The one-line difference: First-Class sends a letter. Certified sends a letter you can **prove** arrived.

* **First-Class ($4.99)** is right for everyday letters — thank-yous, requests, notes, inquiries. Regular letter delivery, no tracking.

* **Certified Mail ($14.99)** adds:

  * A **USPS tracking number**, so you can follow the letter.

  * A **USPS record of delivery** to the recipient's address (electronic delivery confirmation — not a signature).

Pick Certified when it may matter later that the letter arrived — disputes, official notices, deadlines, or anything you might need on the record. If you need a verifiable record of when a letter was sent or delivered, Certified is the only option that provides one; no such proof is available for First-Class.

Both travel at about the same speed — Certified is about proof, not speed. You choose the mail class on the Preview & pay step, right before checkout.