A fax API is a set of REST endpoints that lets your application send and receive faxes programmatically. You make an HTTP request with a document and a phone number, and the provider's infrastructure handles the analog transmission. No fax machine or phone line required. See our [cloud fax guide](/blog/cloud-fax/) for how the underlying technology works.

How much does a fax API cost?

Fax API pricing ranges from $0.007 to $0.10 per page depending on the provider, plus $0.94–$2.00/mo per fax number. Some providers offer bundled plans starting at $8–$25/mo. mFax Business plans start at $20.99/mo with API access and HIPAA compliance included.

Is fax API HIPAA compliant?

Yes — if the provider offers TLS 1.2+ encryption, AES-256 at rest, a signed Business Associate Agreement (BAA), and audit logging. Not every fax API qualifies. See our [HIPAA compliant fax guide](/blog/hipaa-compliant-fax/) for the full checklist.

Does Twilio still have a fax API?

Twilio deprecated its original Programmable Fax in December 2021. A newer outbound-only version is available but inbound remains in beta. Alternatives like Telnyx, Sinch, and mFax offer more complete fax API solutions in 2026.

What file formats do fax APIs support?

Most fax APIs accept PDF, DOC/DOCX, TIFF, JPG, PNG, XLS/XLSX, RTF, TXT, and HTML. The provider converts everything to TIFF (the native fax format) server-side before transmission. RingCentral supports up to 29 formats.

Fax API: How to Send Faxes Programmatically (2026)

A fax API lets developers send and receive faxes through simple REST calls — no fax machine, no phone line, no protocol knowledge. Learn how fax APIs work, compare providers and pricing, and integrate faxing into your app.

Frequently Asked Questions

What is a fax API?: A fax API is a set of REST endpoints that lets your application send and receive faxes programmatically. You make an HTTP request with a document and a phone number, and the provider's infrastructure handles the analog transmission. No fax machine or phone line required. See our [cloud fax guide](/blog/cloud-fax/) for how the underlying technology works.
How much does a fax API cost?: Fax API pricing ranges from $0.007 to $0.10 per page depending on the provider, plus $0.94–$2.00/mo per fax number. Some providers offer bundled plans starting at $8–$25/mo. mFax Business plans start at $20.99/mo with API access and HIPAA compliance included.
Is fax API HIPAA compliant?: Yes — if the provider offers TLS 1.2+ encryption, AES-256 at rest, a signed Business Associate Agreement (BAA), and audit logging. Not every fax API qualifies. See our [HIPAA compliant fax guide](/blog/hipaa-compliant-fax/) for the full checklist.
Does Twilio still have a fax API?: Twilio deprecated its original Programmable Fax in December 2021. A newer outbound-only version is available but inbound remains in beta. Alternatives like Telnyx, Sinch, and mFax offer more complete fax API solutions in 2026.
What file formats do fax APIs support?: Most fax APIs accept PDF, DOC/DOCX, TIFF, JPG, PNG, XLS/XLSX, RTF, TXT, and HTML. The provider converts everything to TIFF (the native fax format) server-side before transmission. RingCentral supports up to 29 formats.