricing with flexible tiers for startups and enterprise teams. All users begin with $10 in free credits, equal to about 60 minutes of calls.

• Voice Engine (ElevenLabs): $0.07/min
• Voice Engine (PlayHT/OpenAI): $0.08/min
• LLM (GPT-4o mini): $0.006/min
• LLM (GPT-4o): $0.05–$0.50/min (varies by tier)
• Telephony: $0.015/min (Retell stack)
• Knowledge Base usage: $0.005/min
• Batch Calls: $0.005/dial
• Branded Call ID: $0.10/outbound call
• Phone Number Rental: $2/month
• Extra KB (after 10 free): $8/month
• Concurrency Add-on: $8/line

Minimum spend for meaningful deployment starts at $3,000/month for enterprise teams. Discounts are offered at scale, with voice pricing dropping to $0.05/min or lower for high-volume customers.

There are no platform fees, subscriptions, or forced bundles. However, the total cost can rise depending on voice provider, LLM tier, and call volume.

Synthflow offers flat pricing at $0.08/min, bundling voice, LLM, logging, dashboards, and multi-language support. There are no setup costs or per-feature add-ons. Pricing is predictable and easier to manage at scale.

Synthflow requires a minimum annual budget of $15K, making it more accessible for agile teams that need fast deployment with full cost transparency. Named G2’s Best Estimated ROI winner for AI Agents this Spring, Synthflow delivers exceptional value with pricing that scales across businesses.

Verdict: 7.5/10
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Retell AI Usability and Interface

Retell AI is optimized for developers. It offers a minimal GUI for agent configuration but lacks a full visual flow builder. There’s no drag-and-drop interface, no real-time testing console, and no visual fallback mapping.

Prompt changes, context memory, and LLM chaining are handled through the API or SDK. Teams must simulate calls manually or create their own test infrastructure for quality assurance.

Non-technical stakeholders will need engineering support for setup, maintenance, and iteration.  In a recent IBM survey, the availability of more accessible AI tools was a top-three factor driving AI adoption​, underscoring that user-friendly design environments are crucial for teams adopting voice AI.

Synthflow features a true no-code interface with live agent testing, version control, and LLM debugging. It supports business and technical teams working together in the same workspace.

Verdict: 8/10
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Retell AI Voice Quality and Latency

Retell delivers ~800ms latency, which is adequate for most customer service and sales scenarios. It supports interruption handling, allowing agents to respond mid-sentence.

Voice quality depends on your selected provider. ElevenLabs offers emotional tone and realism, while PlayHT is less expressive. Retell does not currently support voice cloning, and speaker customization is limited.

The platform supports 30+ languages, but localization setup (prompt tuning, fallback routing) must be handled manually per use case.

Synthflow offers latency under 500ms, supports 50+ languages, and includes voice cloning and tone customization. All voice options are managed within the platform UI.

Verdict: 8/10
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Retell AI Developer Capabilities

Developer control is Retell’s strongest feature. Teams can use WebSockets for real-time streaming, route calls via custom webhooks, inject LLM prompts dynamically, and scale to thousands of concurrent sessions.

The platform supports warm transfers, DTMF/IVR navigation, CRM lookups, calendar scheduling, and batch outbound calls—all via API. There’s no limitation on LLM type or provider.

However, it lacks a built-in sandbox, version history, or prompt testing tools. Prompt flows must be built manually, and debugging complex fallback chains requires engineering time.

Synthflow offers a hybrid builder + API model. Developers can access full webhook support while non-engineers use the GUI. LLM chaining, fallback design, and sandbox testing are all built-in.

Verdict: 8.5/10
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Retell AI Security and Compliance

Retell meets compliance standards for regulated industries with certifications for SOC 2 Type II, HIPAA, and GDPR. Data is encrypted at rest and in transit, and deployments can scale globally with 99.99% uptime.

However, it lacks:

• ISO 27001
• Role-based access controls (RBAC)
• On-premise or VPC hosting
• Audit trails or access logs

These gaps may pose challenges for procurement or infosec reviews in healthcare, finance, and government sectors.

Synthflow includes SOC 2, HIPAA, ISO 27001, RBAC, audit logs, and optional on-prem hosting—making it a more complete solution for enterprise buyers.

Verdict: 8/10
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Retell AI Customer Support

Support is available via Discord and documentation. A demo agent repository is included for onboarding. There are no SLAs for standard users, and no live ticketing unless you're on the enterprise plan.

Retell updates frequently, but changelog access is inconsistent, and breaking changes have been reported during API updates.

Enterprise users gain access to a dedicated Slack channel and faster turnaround via assigned success teams.

Synthflow provides email, Slack, and account manager support from the start. Teams receive onboarding assistance, roadmap visibility, and issue escalation for mission-critical deployments.

Verdict: 7/10
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Retell AI App Review

Retell AI delivers powerful infrastructure for LLM-based phone agents—but it’s not a turnkey solution. It’s built for developers to comfortably orchestrate flows through code, APIs, and prompt logic.

It’s not ideal for business teams, rapid POCs, or non-technical workflows. Teams without internal engineers will need external help to reach production. Voice cloning, sandboxing, and visual tools are not included out of the box.

Verdict: 6.7/10

Synthflow: The Better Retell AI Alternative

If your team needs to launch agents fast with low latency, built-in compliance, and a visual builder—Synthflow is the better choice and better Retell AI Alternative. It combines real-time performance with enterprise support and no-code control.

Synthflow is purpose-built for teams that want to launch, scale, and iterate without code or infrastructure. It's faster to production, easier to manage, and better supported for enterprise needs.

FAQs

Is Retell AI free?
No. Retell offers $10 in free credits. After that, it charges per minute for voice, LLMs, telephony, and knowledge base usage. Phone numbers and advanced features are billed separately.

Is Retell AI HIPAA compliant?
Yes. Retell is SOC 2, HIPAA, and GDPR compliant. However, it lacks ISO 27001 and does not offer RBAC or audit trails.

Does Retell AI support multilingual conversations?
Yes. It supports 30+ languages depending on the voice provider, but configuration (prompts, fallbacks, agent behavior) must be done manually.

Can I use my own LLM with Retell?
Yes. Retell supports external LLMs. You can bring your own hosted models and only pay for voice and telephony.

Does Retell offer voice cloning?
No. Voice cloning is not currently supported natively, though ElevenLabs integration may offer a workaround with custom voices.

What is the minimum contract size for Retell AI?
Enterprise users should expect to budget at least $3,000/month for production usage, with pricing discounts kicking in at higher tiers.

How does Retell handle outbound calls?
Retell supports batch call campaigns, branded caller ID, and verified numbers to improve connection rates, making it the perfect AI call center solution for businesses.

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