Test numbers

Free SIP & VoIP test numbers.

Dial-in numbers you can call from any SIP endpoint or the PSTN to verify audio path, caller ID delivery, DTMF end-to-end, codec alignment, STIR/SHAKEN attestation, and fax negotiation. No signup, no rate limit - just dial. Exact DIDs are being provisioned; the numbers below are placeholders for now.

Available tests

ANI readback: Speaks back the calling number (P-Asserted-Identity if present, otherwise From)
Attestation readback: Announces attestation level (A / B / C), verstat result, origination identifier, and signing-cert issuer parsed from the inbound Identity header (RFC 8224 / ATIS-1000074).
Echo with 0.5-second delay: Echoes your audio back with a 0.5-second delay. Useful for one-way audio detection, round-trip media latency measurement, NAT/STUN troubleshooting, and DSP buffering issues.
1004 Hz reference tone: Continuous reference tone at −30 dBm0 (1004 Hz per Bellcore TR-NWT-001401 / ITU-T O.150) for codec level alignment, noise-floor measurement, and end-to-end audio path verification.
Real-time DTMF readback: Announces every DTMF digit you press and plays its tone back instantly. Works across RFC 4733 (telephone-event), SIP INFO, and in-band detection – good for end-to-end DTMF interop verification.
UTC time announcement (POPCORN): Plays the current UTC time – a quick sanity check during maintenance windows and late-night cutovers. Inspired by 767-2676 (POPCORN).
T.38 / T.30 faxback: Receives your fax negotiation (T.38 UDPTL or T.30 G.711 pass-through) and sends back a one-page reference TIFF. Capture the call on your end and drop the PCAP into the fax decoder to verify the round-trip.; Provided by OnlyFaxes.com - Send and receive faxes for free!

Need a SIP client to call these?

We have a free browser-based WebRTC softphone you can configure against your own SIP trunk or carrier and dial any of the numbers above from a tab. It's a generic SIP client - bring your own credentials.

Open the softphone

Pair these test numbers with the STIR/SHAKEN decoder to inspect the full PASSporT, the T.38 & T.30 fax decoder to verify faxback captures, or the SIP trace analyzer to debug any call that doesn't behave as expected.