US Currency Security Features: How to Detect Fake Dollar Bills

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You work hard for your money, so there’s nothing worse than being ripped off by receiving counterfeit money!

Fortunately, many security features in US currency can help you to tell the real ones from the fake.

Currency Paper

Real dollar bill “paper” is made from 100% rag material (75% cotton, 25% linen). It’s crisp, durable, and more likely to withstand humidity compared to normal paper. This special paper blend is made by Crane Co., and isn’t sold commercially.

The paper is refined numerous times to create its distinct yellowish-green tint. This color is difficult for counterfeiters to reproduce accurately.

Currency printed today has many colors printed on the front side, but the back is still green.

The paper also features blue and red fibers weaved into its fabric. Counterfeiters try to copy these by printing them, but if you look closely, the difference becomes obvious because the lines are on top, rather than being a part of the paper.

Printing and Ink

The printing process subjects the bills to a lot of pressure, making them very thin. Most counterfeit dollars would be thicker by comparison.

The Swiss company SICPA makes the ink used in US currency. It is a special type of ink called color-shifting ink or optically variable ink. It changes color depending on the angle of the viewer.

For example, the number on the lower right of a $20 note (which denotes the amount the bill represents) should look green when viewed head-on, and turn to black when viewed from the side.

The ink is also water-resistant, so if the bill got wet and the ink bled out, it’s a fake.

Authentic printing features raised ink, so flat lettering is a dead giveaway of fake notes. There are two processes for inking used in US currency:


A printing process that involves placing the ink below the surface. The design or lettering is etched into the surface, and the ink is rubbed into the grooves. The result is a thick, raised ink with a soft, feathered appearance.


Topography is a relief printing technique, so the lettering should be deeply indented into the paper, and the ink not very uniform.

Print Detail

The inking can be very fine in some areas. Commercial printers are unable to reproduce this quality, so the fake bills tend to be blurry in comparison. Some areas to look out for include:


The outside border of real dollar bills features a recurrent pattern. It should be clean and unbroken, with no sign of ink bleeding.

The Federal Reserve and Treasury seals have pointed borders. These should be sharp and even.


Real dollar bills have sharp, fine detailing on the portraits. The portrait also stands out from the background. The fake bills would be too blurry and the ink tends to bleed into the background.

Use a magnifying glass to observe the rim around the portrait. The detailing should read “THE UNITED STATES OF AMERICA” in a very tiny font.

There’s microprinting in various other locations, but it’s hard to see with the naked eye. For example, the denomination number at the bottom of the bill would have the number spelled out multiple times. Normally, it just looks like horizontal lines.

Security Thread

Vertical security threads (or plastic strips) are sewn into $5, $10, $20, $50, and $100 notes. They’re always at the same spot for each denomination.

For example, all 5$ bills will have the thread in the same exact spot. You can see this thread simply by holding the bill up in front of a light source.

Interestingly, the security thread glows in a specific color when ultraviolet light is cast on it, based on denomination. The colors should be as follows:

DenominationSecurity Thread Color

The point of having a different color for each denomination is to prevent counterfeiters from bleaching out the ink on a lower value bill, and replacing it with a higher one.


The watermark differs based on denomination, as it’s a copy of the portrait on each.

Tiny variations in the density of the paper are purposely created during the paper refining process. When light shines through, it creates different color tones.

You can only see the full image by holding the bill up to a light source. For example, a new $100 bill would have an image of Ben Franklin. You can see this portrait on both sides of the bill.


If you’re ever unsure if the bill you have in your hand is real or fake, follow this checklist:

  • Compare the suspicious bill with another one of the same denomination
  • Feel the texture of the paper and ink. The paper should be crisp and the ink should be raised or indented
  • Examine the quality of printing, especially in areas with fine details such as the portrait and borders
  • Use a black light to determine the location and color of the security thread (if it’s a 5$ bills or higher).

It’s important to give any fake money you come across to the authorities. If possible, try to remember who gave it to you. They may be a counterfeiter themselves or they may also be a victim. Either way, the information will help the authorities investigate.

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Hi, I'm GP. A personal finance expert with a mission to help Entirely Money readers break free of money worries. Combining a finance-focused education background (B.S. in Finance and MBA with Finance focus) with over 15 years of personal and corporate finance experience to help you achieve your financial best life!