Buy USPS postage with Apple Pay, Google Pay, or Bitcoin super-fast!
Buy USPS postage with Apple Pay, Google Pay, or Bitcoin super-fast!


General Questions

How does Stampnik work?

Stampnik lets anyone ship a package or envelope and pay securely with Apple Pay, Google Pay, Credit/Debit Card, or bitcoin. We currently support domestic shipping within the United States with USPS Priority, USPS Express, USPS Media Mail, USPS Parcel Post, and USPS First-Class mail services.

What is bitcoin?

Bitcoin is essentially digital money. It is similar to cash, except that Bitcoin not controlled by any central authority. All transactions are publicly listed in a ledger known as the blockchain. You can read more about bitcoin on Wikipedia.

Can you recommend a label printer?

All Stampnik labels should be printed at least 4" x 6" and be securely attached to your box or envelope. A dedicated label printer is handy if you are shipping multiple items a day. We can recommend the following models (✓ indicates that we have tested the printer)

How can I keep track of new Stampnik features and updates?

Here are a few ways to find out what we're up to:

How can I keep track of service issues or downtime?

We post downtime and other service issues to our @StampnikStatus Twitter account.

Payment & Refund Questions

I made a mistake on a label. How do I request a refund?

Please take a look at our refund policy page to understand how refunds are processed.

What payment methods can I use?

We support secure payments via Apple Pay, Google Pay, Credit/Debit Card, or bitcoin. Bitcoin payments are available for customers after an account review. To request a review, please contact us and mention "Enable Bitcoin checkouts".

Why is my bitcoin payment taking so long to confirm?

Our bitcoin checkout process relies on the blockchain network to confirm the transaction, though in some cases we accept 0-confirmation payments. Usually this takes less than a minute, but rarely this has taken an hour or more.

Label & Package Questions

What is the maximum weight I can ship in a USPS flat-rate package?

Domestic: flat-rate boxes allow up to 70 pounds & flat-rate envelopes allow up to 4 pounds

International: most flat-rate boxes and envelopes allow up to 4 pounds. Medium and Large flat-rate boxes allow up to 20 pounds.

When sealing a Flat Rate Box or Flat Rate Envelope, the container flaps must be able to close within the normal folds. Tape may be applied to the flaps and seams to reinforce the container; provided the design of the container is not enlarged by opening the sides and the container is not reconstructed in any way. More information about flat-rate packaging can be found on the USPS website.

Where can I get flat-rate boxes and envelopes?

You can pick up small quantities of envelopes and boxes at your local post office for free. If you need a large number of boxes or envelopes, please order free supplies from

What are the dimensions of flat-rate boxes and envelopes?

We support all USPS Priority and Express service flat-rate packages. Here are their inner dimensions:

  • Small Box - 8⅝" x 5⅜" x 1⅝"
  • Medium Box (top loading) - 11" x 8½" x 5½"
  • Medium Box (side loading) - 13⅝" x 11⅞" x 3⅜"
  • Large Box - 12" x 12" x 5½"
  • Large Board Game Box - 23-11/16" x 11¾" x 3"
  • Letter Envelope - 12½" x 9½"
  • Legal Envelope - 15" x 9½"
  • Small Envelope - 10" x 6"

For further information about flat-rate packaging, please visit the USPS flat-package info page

The USPS website doesn't show tracking status for my label. Is there a problem?

Our labels are generated by a 3rd party vendor and package data is sent to USPS throughout the day. This means that tracking data sometimes takes up to 24 hours to show up.

Why does the label sometimes swap the address lines?

This is a known issue that does not affect the deliverability of your package. Our label providers have assured us that this formatting is correct to USPS requirements. You can verify this formatting at the USPS website.

How do I schedule a pick-up for my package?

You can schedule free pick-ups during your regular mail delivery by using the USPS pick-up scheduler

Bulk Order / CSV Questions

How does the bulk uploader work?

Our bulk label tool allows you to purchase multiple labels at once using a list of addresses. Currently, all packages must have the same "From" address and package type, but we plan to remove these limitations in the future.

How do I format my CSV file?

Download our sample CSV file to see how we expect the list of recipients to be structured. Please note that the first line must include headings like "Name", "AddressLine1", etc so our service can understand how to generate your label.

Hazardous Materials (HAZMAT) Questions

Can I ship hazardous materials with Stampnik?

Generally, no. However, USPS does allow some types of hazardous materials (HAZMAT) using proper labeling and an appropriate service level. Some HAZMAT can only be sent by ground transportation (e.g. Lithium batteries).

Stampnik supports Lithium battery shipments using the USPS Ground Advantage service.

To learn more, visit USPS Hazmat shipping guidelines

Can I ship Lithium batteries with Stampnik?

Yes, using Ground Advantage service. We support packages that include lithium batteries that comply with USPS Lithium battery regulations.

You must select Package contains Lithium battery when purchasing a label.