Read an Intelligent Mail barcode
Type or paste the bars of a USPS Intelligent Mail barcode, or the digits printed with it, and you'll see the five fields it holds with a plain explanation of each. It all happens in your browser, so nothing you type leaves the page.
The fields show up here. If you don't have a barcode handy, try the example, which comes from USPS's barcode specification.
What the fields mean
Updated October 20, 2026. The decoding follows USPS's specification USPS-B-3200, and the service type names come from USPS's Service Type ID table of January 21, 2024.
The first 20 digits are the tracking code. The barcode ID is almost always 00 on a letter, the Service Type ID says which mail class and services the mailer asked for, the Mailer ID names the business behind the barcode, and the serial number tells one piece from the next. The routing code after them is the destination ZIP Code, sometimes with the ZIP+4 and a 2 digit delivery point. Our guide to the Intelligent Mail barcode explains how the fields work together and how one stamped letter gets a barcode that USPS reports on.
Questions
Where do I find the bars and the digits?
The bars sit just above the address or along the bottom right edge of the envelope. Some mailers also print the 20 to 31 digits in small type under or over the bars, and when they do, typing the digits is quicker.
How do I type the bars?
Read the bars from left to right and type one letter for each: F for a full bar that runs top to bottom, A for an ascender that rises above the middle, D for a descender that drops below it, and T for a tracker, which is only the short middle part. Spaces and line breaks are fine.
What if it says the check doesn't match?
Every Intelligent Mail barcode carries a check value, so one wrong letter makes the whole barcode fail instead of giving you wrong digits. Look again at the bars that are easy to confuse, such as an ascender and a full bar.
Does this tool send the barcode anywhere?
No. It runs in your browser and never sends what you type to us or to USPS, so you can use it offline once the page has loaded.
Can it make a barcode?
No. It only reads barcodes. A barcode that USPS reports on needs a Mailer ID, a serial and a checked address, and PigeonTrail makes those on its own server for each letter a seller prints.
Can I look up where the letter is?
No, because the barcode alone doesn't lead to its scans. They go to the owner of the Mailer ID through USPS Informed Visibility, so only that business, or a service working for it, can see them.
Want a barcode that tracks?
PigeonTrail prints a working Intelligent Mail barcode on every envelope you stamp, and your first 100 letters each month are free.