Documentation Index
Fetch the complete documentation index at: https://mintfax.com/docs/llms.txt
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Can I receive faxes through mintfax?
No. mintfax is an outbound fax API. You send faxes through the API; there is no inbound fax number or receive endpoint.Do I need a fax number to send?
No. You provide the destination number and the document, and mintfax handles delivery. No dedicated fax number or hardware required.What file formats can I send?
PDF, DOCX, XLSX, JPG, PNG, TIFF, HTML, and TXT. Maximum file size is 10 MB. PDF is recommended for the most predictable rendering. See file types and sizes for conversion notes and edge cases.How long does a fax take to deliver?
Most faxes complete in 1-5 minutes depending on page count and destination line quality. The analog phone leg is the bottleneck, not the API. See time-sensitive documents for tips on optimizing delivery speed.How do I know if a fax was delivered?
PollGET /fax/{id} for the status, or register a webhook endpoint to receive fax.delivered and fax.failed events in real time. See track delivery for both approaches with code samples.
What happens if the destination line is busy?
mintfax retries automatically. The default is 3 retries, configurable up to 10 per fax or as a workspace default. Each retry fires afax.retry_scheduled webhook event. If all retries are exhausted, the fax moves to failed and the credit hold is released.
Can I resend a failed fax?
Yes.POST /fax/{id}/resend resubmits the original document as a new fax. A new credit hold is placed. The original document must still be within the retention window.
Are there ads or branding on the faxes I send?
No. Faxes contain only your document and optional cover page. mintfax does not add advertisements, logos, or branding of any kind.How much does a fax cost?
Credits are prepaid and charged per page. Check your current balance withGET /account/balance. See credits and billing for the hold lifecycle and balance monitoring.
Are there monthly minimums, setup fees, or contracts?
No. There are no monthly fees, no setup costs, and no long-term contracts. You buy credits when you need them and use them at your own pace. Cancel anytime.Can my account recharge automatically?
Yes. Enable auto top-up in the dashboard to add credits automatically when your balance drops below a threshold you set. Thebalance.low webhook event fires at the same threshold if you want to handle it programmatically.
What payment methods do you accept?
Visa, Mastercard, American Express, and Discover. Payments are processed through Stripe.What is the difference between sandbox and live?
Two completely isolated environments. Sandbox keys (fx_test_) route to simulated infrastructure with magic fax numbers that produce deterministic outcomes. Live keys (fx_live_) send real faxes. The API surface is identical. See environments.
Can I test without sending real faxes?
Yes. The sandbox provides magic numbers that simulate success, busy, transient failure, permanent failure, and insufficient balance. No real fax is sent and no real money is spent.Is there an SDK?
A Node.js SDK is available. For other languages, call the REST API directly. The API uses standard Bearer auth and multipart/form-data for file uploads.How do I handle errors?
Every error returns a consistent JSON envelope with a stableerror code, a human-readable message, and an action hint. Match on the error field, not the HTTP status or message text. See the error catalog for every code and recommended action.
What happens if my webhook endpoint is down?
mintfax retries failed webhook deliveries with exponential backoff. Your endpoint should respond within 5 seconds. Useevent_id for deduplication since retries may deliver the same event more than once. See webhooks.