Retell AI vs Synthflow (2026): No Code Voice Agents Compared
Two no code voice agent platforms, one self serve and one enterprise only, compared on published pricing, builders, telephony, integrations, compliance and reviews, as of October 2026.
By , research by the BestBots team · Updated Oct 19, 2026
Fact checked against each company's published pricing, documentation and verified user ratings. How we score
Pick Retell AI if you want a no code voice agent you can start today: a drag and drop builder plus API, $0.055 a minute infra with every component priced publicly (about $0.0946 all in on a budget stack), 20 free concurrent calls and HIPAA included. Pick Synthflow if you are an enterprise contact center that wants its own telephony, Genesys or Avaya connectors and vendor engineers on a $30,000 plus contract.
Side by side
| Spec | Retell AI | Synthflow |
|---|---|---|
| BestBots Score | 4.6 | 3.9 |
| Starting price | $0.055 per minute | Quote only |
| Pricing model | per minute, pay as you go | annual enterprise contract |
| Free trial | $10 in free credits | None listed |
| Per minute cost | $0.055 voice infra plus LLM ($0.0016 to $0.32), voice ($0.015 to $0.10) and telephony ($0.015 US Twilio or Telnyx) | Not published; contracts from $30,000 per year |
| Latency | About 600 ms, per Retell's homepage | Synthflow claims sub 100 ms |
| Telephony | Retell numbers via Twilio, Vonage, or your own SIP trunk at no Retell charge | Synthflow native telephony, SIP trunking, Cisco, Avaya, Genesys, RingCentral |
| Concurrency | 20 concurrent calls free, then $8 per line per month | Custom, planned per contract |
| Languages | Multilingual agents supported; the dashboard lists current languages | Multilingual; count not published |
| HIPAA | Yes, listed as HIPAA ready | Yes |
| SOC 2 | SOC 2 Type II | SOC 2, plus PCI DSS, GDPR and ISO 27001 |
The short answer
- Choose Retell for small and mid size businesses, agencies, and enterprises that want to self serve and see the price before signing.
- Choose Synthflow for BPOs and large contact centers on Cisco, Avaya, Genesys or RingCentral that want implementation done for them.
Pricing
| Item | Retell AI | Synthflow |
|---|---|---|
| Model | Pay as you go, no monthly fee | Annual enterprise contract |
| Published rate | $0.055 a minute infra plus LLM, voice, telephony | None |
| Minimum | None | From $30,000 a year |
| Budget all in | About $0.0946 a minute | Not published |
| Recommended stack | About $0.149 a minute | Not published |
| Free start | $10 credits | Demo |
| Concurrency | 20 free, $8 per extra line | Planned per contract |
| HIPAA | Included, custom BAA on Enterprise | Included in enterprise scope |
| Implementation | Self serve, dedicated support on Enterprise | Forward deployed engineers |
Break even
$30,000 a year is $2,500 a month. On Retell that buys about 26,400 minutes a month on the budget stack, or about 16,800 on the recommended stack with GPT 5.6 Terra. If your volume is lower, Synthflow's floor costs more. At higher volume, ask Synthflow for an effective rate per minute and compare. All tracked prices are on the AI Price Index.
Models and features
| Feature | Retell AI | Synthflow |
|---|---|---|
| Builder | Drag and drop flow builder, plus API | Visual Flow Designer with subflows |
| Models | Choose from GPT, Claude and Gemini models at listed per minute rates; speech to speech GPT Realtime | Managed by Synthflow |
| Voices | Retell, Minimax, Fish, Cartesia, OpenAI, Inworld, ElevenLabs | Not itemized |
| Testing | Testing and QA tools; AI QA add on | Test Center with simulated calls, AI sandbox with rollback |
| Monitoring | Call analytics, AI QA | Real time monitoring, Auto QA |
| Telephony | Twilio or Telnyx numbers, free SIP and custom telephony | Own network, SIP and PBX, Cisco, Avaya, Genesys, RingCentral |
| Channels | Voice, chat agents, SMS | Voice, chat, SMS, WhatsApp |
| Integrations | HubSpot, Cal.com, Make, n8n, GoHighLevel and others | 200+, including Salesforce, HubSpot, GoHighLevel, Zapier, Cal.com |
| Latency claim | About 600 ms | Under 100 ms (method not stated) |
| Scale | 20 free lines, no cap on Enterprise | Synthflow cites 65M+ calls a month |
Head to head scenarios
Dental office or home services company
Winner: Retell. Start with $10 in credits, build a booking agent in the visual builder, connect Cal.com and pay per minute. Synthflow's minimum is larger than most small businesses' annual phone budget.
Agency building agents for many clients
Winner: Retell. Pay as you go per client, a full public price sheet to quote from, and integrations with GoHighLevel, Make and n8n. Synthflow's enterprise contract model does not fit many small accounts.
BPO on Genesys automating tier 1 calls
Winner: Synthflow. Native contact center connectors, its own telephony, a Test Center and engineers who launch in weeks are built for this.
Healthcare network with 15,000 minutes a month
Winner: Retell. About $2,235 a month on the recommended stack with HIPAA included, under Synthflow's $2,500 floor and without an annual commitment.
Team that wants the vendor to own delivery
Winner: Synthflow. Implementation, onboarding, testing, training and launch support are in the contract. Retell offers dedicated implementation support on Enterprise, but self serve is the default.
Privacy
Retell lists SOC 2 Type II, HIPAA, GDPR and ISO 27001, with PII redaction, safety guardrails, opt out of recording and transcription, and custom data retention, SSO and BAA on Enterprise.
Synthflow lists SOC 2, HIPAA, PCI DSS, GDPR and ISO 27001, with encryption, audit logs, EU and US hosting, and MSA, DPA and security reviews in its contracts. Running its own telephony keeps call routing with one vendor.
Reviews
Retell holds 4.9 on Trustpilot from 810 reviews; some reviewers mention pauses of 1.5 to 2.5 seconds and slow support replies. Synthflow holds 4.1 from 215, with only 6 reviews in the last year and recent complaints about slow support and billing after cancellation.
Verdict
Retell wins for most buyers: public pricing, a no code builder plus API, 20 free lines, included HIPAA and a much stronger review record, with no contract. Synthflow wins for enterprise contact centers that want contact center connectors, in house telephony and a vendor that delivers the project, and that can commit at least $30,000 a year. Read the Retell AI review and the Synthflow review, or see Vapi vs Synthflow.
Frequently asked questions
Is Retell AI or Synthflow better?
Retell AI is better for most businesses: every price is public, you can start with $10 in credits, 20 concurrent calls and HIPAA are included, and it holds 4.9 on Trustpilot from 810 reviews. Synthflow is better for enterprise contact centers that want its own telephony, Genesys and Avaya connectors and vendor engineers, and can commit $30,000 a year.
Is Retell cheaper than Synthflow?
For any volume below roughly 26,000 minutes a month on a budget stack, yes, because Synthflow's floor is $30,000 a year, $2,500 a month. Above that, compare Synthflow's quoted effective rate per minute with Retell's $0.0946 to $0.159.
Do both have no code builders?
Yes. Retell has a drag and drop flow builder plus an API. Synthflow has a visual Flow Designer with subflows that act as specialized agents, plus a Test Center and AI sandbox.
Which has better telephony?
Synthflow runs its own telephony network and connects to SIP, PBX, Cisco, Avaya, Genesys and RingCentral. Retell offers numbers on Twilio or Telnyx at $0.015 a minute in the US and charges nothing for SIP trunking or custom telephony.
Which is better for HIPAA?
Both list HIPAA. Retell lists SOC 2 Type II and HIPAA with no published surcharge, and custom BAAs on Enterprise. Synthflow lists SOC 2, HIPAA, PCI DSS, GDPR and ISO 27001 in its enterprise contracts.
Does Synthflow still offer self serve plans like Retell?
Not on its current pricing page, which lists enterprise contracts from $30,000 a year only. Retell's pay as you go plan has no monthly fee.