Voicemail Detection

When you’re running outbound voice agents, voicemails are a reality — but wasting time or missing opportunities because of them shouldn’t be.

Vapi’s updated voicemail detection system gives you faster, smarter, and more flexible handling of voicemail events, so you can keep your calls efficient, responsive, and professional.

Why Voicemail Detection Matters

Save time by avoiding long waits on unanswered calls.
Optimize costs by cutting down on wasted minutes.
Improve UX by ensuring your agent behaves naturally when encountering voicemail greetings.
Boost response rates by leaving cleaner, more intentional voicemail messages.

Today’s Detection Options

You can now choose between several detection methods — but not all are created equal:

Detection Method	Strengths	Weaknesses	Recommendation
Vapi (Recommended)	Fast, accurate, gracefully handles interruptions	None significant	✅ Strongly recommended
Google	Very good accuracy, reliable	Slightly longer detection time than Vapi	✅ Recommended
OpenAI	High accuracy, flexible phrasing	Higher cost	✅ Good option if budget allows
Twilio (legacy)	Very fast machine beep detection	Prone to false positives	⚠️ Use only in special cases
Vapi Voicemail Tool (legacy)	Keyword-based detection in transcription	Slow, context-dependent	⚠️ Use only if needed

New Default Behavior: Vapi Voicemail Detection

With Vapi Voicemail Detection, your assistant will:

Detect voicemail faster (often within the first few seconds of the call).
Handle real-time pickups gracefully — if a human picks up mid-voicemail, the agent will switch back naturally.
Interrupt the bot’s first message appropriately if voicemail is detected mid-sentence.
Minimize false positives by combining audio analysis (beeps) and transcription intelligence.

All three providers — Vapi, Google, and OpenAI — now support interruption handling and false positive protection.

How to Configure It

On the Assistants tab, you’ll find an updated Voicemail Detection section:

Vapi Voicemail Detection Configuration

You can choose your preferred detection provider:

Vapi (default)
Google
OpenAI
Twilio
Tool-based (legacy)

Advanced Configuration Options

For each detection method, you can fine-tune the following parameters:

Parameter	Description
Initial Detection Delay	How long to wait (in seconds) before starting voicemail detection
Detection Retry Interval	How frequently to check for voicemail (in seconds)
Max Detection Retries	Maximum number of detection attempts before stopping
Max Voicemail Message Wait	Maximum time to wait before leaving a message (even without beep detection)

These settings allow you to balance:

Speed (how quickly voicemail is detected)
Accuracy (reducing false positives)
Cost (fewer detection attempts = lower API costs)

How Vapi Detection Works

Vapi’s detection engine combines:

Gemini model-based detection (fast and highly accurate on common voicemail phrasing)
Twilio beep detection (optional, for faster reaction to voicemail system beeps)
Real-time call monitoring to react instantly if a human unexpectedly picks up
Continuous voicemail polling during early call stages (detecting voicemail faster without waiting for a full timeout)

This hybrid approach means less call delay, fewer mistakes, and a much more natural call experience.

By switching to Vapi’s new detection system, you’ll avoid the common pitfalls of older voicemail detection, while creating a faster, smarter, and more professional experience for your users.