Selecting the right fax API is not as straightforward a decision as one might like - there are a whole range of factors that need to be considered, some of which you may not even be aware of. We've put together a comprehensive list of them below in an effort to make your decision easier.
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| OUTBOUND FAXING | |||||||
|---|---|---|---|---|---|---|---|
| FEATURES | InterFAX | Concord | eFax | Hello Fax | Phaxio | Right Fax | Twilio |
| PCI DSS compliant for inbound and outbound fax | ✓ | ✗ | ✗ | ✗ | ✗ | Locally installed | ✗ |
| HIPAA compliant for inbound and outbound fax | ✓ | ✓ | ✗ | ✗ | ✓ | Locally installed | ✗ |
| GDPR-compliant | ✓ | ✗ | ✗ | ✗ | ✗ | Locally installed | ✗ |
| Fax-viewing portal | ✓ | ✗ | ✓ | ✓ | ✓ | ✗ | ✗ |
| Supported Interfaces for sending faxes | ✓ (SOAP, REST, SMTP, web) |
✓ (SOAP, SMTP) |
✓ (REST, SMTP, web) |
✓ (REST, SMTP, web) |
✗ (REST) |
✓ (SMTP, integration) |
✗ (REST) |
| Outbound fax storage | ✓ | ✓ | ✓ | ✗ | ✓ | ✓ | ✓ |
| Maximum number of recipients per outbound fax | 20,000 | Unlimited | 50 | 1 | 20 | Unlimited | 1 |
| Unlimited number of documents per outbound fax | ✓ | ✓ | ✗ (limited to 10) |
✓ | ✓ | ✓ | ✗ (limited to 1) |
| Faxable document types | All commonly used Windows files | All commonly used Windows files | All commonly used Windows files | All commonly used Windows files | Limited list of file types | All commonly used Windows files | |
| Outbound fax callback | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ | ✓ |
| Unlimited number of simultaneous outbound faxes | ✓ | ✓ | ✓ | ✓ | ✗ (one fax/sec) |
✗ (Based on number of channels connected) |
✗ (one fax/sec) |
| No restriction on outbound fax destinations | ✓ | ✓ | ✓ | ✗ (Specific list of destinations) |
✗ (Specific list of destinations) |
✗ (Based on local phone service) |
✗ (US and Canada only) |
| Call attempts upon failure | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ |
| Try before you buy | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ | ✓ |
| Allow outbound service without inbound number | ✓ | ✓ | ✗ | ✓ | ✓ | ✗ | ✗ |
| Intelligent Routing | ✓ | ✓ | ✗ | ✗ | ✓ | ✗ | ✗ |
| Throttle-free outbound faxes | ✓ | ✗ | ✗ | ✓ | ✓ | ✓ | ✗ |
| Search outbound faxes via API | ✓ | ✓ | ✓ | ✗ | ✓ | ✗ | ✗ |
| Allow submission of documents inline | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
✗ |
| INBOUND FAXING | |||||||
| FEATURES | InterFAX | Concord | eFax | Hello Fax | Phaxio | Right Fax | Twilio |
| Fax-viewing portal | ✓ | ✓ | ✓ | ✗ | ✓ | ✗ | ✗ |
| Supports multiple interfaces for receiving faxes | ✓ (SOAP, REST, SMTP) |
✓ (SOAP, SMTP) |
✓ (REST, SMTP) |
✗ (REST) |
✗ (REST) |
✓ (SMTP, integration) |
✗ (REST) |
| Unlimited storage duration of inbound faxes | ✓ | ✗ | ✓ | ✓ | ✓ | ✓ | ✗ |
| Inbound fax callback | ✓ | ✓ | ✗ | ✓ | ✓ | ✗ | ✓ |
| Try before you buy available | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ | ✓ |
| Search inbound faxes via API | ✓ | ✓ | ✗ | ✗ | ✓ | ✗ | ✗ |
| Faxes received automatically | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ |
| GENERAL FACTS | |||||||
| FEATURES | InterFAX | Concord | eFax | Hello Fax | Phaxio | Right Fax | Twilio |
| Account management API | ✓ | ✗ | ✗ | ✗ | ✗ | ✗ | ✗ |
| Pay as you go pricing | ✓ | ✓ | ✗ | ✗ | ✓ | ✗ | ✓ |
| Helper libraries in different languages | ✓ | ✗ | ✗ | ✗ | ✓ | ✗ | ✗ |
| API integrations with any account type | ✓ | ✓ | ✓ | ✗ | ✓ | ✓ | ✓ |
| Unlimited scalability | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ | ✗ |
| Free API service | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ |
| Developer documentation | ✓ | ✗ | ✓ | ✓ | ✓ | ✗ | ✓ |
| Code samples | ✓ | ✗ | ✗ | ✗ | ✓ | ✗ | ✓ |