← All AI customer support software

Retell AI vs Synthflow (2026)

Comparing Retell AI and Synthflow? Both are AI Agents & Chatbots and Voice & Phone AI tools in the directory, which is why buyers put them on the same shortlist. Below is a side-by-side look at pricing and an estimated monthly bill, channels, compliance claims, and integrations, plus when each is the better fit, so you can pick on the facts rather than either vendor's own sales page.

At a glance

Conversations/mo

% handled by AI

Agent seats

Price it at my volume

Estimates assume 5,000 conversations a month, 60% handled by AI and 10 agent seats, at each vendor's published list price (the cost calculator's model); treat them as a floor, not a quote. Compliance rows are what vendors publicly claim, and “Not verified” means we have not confirmed that fact yet, not that the tool lacks it.

Choose Retell AI or Synthflow?

About Retell AI

Retell AI is a platform for building AI phone agents that answer and place calls. You compose an agent from interchangeable parts: a speech-to-text layer, your choice of LLM, a voice from providers like ElevenLabs, and telephony via Twilio, Vonage, Telnyx, or your own SIP trunk. The platform handles the hard real time bits, interruption handling, latency, call transfer, and IVR navigation, and adds testing, monitoring, and post call analysis aimed squarely at contact center and front desk workloads.

The company came out of Y Combinator's Winter 2024 batch, founded in 2023, with Evie Wang among the cofounders. It grew unusually fast for a seed stage company: a $4.6 million seed led by Alt Capital in September 2024 arrived alongside a reported $3 million in annual revenue within months of launch. Named customers include telehealth company Ro, plus BPOs and contact center operators.

Pricing is published and usage based, which is refreshingly rare. Retell quotes $0.07 to $0.31 per minute all in, depending on your voice and model choices, with components itemized: text-to-speech from $0.015 per minute, LLM costs from $0.003 to $0.16 per minute, US telephony around $0.015 per minute. Every account includes 20 concurrent calls, extra concurrency is $8 per line monthly, phone numbers cost $2 monthly, and new accounts get $10 in free credits. Enterprise plans with dedicated infrastructure are custom.

Choose Retell if you have some technical ability, want a working phone agent this week, and value published per minute economics you can model before committing. Its contact center tilt (batch calling, warm transfer, IVR traversal) makes it a natural fit for support lines. Look elsewhere if you want a fully managed enterprise deployment with a vendor doing the tuning, or a pure no-code experience for a non-technical team.

Read the full Retell AI listing →  ·  See Retell AI alternatives →

About Synthflow

Synthflow is a platform for building AI voice agents that answer and place phone calls, and since 2026 it also runs chat agents from the same workflows. Agents are built in a visual Flow Designer, where subflows act as specialised agents for separate tasks and steps call your APIs, and are deployed into customer service, receptionist, appointment booking, IVR, lead qualification and outbound campaigns. It connects to more than 200 tools, including contact center platforms (Genesys, Five9, 8x8, RingCentral, Cisco, Avaya), CRMs (Salesforce, HubSpot, Zoho, Freshworks), helpdesks (Zendesk, Intercom) and telephony carriers such as Twilio, Telnyx and Vonage. Synthflow claims more than 30 languages.

Two things distinguish it from Retell and Vapi, the developer-first voice platforms it is usually compared with. First, Synthflow runs its own telephony network, which it says keeps latency under 100 milliseconds and lets it place voice infrastructure in the regions a customer needs, while still accepting your own carrier or SIP trunk. Second, it has packaged the agent lifecycle into what it calls the BELL framework (Build, Evaluate, Launch, Learn): agents are tested in a Test Center with simulated calls before going live, and Auto-QA scores every live conversation afterwards so the results feed the next version. Forward-deployed engineers handle enterprise rollouts. The trust center lists SOC 2 Type 2, ISO 27001, ISO 42001, HIPAA, PCI DSS, GDPR and EU AI Act coverage, which is unusually broad for a company this young.

Synthflow was founded in Berlin in 2023 by Hakob Astabatsyan (CEO), Albert Astabatsyan and Sassun Mirzakhan-Saky. It raised a pre-seed led by Atlantic Labs, a seed led by Singular in 2024 and a $20 million Series A led by Accel in June 2025, for $30 million in total, and has about 70 employees. It says more than 130 enterprises use it. The most notable deployment is a partnership with Freshworks that puts Synthflow voice AI inside Freshcaller, Freshdesk and Freshservice, automating up to 65 percent of routine voice requests; 8x8 and AVANT signed channel partnerships in 2026. Customer stories include Thryv, Medbelle, Euro Paper and Niagara Region Transit.

Synthflow has moved upmarket: its pricing page now lists only enterprise contracts, starting at $30,000 a year and scoped around call volume, concurrency, telephony and integrations. Choose Synthflow if you want enterprise voice agents with telephony, testing and QA handled by one vendor, especially if you already run Freshworks or 8x8. Skip it if you are a small business or developer wanting to pay by the minute and build yourself; Retell or Vapi publish usage pricing and let you start without a contract.

Read the full Synthflow listing →  ·  See Synthflow alternatives →

Know when Retell AI or Synthflow changes

One plain-text email at the start of each month with every verified price change, acquisition and new listing across the directory, including any change to Retell AI or Synthflow. No tracking pixels, unsubscribe in one click.

Email

Website

Subscribe