List of common Twilio Errors

Network Conditions¶

Local network conditions have the biggest impact on voice quality. Jitter, latency, and packet loss can be the biggest contributors to voice quality issues in any VoIP network.


Latency	The time it takes the RTP (media) packets to arrive at the destination	Causes media delivery delays, callers may speak over the top of each other.
Packet loss	Packets that don't make it to the final destination	Causes gaps and cut-outs in media, callers may not hear the other side.
Jitter	Packets that arrive at the destination out of order	Cause a ‘robotic’ distortion effect in media, or packet loss when overrunning the jitter buffer

From https://support.twilio.com/hc/en-us/articles/223180908-How-do-I-troubleshoot-common-problems-with-Twilio-Client-

Latency: High latency can substantially degrade a caller's experience. While there will always be some latency between the codec algorithm, the jitter buffer, and network traversal, the goal is to keep this to a minimum. Callers typically start to notice the effect of latency once it breaches 250ms, and find latency above ~600ms to be nearly unusable. Here are some strategies to minimize latency on your network:

Some lower bandwidth fixed internet connections can often have a higher latency. If possible, upgrade your internet connectivity.
Stick to high-bandwidth connections. Mobile networks such as LTE (mobile 4G Data) can often have high latency.
Ensure you’re using Twilio Client 1.3 or higher to take advantage of Twilio’s Global Low Latency routing infrastructure.

Jitter: Packet loss, most frequently jitter-induced packet loss, can make a big impact on your VoIP call quality. Wi-Fi can be particularly bad for creating jitter. Here are some strategies to minimize jitter on your network:

Use fixed ethernet instead of Wi-Fi whenever possible
Reduce packet conflicts on Wi-Fi by reducing the number of devices operating on the same channel.
Avoid large data file transfers over the same Wi-Fi environment concurrently with voice.
Avoid bufferbloat, which can result in high latency, and bursts of jitter. We recommend ensuring your router is configured with a low buffer size, as high jitter cannot be masked by a buffer without introducing artificial delay, and often choppy audio.
Note: Not all routers allow for configuring buffer sizes, but some routers ship with defaults which are not optimized for real time VoIP networks. Open source routers, enterprise grade routers and gamer-oriented routers are good candidates for providing the right configuration options and defaults.

If you have addressed the above issues and continue to have jitter related impact on your voice quality, you may consider configuring your router with QoS rules to prioritize traffic on the above media UDP ports. Given the large range of UDP ports you should only do this with prior consideration to what other traffic may be flowing in that port range.

Twilio Client cannot establish a call¶

Check open network ports in your router / firewall / antivirus software
Confirm a network connection is currently available
Review the javascript console for application errors

No audio or one-way audio¶

Check open network ports in your router / firewall / antivirus software
Confirm the hardware is correctly attached and ensure the correct microphone and speakers are selected in software settings
Check to ensure the microphone is not muted (some have a hardware mute button) and the speaker volume is turned up

Call audio cutting out or stops transmitting¶

Twilio Client requires a high speed and low latency network connection. Benchmark the network by testing your throughput and ping at speedtest.net and aim to improve the scores.
Enable router QoS or prioritize traffic for Twilio Client
Reduce network activity not related to VoIP or use a separate network for VoIP workstations

Call audio is garbled or contains artifacts¶

Use a headset instead of built in computer microphone
Reduce ambient noise such as nearby speakers or fans
Adjust the distance of the microphone from the mouth - too close can cause audio clipping
Adjust microphone levels in the computer’s sound settings
Ensure computer has resources available to process a call
CPU and RAM are not over-utilized
Close un-needed applications and browser tabs
Try disabling antivirus software

Microphone level is changing on its own¶

Some device drivers do not behave properly for auto-gain control. For the complete list of audioConstraints, please refer to the FAQ How to constrain the audio sources in Google Chrome?

Choppy or Robotic Sounding Call Audio¶

When call audio has a robotic-sound or choppy cuts in and out, this is often caused by packet loss due to excessive jitter on the line. Jitter is the term used when packets are received out-of-order, and can be caused by a number of factors including network traffic, or the technologies used in the call.

For help troubleshooting audio issues caused by jitter, please see Troubleshooting Call Audio Jitter Issues on Twilio Programmable Voice Calls.

One-way or Missing Call Audio¶

When a caller can hear the other party, but the other party can't hear the caller, we refer to this as one-way audio. Missing audio streams can be caused by a number of factors including errors in the connection/handshake, problems during a network handoff, or issues at the source or destination.

For help troubleshooting audio issues caused by one-way audio, please see Troubleshooting One-Way Audio Issues on Twilio Programmable Voice Calls.

Delayed Call Audio¶

When caller or callee reports excessive delays in the call audio, this is often caused by excessive latency on the line. Call audio latency can be caused by a number of factors including delayed packet transmission or delivery somewhere along the line, or the technologies used in the call.

For help troubleshooting audio issues caused by latency, please see Troubleshooting Latency and Delayed Audio Issues on Twilio Programmable Voice Calls.

Call Audio Echoing¶

When a caller or callee reports that they hear their own delayed audio being transmitted back to them, we refer to this as call audio echo. Echo is often caused by positioning and volume levels of the speaker and microphone at one end of the line, or by crosstalk on copper wire (landline) networks.

Positioning and volume adjustment¶

Most audio echo issues are caused by one callee or caller's microphone picking up the audio coming from the speaker, and then transmitting it back through the call. Please run through this troubleshooting checklist to try and resolve this issue:

Disable any speakerphone functionality, and instead use a headset or a phone handset.
If using a computer with speakers and a separate microphone, use a headset or phone handset instead.
Lower the output volume on the speaker or handset.
If using a separate microphone, point it away from any speakers where call audio is outputting, and point it towards the caller or callee.

If the above adjustments do not help resolve this issue, continue reading for additional troubleshooting https://support.twilio.com/hc/en-us/articles/360022008913-Troubleshooting-Call-Audio-Echo-Issues-Twilio-Programmable-Voice-Calls

Call Volume Issues¶

When a caller or callee reports that the volume of a call is either too loud or too quiet, we typically classify this as a call audio volume issue. These call volume issues are often caused by the hardware used, including the positioning and levels of the speaker and/or microphone at one end of the line.

For help troubleshooting audio volume issues, please see Troubleshooting Call Audio Volume Issues Twilio Programmable Voice Calls.

Call Static¶

When a caller or callee reports audio interference or background noise on a call, we typically classify this as a call audio static issue. These audio quality issues are often caused by the hardware used, including the placement, positioning, and levels of the speaker and/or microphone at one end of the line.

For help troubleshooting audio issues caused by static, please see Troubleshooting Call Audio Static Issues Twilio Programmable Voice Calls.

Failed or Unsuccessful API Call Requests¶

If you aren't seeing a record of your call, then there was likely an incident, or an issue with with your API request. Try attempting to place your call again https://support.twilio.com/hc/en-us/articles/360009804954-Simple-Example-for-Placing-Programmable-Voice-Calls, and check for similar results.

When Twilio receives an invalid API request, we return a 400 Bad Request response, along with a secondary 5-digit error code, and a message explaining what the issue is. Here are the most common problems we see for outbound voice calls:

Error	Issue	Troubleshooting
`10001`	Invalid credentials	Verify your project has an active balance by logging into Console, and that your request is using the correct Account SID and Auth Token.
`20003`	Invalid credentials	Verify your project has an active balance by logging into Console, and that your request is using the correct Account SID and Auth Token.
`20005`	Invalid credentials	Verify your project has an active balance by logging into Console, and that your request is using the correct Account SID and Auth Token.
`21203`	Destination is not allowed	You need to enable calling to this destination in Geo Permissions.
`21215`	Destination is not allowed	You need to enable calling to this destination in Geo Permissions.
`32205`	Destination is not allowed	You need to enable calling to this destination in Geo Permissions.
`21210`	From phone number is missing or invalid	Verify your request has a valid Twilio phone number on your project, or a verified non-Twilio caller ID in the From parameter, with proper E.164 formatting.
`21212`	From phone number is missing or invalid	Verify your request has a valid Twilio phone number on your project, or a verified non-Twilio caller ID in the From parameter, with proper E.164 formatting.
`21213`	From phone number is missing or invalid	Verify your request has a valid Twilio phone number on your project, or a verified non-Twilio caller ID in the From parameter, with proper E.164 formatting.
`21201`	To phone number is missing or not supported	Verify your request has a non-premium or shared cost phone number in the To parameter, with proper E.164 formatting.
`21202`	To phone number is missing or not supported	Verify your request has a non-premium or shared cost phone number in the To parameter, with proper E.164 formatting.
`21211`	To phone number is missing or not supported	Verify your request has a non-premium or shared cost phone number in the To parameter, with proper E.164 formatting.
`21214`	To phone number is invalid or can't be reached	Verify your request has a valid phone number in the To parameter, with proper E.164 formatting.
`21217`	To phone number is invalid or can't be reached	Verify your request has a valid phone number in the To parameter, with proper E.164 formatting.

If your error is not listed here, you can find the list of 2XXXX REST API errors along with instructions for resolving these issues in our API Errors and Warnings Dictionary https://www.twilio.com/docs/api/errors#2-anchor.