Identity industry

February 10, 2021

First-line verification and second-line checks of passports – what’s the difference?

The sprint and marathon ways of verifying a passport – compared and explained by our expert.

Verifying identity documents is like running – you can run a sprint, but also a marathon. Both are the same movement, but their speed and duration are entirely different.

Think of this metaphor to better understand ID verification. Think of first-line verification as a sprint, and second-line authentication as a long-distance run. In this article, we show you why these two different concepts exist and what kind of security checks are used.

The anatomy of an ID

To see the depths of ID verification, you should start with the ID itself. Its key function is to hold data of the owner and of the document itself – however, all these data are subject to forgeries and alterations. It has to be protected.

That’s why an ID is full of security marks, prints, patterns, holograms: these are all features that protect the genuineness of identification documents and avoid copying and forging them. When checking IDs, these features play a great role.

This happens when your ID is checked

When forgery experts are verifying IDs, they go through a virtual checklist: taking a look at the mentioned security features one by one. Some features are easy to verify, some are not. Some can be verified just by touching and tilting the document or looking closely at it, while others require special equipment.

First-line verification

The so-called first-line verification is basically a list of checks that are performed quickly (within a few seconds) and it verifies the document’s genuineness with relatively high confidence. This is usually done automatically by passport reader devices, or manually by the border control personnel – the common factor is the speed and the high probability of detecting falsification.

If there is nothing extraordinary found, the check gets completed and the passport holder can move on.

first-line verification at the airport
first-line verification at an airport

When the first-line authentication is carried out by ID scanner devices, the following features are verified:

  • Printed data: the MRZ (Machine Readable Zone) standardized code lines – according to the ICAO9303 standard – are extracted and the system automatically verifies the security hash numbers, while it checks the document’s expiry date as well.
  • Ink: the so-called B900 ink check is performed using infrared illumination. The passport inspection system detects whether the data is printed with the appropriate ink type.
  • Paper material: also called UV dullness check, the device checks the response of the paper under UV illumination – to confirm if the document is printed on security paper (also called UV-dull paper).
  • Digital data: if the document is equipped with an RFID chip and the inspection system has the capability of reading it, the digital content is also being verified. The terminal establishes a secure communication channel and extracts the digital chip content – which then can be cross-checked with the printed data.

Second-line verification

Also called second-line checks, it takes a remarkably long time and requires special equipment and expert knowledge of identity documents. The second line checks usually come into the picture if an ID fails at the first line checks or the system detects some kind of alert, therefore it has to be analyzed in an even more detailed way: either using special wavelengths of illuminations or applying high magnification using a microscope.

Wikipedia, Border checkpoint

“Second-line check” means a further check which may be carried out in a special location away from the location at which all persons are checked (first line)*

* Source:

There is special equipment available for this purpose: devices that include more types of illuminations sources than the compact passport readers, and also include high optical zoom to check delicate background graphics, microprints, etc. This type of equipment is large, heavy, and expensive – used only by specialists.

second-line passport inspection system
inside a typical second-line passport inspection system

Our scope in ID verification

At Adaptive Recognition, we develop technology for maximizing the potential of first-line verification checks – that’s what our passport readers have done perfectly for decades, in border control systems, but not only there, also in banks, casinos, and a wide range of front-office applications where ID checks are crucial.

View our first-line scanners


Our latest first-line verification device is called Osmond. However, it is not purely a first-line model – it has some extra features that position it almost in the second line class (like its unique edge light feature, or the high resolution that lets you check even some types of microprints). Discover this new innovation →

first-line verification checks
maximizing the potential of first-line verification checks

Learn more about first-line checks in these projects

Recently, we have been involved in two first-line check projects, both carried out with ABC (Automated Border Control) e-gates. Our passport readers are integrated in these automatic gates, playing an important role in automatically scanning and verifying the document. The retrieved face photograph is even compared with the live face portrait of the traveler.

Read the following case studies:

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