Synthflow vs Retell AI Comparison 2025
Kickstart smarter, hands‑free interactions with Synthflow and Retell AI—two powerful voice‑assistant platforms built for modern businesses. Below, you’ll find a clear, side‑by‑side look at their core features, from easy no‑code setup to advanced developer controls. Browse the comparison to see which AI assistant fits your workflow and helps you deliver standout voice experiences.
1. Core Functional Capabilities
Task Automation & Conversational Scope
🔹Synthflow supports end‑to‑end call workflows—routing, voicemail, SMS follow‑ups—and offers a drag‑and‑drop builder for multi‑turn dialogues.
🔸Retell AI provides low‑code agent building, batch calling, warm transfers, and built‑in simulation testing for complex multi‑step flows.
Better: Retell AI for deep workflow validation and customization. Synthflow for rapid no‑code launches.
Voice Recognition Accuracy
🔹Synthflow uses advanced LLMs and phone‑grade transcription optimized for accents and noise, plus spam filtering.
🔸Retell AI delivers sub‑second STT in 19+ languages, with post‑call analytics to identify and correct mis‑recognitions.
Better: Retell AI for broader language support and built‑in accuracy analytics.
Natural Language Understanding & Context Handling
🔹Synthflow employs GPT‑4‑level NLU with context persistence across nodes, handling basic follow‑ups and escalation triggers.
🔸Retell AI allows custom LLM selection, fine‑tuned context windows, and interruption handling for richer intent interpretation.
Better: Retell AI for more robust NLU and dynamic context management.
Real‑Time Processing & Latency
🔹Synthflow achieves sub‑500 ms round‑trip latency via optimized cloud and edge routing.
🔸Retell AI guarantees < 500 ms latency, no concurrency limits, and a 99.99 % SLA for consistent performance.
Better: Retell AI thanks to its explicit SLA and unconstrained concurrency.
Audio Quality & Voice Naturalness
🔹Synthflow integrates expressive voices with natural prosody and custom brand‑voice cloning.
🔸Retell AI offers built‑in voices optimized for clarity, empathy, dynamic modulation, and branded caller ID.
Better: Synthflow for wider voice selection. Retell AI for enterprise‑grade modulation and branding.
Voice Customization & Emotional Tone
🔹Synthflow’s no‑code editor adjusts pitch, rate, and style, with prompt templates for personality embedding.
🔸Retell AI provides low‑code prosody overrides, custom LLMs, and scripted persona traits for brand consistency.
Better: Retell AI for finer developer‑level control over emotional tone.
2. Integration & Compatibility
Device & Platform Support
🔹Synthflow runs on web, Twilio‑powered mobile/in‑car systems, and private‑cloud on‑premises.
🔸Retell AI supports web, SIP trunking (any VoIP), SMS channels, and embeds via an API‑first design.
Better: Retell AI for broader device reach and seamless SIP integration.
Smart Home & IoT Ecosystem Integration
🔹Synthflow offers basic IoT triggers via Zapier; native Matter/Zigbee support is lacking.
🔸Retell AI provides webhook‑based IoT hooks, native integrations with major automation platforms, with Matter support upcoming.
Better: Retell AI for richer third‑party IoT connectivity today.
API & Third‑Party Service Integration
🔹Synthflow includes REST APIs, Zapier, CRM connectors, and Node.js/Python SDKs.
🔸Retell AI delivers a full Voice AI API, low‑code SDKs, pre‑built plugins, and auto‑sync knowledge‑base features.
Better: Retell AI for more extensive out‑of‑the‑box integrations.
Business & Productivity Tool Integration
🔹Synthflow connects to major CRMs, calendars, and SMS channels, updating records in real time.
🔸Retell AI integrates natively with CRM, scheduling tools, and BI platforms, with webhook support for any system.
Better: Retell AI thanks to modular connectors and BI‑friendly outputs.
3. User Experience & Personalization
User Interface & Ease of Use
🔹Synthflow offers an intuitive no‑code drag‑and‑drop builder with guided onboarding and dashboard metrics.
🔸Retell AI features a low‑code agent builder, live simulation testing, and step‑by‑step wizards with in‑dashboard analytics.
Better: Synthflow for pure no‑code simplicity. Retell AI for a balanced low‑code experience.
Customization & Personalization
🔹Synthflow learns basic preferences via session memory and time/location context, with manual flow edits for deeper personalization.
🔸Retell AI persistently stores profiles, adapts dialogue from past interactions, and exposes personalization APIs with sentiment analysis.
Better: Retell AI for automated, API‑driven personalization.
Language & Accent Support
🔹Synthflow supports six core languages/accents with real‑time translation; additional languages require custom prompts.
🔸Retell AI natively supports 19+ languages and dozens of dialects, with region‑aware terminology synchronization.
Better: Retell AI for superior global coverage.
Offline & On‑Device Capability
🔹Synthflow offers on‑device TTS in private cloud but relies on cloud ASR; local containers remain in beta.
🔸Retell AI requires cloud for ASR/TTS today, with offline mode planned; no on‑device SDK yet.
4. Security, Privacy & Compliance
Privacy & Data Security
🔹Synthflow provides end‑to‑end encryption, HIPAA compliance, and configurable consent and retention controls.
🔸Retell AI holds SOC 2 Type 1&2, HIPAA, and GDPR compliance, with audit logs and role‑based access control.
Better: Retell AI for more transparent compliance features and audit capabilities.
Regulatory & Compliance Certifications
🔹Synthflow cites HIPAA and encryption standards but lacks public SOC 2/GDPR details.
🔸Retell AI clearly lists SOC 2 Type 1&2, HIPAA, and GDPR certifications.
Better: Retell AI for broader documented certifications.
5. Performance, Reliability & Cost
Reliability & Uptime Guarantees
🔹Synthflow omits published SLAs or uptime metrics, leaving mission‑critical reliability unclear.
🔸Retell AI guarantees 99.99 % uptime with automatic failover and unconstrained concurrency.
Better: Retell AI due to explicit SLA and robust failover design.
6. Free and Paid Packages
Free & Paid Pricing Models
🔹Synthflow offers a 14‑day trial, then tiered plans at set per‑minute rates plus overages, bundling features per tier.
🔸Retell AI uses pay‑as‑you‑go per‑minute pricing with no platform fees, modular add‑ons, and volume discounts.
Synthflow
- Free Trial:
- Available (no credit card required)
- Includes limited minutes (around 50 minutes) and 10 concurrent calls
- Unlimited assistants
- Basic workflow builder access
- Starter Plan ($29/month):
- 50 minutes included
- 10 concurrent calls
- Unlimited assistants
- Access to workflow builder and basic integrations
- Pro Plan ($450/month):
- 2,000 minutes included
- 25 concurrent calls
- Batch campaigns support
- Real-time booking and call transfer features
- Growth Plan ($900/month):
- 4,000 minutes included
- 50 concurrent calls
- 25 subaccounts
- White-glove onboarding and dedicated success manager
- Agency Plan ($1,400/month):
- 6,000 minutes included
- 100 concurrent calls
- 10,000 subaccounts
- White-label platform
- Enterprise-grade support and uptime SLA
- Enterprise:
- Custom pricing based on volume and needs
- Unlimited concurrent calls and workflows
- Full customization and integration support
Retell
- No detailed official pricing or free tier information publicly available as of May 2025.
- Typically, Retell offers voice AI solutions focused on storytelling, voice cloning, and audio content creation.
- Pricing is usually customized based on usage, features, and enterprise needs.
- May provide free trials or demos on request.
- Paid plans likely include increased usage limits, premium voices, API access, and priority support.
🔹 Synthflow – Read More »
🔸 Retell AI – Read More »
7. Support & Ecosystem
Customer Support & Documentation
🔹Synthflow provides a Help Center, API docs, and an onboarding academy; community forums are limited.
🔸Retell AI offers extensive docs, live chat, a community Discord, and a certified partner network.
Better: Retell AI for a richer support ecosystem and implementation partners.
Developer Community & Third‑Party Extensions
🔹Synthflow’s integrations include Zapier and ElevenLabs; no open‑source SDKs yet.
🔸Retell AI features an app marketplace, open‑source examples, and community‑contributed templates.
Better: Retell AI for a more active developer community and extension ecosystem.
Comparison Summary
| Criterion | Synthflow Rating | Retell AI Rating | Better & Why |
| Task Automation & Conversational Scope | ★★★★☆ | ★★★★★ | 🔸Retell AI’s low‑code builder and built‑in simulation testing handle complex, multi‑step workflows more robustly than Synthflow’s template‑based flows. |
| Voice Recognition Accuracy | ★★★★☆ | ★★★★★ | 🔸Retell AI’s sub‑second STT across 30+ languages with analytics for tuning outperforms Synthflow’s core language set and basic noise filtering. |
| NLU & Context Handling | ★★★★☆ | ★★★★★ | 🔸Retell AI’s custom LLM selection and interruption handling deliver richer intent management than Synthflow’s built‑in GPT‑4‑level NLU. |
| Real‑Time Processing & Latency | ★★★★★ | ★★★☆☆ | 🔹Synthflow consistently achieves < 500 ms round‑trip latency, beating Retell AI’s typical 700–1500 ms range Synthflow. |
| Audio Quality & Voice Naturalness | ★★★★★ | ★★★★☆ | 🔹Synthflow’s ElevenLabs‑powered voices offer more expressive prosody than Retell AI’s standard models. |
| Voice Customization & Emotional Tone | ★★★★☆ | ★★★★★ | 🔸Retell AI’s low‑code prosody overrides and custom LLMs enable finer emotional tuning than Synthflow’s slider‑based adjustments. |
| Device & Platform Support | ★★★★☆ | ★★★★★ | 🔸Retell AI’s SIP trunking, SMS channels, and API‑first design span more platforms than Synthflow’s Twilio‑centric model. |
| Smart Home & IoT Integration | ★★★☆☆ | ★★★★☆ | 🔸Retell AI’s native webhooks for major automation tools deliver richer IoT hooks compared to Synthflow’s Zapier‑only triggers. |
| API & Third‑Party Integration | ★★★★☆ | ★★★★★ | 🔸Retell AI’s modular SDKs and pre‑built plugins exceed Synthflow’s REST‑and‑Zapier approach. |
| Business & Productivity Integration | ★★★★☆ | ★★★★★ | 🔸Retell AI’s native CRM/BI connectors surpass Synthflow’s standard HubSpot and calendar integrations Synthflow. |
| UI & Ease of Use | ★★★★★ | ★★★★☆ | 🔹Synthflow’s drag‑and‑drop, no‑code builder is more approachable for non‑technical users than Retell AI’s low‑code console Synthflow AI. |
| Customization & Personalization | ★★★☆☆ | ★★★★★ | 🔸Retell AI’s persistent user profiles and sentiment APIs automate personalization beyond Synthflow’s manual flow edits. |
| Language & Accent Support | ★★★★☆ | ★★★★★ | 🔸Retell AI natively covers 30+ languages/dialects vs. Synthflow’s six core locales Synthflow. |
| Offline & On‑Device Capability | ★★★☆☆ | ★★★☆☆ | Both rely on cloud ASR/TTS with limited on‑device support today, tying them evenly. |
| Privacy & Data Security | ★★★★☆ | ★★★★★ | 🔸Retell AI’s SOC 2 audits and role‑based controls build on Synthflow’s encryption and HIPAA offerings for stronger compliance. |
| Compliance Certifications | ★★★☆☆ | ★★★★★ | 🔸Retell AI publicly lists SOC 2, HIPAA, and GDPR certifications; Synthflow only cites HIPAA generally. |
| Reliability & Uptime | ★★★☆☆ | ★★★★★ | 🔸Retell AI’s 99.99 % SLA with automatic failover outshines Synthflow’s unpublished uptime metrics. |
| Pricing Models | ★★★★☆ | ★★★★★ | 🔸Retell AI’s $0.07/min pay‑as‑you‑go scales more transparently and cost‑effectively than Synthflow’s tiered bundles. |
| Support & Documentation | ★★★★☆ | ★★★★★ | 🔸Retell AI’s live chat, Discord community, and partner network surpass Synthflow’s limited forums. |
| Developer Ecosystem | ★★★☆☆ | ★★★★★ | 🔸Retell AI’s app marketplace and open‑source templates foster a more vibrant community than Synthflow’s nascent library. |
AI Voice Assistant Tools – See What Fits You Best
Explore and compare the top AI voice tools to find your best match for any task.
What Is Synthflow AI Assistant?
Synthflow is a no‑code voice‑AI platform that lets business users build and deploy phone based and web chat agents via drag‑and‑drop workflows. It integrates prebuilt templates for tasks like appointment booking, SMS follow‑up, and call routing—so nontechnical teams can launch conversational agents in minutes without writing code.
What Is Retell AI Assistant?
Retell AI is a low code voice AI solution aimed at developers and enterprises. It provides SDKs and APIs to script complex dialogue flows, choose custom language models, and run simulation tests. Retell AI emphasizes fine‑grained control over prosody, multi‑language support, and enterprise SLAs for high‑volume, mission‑critical deployments.
Frequently Asked Questions: Synthflow vs. Retell AI
1. What deployment options do Synthflow and Retell AI offer for building AI voice assistants?
🔹 Synthflow provides a true no‑code, drag‑and‑drop platform that lets non‑technical teams spin up voice agents and call workflows in minutes without writing a line of code.
🔸 Retell AI uses a low‑code approach with SDKs and APIs so developers can deeply customize conversational logic, integrate custom language models, and run simulation tests before going live.
2. How do they compare in voice recognition accuracy across accents and languages?
🔹 Synthflow supports real‑time, phone‑grade transcription optimized for six core languages and common accents, with built‑in noise filtering and spam detection.
🔸 Retell AI extends that to dozens of languages and dialects, offering sub‑second speech‑to‑text and post‑call analytics to continually tune accuracy for global users.
3. Which platform delivers lower latency for real‑time conversations?
🔹 Synthflow consistently achieves under 500 ms round‑trip latency using optimized edge routing, ensuring seamless, human‑like exchanges.
🔸 Retell AI typically measures 700–1,500 ms latency but backs performance with a 99.99 % uptime guarantee and unconstrained concurrency for enterprise scale.
4. Can I customize voice personality and emotional tone on each platform?
🔹 Synthflow’s no‑code editor offers sliders for pitch, rate, and style plus template‑based prompt embeds to craft friendly or formal personas without code changes.
🔸 Retell AI lets developers override prosody parameters via low‑code scripts and select custom language models to fine‑tune empathy, humor, or brand voice at a granular level.
5. What integrations exist for CRMs, calendars, and IoT devices?
🔹 Synthflow connects out‑of‑the‑box to major CRMs, calendars, and triggers IoT actions via Zapier webhooks for simple automation flows.
🔸 Retell AI offers native connectors for scheduling tools, SIP trunking for any VoIP, webhook hooks for leading automation platforms, plus BI‑friendly exports for analytics pipelines.
6. How do their pricing models differ for startups and enterprises?
🔹 Synthflow provides a 14‑day free trial then tiered monthly bundles at fixed per‑minute rates, bundling features into set packages for predictable billing.
🔸 Retell AI uses transparent pay‑as‑you‑go pricing with no platform fees, plus volume discounts and modular add‑ons (e.g., branded caller ID) for flexible scaling.
7. Which platform ensures stronger security and regulatory compliance?
🔹 Synthflow delivers end‑to‑end encryption, HIPAA‑level safeguards, and customizable data‑retention controls to protect sensitive conversations.
🔸 Retell AI not only meets HIPAA requirements but also provides SOC 2 and GDPR compliance, with audit logs and role‑based access controls for full enterprise transparency.