What is commonly called a QR code comes from the English term Quick Response Barcode and means a barcode that responds quickly. Anyone who has ever tried it have realized the speed with which a reader is able to recognize a code of this type.
Like so many other technology products, QR codes have also made their way into education,  using the curiosity they generate, the large amount and variety of information with which they can connect such as images, texts, videos, web pages, etc., and its universal condition; thanks to the fact that today it can be read by almost any mobile phone. Added to these advantages is the fact that the use of QR codes is free, license-free  and also can work even without internet access within a closed network that contains the material loaded in the code.  Simply put, QR codes in education allow access to almost any information quickly and in a direct, clear, concise, secure and timely manner. 
One of the most common applications of these codes in education is associated with libraries. They are linked to virtual books or audiovisual materials to broaden and diversify the student's experience, while facilitating access to information that they would not have known using more traditional navigation methods.  A direct example of this experience is the organization of games like “treasure hunt” where students find codes that reveal more clues.  In a study carried out in some Colombian libraries it was found that 81% of the surveyed population was in favor of the use of this technology in their libraries, while the remaining 19% is indifferent to its use. [ 3] Another study showed that 83% of the student experienced less stress when they studied the lessons with the help of QR codes thanks to the fact that they could easily find the correct information. 
But the application possibilities are wide. To point out two specific and recent examples, the following is an experience from the United Arab Emirates and another from the United States of America.
In university institutions in the United Arab Emirates, where all students had mobile phones capable of reading QR codes, Ali, Santos and Areepattamannil  used QR codes to construct various questionnaires in 2017. In this experience they also involved a significant number of teachers in training to familiarize themselves with the tool and contribute to broadening the study. In this experiment, a series of questionnaires were developed where each question had a code that led to the information necessary to answer. After facing these exercises, most of the students felt that the codes facilitated access to web pages, were quick and easy to read, and could also be used very easily.
Another interesting example was designed by Sánchez-Azqueta, Cascarosa, Celma, Gimeno and Aldea around a course related to electronics and they made it known in 2020.  In this case, some of the codes were printed and pasted directly onto the tools in the lab, leading to information on their use and the full manual. Other codes were included in the printed documentation used in the workshop sessions to connect to multimedia material and additional information. In this experience, QR codes facilitated the review of manuals and measurement processes, improved the time required to carry out activities, and diversified the available resources.
For the implementation of QR codes in the classroom it is important to attend to the following recommendations: 
Check that student devices can scan QR codes.
Create codes to be used both inside and outside the classroom for.
Encourage students to create their own codes.
Train teachers in the use of QR codes.
QR codes have been in use for years, but they are becoming more and more popular in education. Although it is necessary that all students have devices to be able to interact with them (or perhaps organize group activities or similar), they are an interesting tool that can attract the attention of the participants in the course and connect with a great variety and diversity of materials and information.
 V. Yfantis, P. Kalagiakos, C. Kouloumperi, y P. Karampelas, «Quick response codes in E-learning», presentado en 2016 International Conference on Advances in Computing, Communications and Informatics (ICACCI), sep. 2016, doi: 10.1109/ICACCI.2016.7732198.
 E. Quintero, N. A. Arias, J. P. P. Giraldo, y J. Bermúdez-Hernández, «Estrategias para la Implementación de los Códigos Bidimensionales Quick Response (QR) en las Bibliotecas Universitarias», Rev. CIES Escolme, vol. 10, n.o 2, Art. n.o 2, ago. 2019.
 S. Goyal, S. Yadav, y M. Mathuria, «Exploring concept of QR code and its benefits in digital education system», en 2016 International Conference on Advances in Computing, Communications and Informatics (ICACCI), sep. 2016, pp. 1141-1147, doi: 10.1109/ICACCI.2016.7732198.
 N. Ali, I. M. Santos, y S. Areepattamannil, «Pre-Service Teachers’ Perception of Quick Response (QR) Code Integration in Classroom Activities», Turk. Online J. Educ. Technol. - TOJET, vol. 16, n.o 1, pp. 93-100, ene. 2017.
 C. Sánchez-Azqueta, E. Cascarosa, S. Celma, C. Gimeno, y C. Aldea, «Quick response codes as a complement for the teaching of Electronics in laboratory activities», Int. J. Electr. Eng. Educ., abr. 2020, doi: 10.1177/0020720920916431.