Send a Fax via API

The Telnyx Programmable Fax API lets you send, receive, and manage faxes through a set of easy-to-use HTTP endpoints.

In this guide, you'll learn how to send a fax using the Programmable Fax API in four simple steps.

First, follow our Quickstart guide to create a Telnyx account, phone number, and Fax Application.

If you already have a Telnyx V2 API Authentication key, skip to Step 3.

1. In the Telnyx Mission Control Portal , in the left menu bar navigate to " API Keys ".
2. Ensure, API V2 is selected in the horizontal menu bar.
3. Click "Create API key"
4. Copy the API key and save it somewhere safe.

The Telnyx Programmable Fax API supports PDF files. To initiate sending a fax, we need to send the request to the Telnyx Programmable Fax API endpoint https://api.telnyx.com/v2/faxes.

We need to send additional parameters containing authentication information with the request, so Telnyx knows which account to send the fax from and information about the destination and file being sent.

Header	Description
media_url	The URL of the PDF used for the fax's media.
connection_id	The app ID or connection ID to send the fax with.
to	The fax enabled phone number (in E.164 format), or SIP URI, the fax will be sent to.
from	The phone number, in E.164 format, the fax will be sent from.
Authorizaton: Bearer	The prefix to your API V2 key created in Step 2.

Now that we know what we need to include in our request, we can use a number of different methods to structure and send it. In this example, we are going to use curl straight from the command line. You can also use a client such as Postman to structure your request.

curl -X POST https://api.telnyx.com/v2/faxes \
--data-urlencode "media_url=https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf" \
--data-urlencode "connection_id=1232154810234" \
--data-urlencode "to=+13129457420" \
--data-urlencode "from=+19459457421" \
--header "Authorization: Bearer APIAuthKey_fromPortal"

Note

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Simply copy the above code into your favorite text editor, paste in your parameters from the table in place of the existing data, and execute the command.

If you have successfully structured your command and the fax has begun sending, the Programmable Fax API will respond with HTTP 202.

If you do not receive a HTTP 202 response, double-check your request and try again. Explanations of other response codes can be found in our API reference.

Once the request to send the fax has been successfullly received by Telnyx, you should begin receiving a series of webhooks to the URL that you specified in your Fax Application.

The webhooks you should receive are:

• fax.queued
• fax.media.processed
• fax.sending.started
• fax.delivered
• fax.failed

That's it! Once you've received a fax.delivered webhook, your fax has been delivered to its destinaion.

{
  "event_type": "fax.delivered",
  "id": "3320554f-6b74-4138-a74b-a1e2ec7eaf8b",
  "occurred_at": "2022-01-07T10:01:43.677850Z",
  "payload": {
    "call_duration_secs": 79,
    "connection_id": "1232154810234",
    "direction": "outbound",
    "fax_id": "c62be5bc-9b13-4b6c-abda-34dd8b541287",
    "from": "+19459457421",
    "original_media_url": "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf",
    "page_count": 1,
    "status": "delivered",
    "to": "+13129457420",
    "user_id": "bdaa1f9f-1018-4156-867d-6c4ac9f556eb"
  }
}

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{
  "event_type": "fax.failed",
  "id": "d906ecda-db21-428e-9ca0-74dae7e7c144",
  "occurred_at": "2022-01-05T22:23:46.888808Z",
  "payload": {
    "connection_id": "1232154810234",
    "direction": "outbound",
    "failure_reason": "user_busy",
    "fax_id": "f7b303ed-674c-4962-951b-848380510893",
    "from": "+19459457421",
    "original_media_url": "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf",
    "status": "failed",
    "to": "+13129457420",
    "user_id": "417b0cc2-39e0-4ab9-b116-e56543649aa9"
  }
}

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Inspect the failure_reason field in webhook's payload to debug failed deliveries of your faxes. The possible failure reasons are:

• account_disabled
• connection_channel_limit_exceeded
• destination_invalid
• destination_not_in_countries_whitelist
• destination_not_in_service_plan
• destination_unreachable
• fax_signaling_error
• invalid_ecm_response_from_receiver
• no_outbound_profile
• outbound_profile_channel_limit_exceeded
• outbound_profile_daily_spend_limit_exceeded
• receiver_call_dropped
• receiver_communication_error
• receiver_decline
• receiver_incompatible_destination
• receiver_invalid_number_format
• receiver_no_answer
• receiver_no_response
• receiver_recovery_on_timer_expire
• receiver_unallocated_number
• service_unavailable
• user_busy
• user_channel_limit_exceeded

Continue to our next tutorial to learn how to receive inbound faxes via API.