*** description: A guide to assist customers migrating from v1 to v3 of the Fax API og:description: A guide to assist customers migrating from v1 to v3 of the Fax API --------------------- For clean Markdown of any page, append .md to the page URL. For a complete documentation index, see https://developers.hellosign.com/docs/guides/llms.txt. For full documentation content, see https://developers.hellosign.com/docs/guides/llms-full.txt. # Dropbox Fax API v3 This guide is for Dropbox Fax API developers currently using the v1 endpoints who want to learn about the changes between v1 and v3. Notable changes
## Corresponding Endpoints
Endpoint v1 v3
Send Fax POST /v1/Accounts/[ACCOUNT GUID]/Transmissions POST [/v3/fax/send](/api/fax/send)
Get Fax GET /v1/Accounts/[ACCOUNT GUID]/Transmissions/[TRANSMISSION GUID] GET [/v3/fax](/api/fax/get)
List All Faxes GET /v1/Accounts/[ACCOUNT GUID]/Transmissions GET [/v3/fax/list](/api/fax/list)
List Available Area Codes GET /v1/AreaCodes GET [/v3/fax_line/area_codes](/api/fax-line/area-code-get)
Purchase Fax Line POST /v1/Accounts/[ACCOUNT GUID]/FaxLine POST [/v3/fax_line/create](/api/fax-line/create)
List Fax Lines GET /v1/Accounts/[ACCOUNT GUID]/FaxLine GET [/v3/fax_line/list](/api/fax-line/list)
Delete Fax Line DELETE /v1/Accounts/[Account GUID]/FaxLines/[PHONE NUMBER] DELETE [/v3/fax_line/delete](/api/fax-line/delete)
## Additional Functionality New endpoints are available in v3 to allow for more flexibility with faxes and fax lines.
Endpoint v3
Download Fax Files POST [/v3/fax/files/\[FAX ID\]](/api/fax/files)
Delete Fax DELETE [/v3/fax/\[FAX ID\]](/api/fax/delete)
Get Fax Line GET [/v3/fax_line/](/api/fax-line/get)
Add User to Fax Line PUT [/v3/fax_line/add_user](/api/fax-line/add-user)
Remove Fax Line Access PUT [/v3/fax_line/remove_user](/api/fax-line/remove-user)
## Callbacks Inbound and outbound fax callbacks will continue to be POSTed to the set `DefaultInboundFaxCallbackUrl` and `DefaultOutboundFaxCallbackUrl`. Callbacks to these URLs will remain in the [v1 format](https://faq.hellosign.com/hc/en-us/articles/218532468-Can-you-give-me-an-example-of-a-callback-event). The updated structure will be POSTed to the v3 callback url settings that can be specified on the [API Settings](https://app.hellofax.com/home/myAccount?current_tab=api) page. These new settings have the same expectations as the Sign API and require the same response detailed in the [Events and Callbacks Walkthrough](/docs/guides/events-and-callbacks/walkthrough#responding-to-events). ![Fax API Callback URL Setting](https://files.buildwithfern.com/https://dropbox123432.docs.buildwithfern.com/304eb6a619e250bda96eb78697bc63502ba5307893ddd933b6e52bdcfbac1f7f/docs/fax/api-setting-callbacks.png) ### Example v3 Payload ```json { "transmission": { "test_mode": false, "signature_request_id": "", "title": "Example Title", "original_title": "Example Title", "message": "Please read", "metadata": {}, "created_at": 1738001529, "is_complete": false, "is_declined": false, "has_error": false, "files_url": "https://api.hellosign.com/apiapp_dev.php/v3/fax/files/9c2c7e8c2ed1839f75a9a0227ce2954b1d7c3407", "cc_email_addresses": [], "final_copy_uri": "/v3/transmission/final_copy/9c2c7e8c2ed1839f75a9a0227ce2954b1d7c3407", "template_ids": [], "custom_fields": [], "attachments": [], "response_data": [], "signatures": [] }, "event": { "event_time": "1738001529", "event_type": "fax_sent", "event_hash": "950d3bdf03a30d520dfa6ac51a952ff93fe3a4d9754dd1412b6aec36206c1e81", "event_metadata": { "reported_for_account_id": "63522885f9261e2b04eea043933ee7313eb674fd" } }, "account_guid": "63522885f9261e2b04eea043933ee7313eb674fd", "account_id": null, "client_id": null } ``` ### Event Names Here is a list of webhook events that can be sent to your Fax callback urls: | Event type | Description | | ------------------ | ------------------------------------------------------------------------ | | `fax_received` | An inbound fax was received | | `fax_sent` | The outbound fax was sent successfully | | `fax_on_hold` | The outbound fax was placed on hold | | `fax_busy` | The outbound fax received a busy signal from the recipient's fax line | | `fax_no_answer` | The outbound fax recipient fax line did not pick up | | `fax_disconnected` | The outbound fax recipient fax line disconnected before the fax was sent | | `fax_blacklisted` | The outbound fax recipient fax line is blocked or invalid | ## Data Faxes sent via the v1 API are not stored once the fax has been sent successfully and are unable to be viewed in the UI. Incoming faxes that are POSTed to your callback URL are available in the "Faxes" page. Using the v3 API, this setting can now be enabled or disabled on the [API Settings](https://app.hellofax.com/home/myAccount?current_tab=api) page. ![Fax API Delete Setting](https://files.buildwithfern.com/https://dropbox123432.docs.buildwithfern.com/32a7eca9d065ae2a51d8d15e2a9f1edbad4b894f7a96613a95b1e5cf087f5ed5/docs/fax/api-setting-delete-fax.png) ## Backwards compatability If you move to the new API Core subscription plan, you will be billed automatically at the end of the billing month based on your fax usage and number of additional fax lines. Users on the new API Core plan can access both the v1 and v3 endpoints. Users on the existing API Basic plan can only access the v1 endpoints.