AI voice agents · Comparison
Best AI voice agent platforms (Retell, Vapi, Synthflow, Bland)
Updated 2026-09-20 · markdown mirror
Verdict
Retell is the sane starting point for AI voice: inbound and outbound, a visual builder, and per-minute pricing without a platform tax. Vapi is for engineering teams that want the raw controls. Synthflow is for agencies that refuse to touch an API. Bland is an outbound volume machine that happens to take calls.
The picks
- 01
Retell — best for most teams, inbound and outbound voice agents with a visual builder and per-minute pricing.
Don't use it if you need deep custom telephony control, you will hit the platform ceiling and want Vapi.
- 02
Vapi — best for engineering teams that want raw control over models, telephony, and latency.
Don't use it if you are not a developer, Vapi is API-first and expects you to write code.
- 03
Synthflow — best for agencies and non-coders building client voice agents without touching an API.
Don't use it if you need the cheapest per-minute rate at scale, compare minute pricing against Retell first.
- 04
Bland — best for high-volume outbound phone campaigns run by engineering teams.
Don't use it if you want a visual builder or inbound receptionist polish, Bland is an API with opinions.
| Tool | Free tier | Paid from | Inbound calls | Outbound campaigns | No-code builder | AI crawlers |
|---|---|---|---|---|---|---|
| Retell | $10 in free credits Documented at the source Checked 2026-09-20 www.retellai.com /pricing | $0/mo Documented at the source Checked 2026-09-20 www.retellai.com /pricing Usage-based per-minute pricing with free trial credits, confirm rates | Yes Unconfirmed — in the claim queue Checked 2026-09-20 www.retellai.com | Yes, phone campaigns Documented at the source Checked 2026-09-20 www.retellai.com | Yes, visual workflow builder Documented at the source Checked 2026-09-20 www.retellai.com | open Tested by us Checked 2026-09-20 /ai-voice-agents/benchmarks/ai-voice-agents-ai-crawler-access/ Our benchmark (n=4 tools × 3 runs) — methodology on the benchmark page |
| Vapi | $5 in free credits Documented at the source Checked 2026-09-20 vapi.ai /pricing | $0/mo Documented at the source Checked 2026-09-20 vapi.ai /pricing Usage-based per-minute platform fee on top of provider costs, confirm rates | Yes Unconfirmed — in the claim queue Checked 2026-09-20 vapi.ai | Yes Unconfirmed — in the claim queue Checked 2026-09-20 vapi.ai | Workflows dashboard, but API-first Unconfirmed — in the claim queue Checked 2026-09-20 vapi.ai | open Tested by us Checked 2026-09-20 /ai-voice-agents/benchmarks/ai-voice-agents-ai-crawler-access/ Our benchmark (n=4 tools × 3 runs) — methodology on the benchmark page |
| Synthflow | No free tier or trial mentioned on the pricing page Documented at the source Checked 2026-09-20 synthflow.ai /pricing | $29/mo Unconfirmed — in the claim queue Checked 2026-09-20 synthflow.ai /pricing Confirm current ladder and minute allowances | Yes Unconfirmed — in the claim queue Checked 2026-09-20 synthflow.ai | Yes, campaign dialling on plans Unconfirmed — in the claim queue Checked 2026-09-20 synthflow.ai | Yes, fully no-code flow builder Unconfirmed — in the claim queue Checked 2026-09-20 synthflow.ai | open Tested by us Checked 2026-09-20 /ai-voice-agents/benchmarks/ai-voice-agents-ai-crawler-access/ Our benchmark (n=4 tools × 3 runs) — methodology on the benchmark page |
| Bland | Trial credits, confirm terms Unconfirmed — in the claim queue Checked 2026-09-20 www.blandy.ai /pricing | $0/mo Unconfirmed — in the claim queue Checked 2026-09-20 www.blandy.ai /pricing Usage-based per-minute pricing, confirm rates | Yes Unconfirmed — in the claim queue Checked 2026-09-20 www.blandy.ai | Yes, built for volume dialling Unconfirmed — in the claim queue Checked 2026-09-20 www.blandy.ai | No, API and developer tooling Unconfirmed — in the claim queue Checked 2026-09-20 www.blandy.ai | unknown Tested by us Checked 2026-09-20 /ai-voice-agents/benchmarks/ai-voice-agents-ai-crawler-access/ Our benchmark (n=4 tools × 3 runs) — methodology on the benchmark page |
● tested by us · ● documented at the source · ● unconfirmed, queued in /confirm.txt — hover or tap a dot for the source and date
What this category actually sells
Strip the demos and every platform here sells three things: a voice pipeline (model, transcription, speech) that stays under human patience thresholds, a telephony layer that answers and dials, and a builder that decides whether your team ships in days or months. The first two have converged. The third is the whole comparison: visual builder (Retell, Synthflow), dashboard over an API (Vapi), or no builder at all (Bland).
Pricing, honestly
Voice pricing is quoted per minute and stacked: platform fee, model cost, telephony. That stacking is where surprises live, and where comparison sites go stale. We record platform pricing as dated claims, flag the ones hidden behind JavaScript or geo-pricing, and refuse to publish a per-minute total we have not verified end to end. The benchmark page covers something else that matters here: whether these vendors let answer engines read their pages at all.
Agency versus engineering
Pick by team shape, not feature grid. Agencies and SMBs want Synthflow or Retell, where a flow diagram is the product. Product and platform engineers will be happier in Vapi or Bland within a week, because the builder becomes the ceiling. Nobody should choose this category on a demo call’s audio quality: all four clear the bar.
What we did not test
We have not run latency benchmarks across carriers or measured transfer-to- human reliability, and both belong in this cluster’s benchmark roadmap. We did run the crawler-access test on the benchmark page: real data, honest n, published method.
FAQ
What is the best AI voice agent platform?
Retell for most teams; visual builder, inbound and outbound, usage-based pricing. Vapi for developers who want model and telephony control. Synthflow for no-code agencies. Bland for high-volume outbound by engineering teams.
How much do AI voice agents cost?
Most platforms charge per minute of call time, on top of the underlying model and telephony costs. Retell, Vapi, and Bland are usage-based with free trial credits; Synthflow starts around $29 a month. Per-minute rates move often; check the sourced numbers on each profile page.
Can an AI agent answer inbound customer calls?
Yes on all four platforms in this comparison. The differences are workflow (visual builder versus code), transfer quality to humans, and how the platform bills. Start with Retell's inbound templates if you want the shortest path.
Which voice AI platform works without coding?
Synthflow, fully no-code. Retell's visual builder covers most needs without code. Vapi expects developers, and Bland is an API.