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sinch-fax-api

Send, receive, and manage faxes programmatically via the Sinch Fax API.

9|4|Updated Jan 29, 2026
Search Tags:#api#legal#webhook#healthcare#fax#fax-to-email#cover-pages
One-click install
npx skills add https://github.com/sinch/skills --skill sinch-fax-api
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: sinch-fax-api
Source: https://github.com/sinch/skills/tree/main/skills/sinch-fax-api
Command: npx skills add https://github.com/sinch/skills --skill sinch-fax-api

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Sinch Fax API lets you send and receive faxes programmatically. It supports multiple file formats, webhooks for incoming faxes, fax-to-email delivery, and automatic retries. Used for healthcare, legal, financial, and government applications where fax remains a required communication channel.

Core Features & Use Cases

  • Fax Services — Logical containers for fax configuration. Associate numbers, set defaults, and manage routing.
  • Fax Numbers — Phone numbers provisioned for fax. Must be configured in your Sinch dashboard.
  • Faxes — Individual fax transmissions (inbound or outbound). Each has a unique ID, status, and metadata.
  • Fax statuses — QUEUED → IN_PROGRESS → COMPLETED or FAILURE. Error details in errorType and errorMessage fields.
  • Supported formats — PDF (most reliable), DOC, DOCX, TIF/TIFF, JPG, PNG, TXT, HTML.
  • Webhooks/Callbacks — HTTP POST notifications for fax events. Default content type is multipart/form-data (fax content as attachment).
  • Cover Pages — Customizable cover pages per service. Attach via coverPageId and coverPageData on send.
  • Fax-to-Email — Incoming faxes auto-forwarded to configured email.
  • Retries — Auto-retry on failure. Default set per fax service; maximum: 5.
  • Retention — Fax logs and media retained for 13 months. Use DELETE /faxes/{id}/file to remove earlier.

Quick Start

Configure a fax service and send a test fax using a sample contentUrl via Node.js SDK or REST API.

Frequently Asked Questions about sinch-fax-api

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I send a fax programmatically using an API?▼

You can send faxes programmatically by calling the fax API with a contentUrl or file attachment. The Sinch Fax API supports formats like PDF, DOCX, and TIFF, handling the transmission automatically with configurable retries and cover pages.

Can I receive incoming faxes via webhook automatically?▼

Yes, incoming faxes trigger HTTP POST webhook callbacks automatically. The default content type is multipart/form-data with the fax content attached, allowing your server to process incoming fax transmissions instantly without polling.

What file formats are supported for sending faxes through an API?▼

Supported file formats include PDF, DOC, DOCX, TIF/TIFF, JPG, PNG, TXT, and HTML. PDF is the most reliable format for fax transmissions, ensuring consistent rendering across all outbound fax services.

Does the fax API support automatic retries for failed transmissions?▼

Yes, the fax API supports automatic retries on failure. Default retry settings are configured per fax service, with a maximum of five retry attempts for each failed outbound fax transmission.

How do I manage fax retention and delete fax logs?▼

Fax logs and media are retained for 13 months by default. You can remove fax media earlier by sending a DELETE request to the specific fax ID file endpoint, controlling your data retention compliance.

Is there a way to configure fax-to-email forwarding for incoming faxes?▼

Yes, fax-to-email forwarding automatically sends incoming faxes to a configured email address. This feature routes inbound fax transmissions directly to your inbox without requiring additional webhook or server setup.

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