Copper-catalyzed azide–alkyne cycloaddition (CuAAC) is a widely used and reliable method for forming covalent bonds between molecules containing various functional groups. It has been applied in organic synthesis, medicinal chemistry, surface chemistry, and bioconjugation. Despite its simplicity, the reaction involves complex mechanisms with multiple reversible steps involving copper(I) acetylides. Understanding these equilibria is crucial for controlling the reaction's catalytic cycle. This review discusses the history, key mechanisms, and applications of CuAAC, highlighting its utility across different chemical fields. CuAAC, a form of click chemistry, is known for its high yield, ease of use, and compatibility with various conditions. It converts organic azides and terminal alkynes into 1,4-disubstituted 1,2,3-triazoles. The reaction is highly efficient, with a rate increase of 10^7 compared to thermal processes. It is not significantly affected by the steric or electronic properties of the groups involved, making it versatile for various substrates. The 1,2,3-triazole heterocycle is chemically stable, has a strong dipole moment, and can interact with biological molecules and surfaces. Other metals, such as ruthenium, have been explored for similar reactions, but CuAAC remains the only metal that reliably catalyzes the reaction. The reaction is robust, compatible with many functional groups, and can be performed in aqueous or organic solvents. Various catalysts and ligands have been tested, with some showing high catalytic activity. The reaction is particularly useful for synthesizing complex molecules, including those with multiple functional groups. The mechanism of CuAAC involves the formation of a copper(I) acetylide intermediate, which reacts with the azide to form a triazole. The reaction is highly efficient and can be performed under mild conditions. The use of ascorbate as a reducing agent has been shown to be effective in aqueous conditions. The reaction can also be catalyzed by elemental copper, simplifying the process. CuAAC has been applied in the synthesis of various compounds, including triazoles, and has been used in the development of new chemical transformations. The reaction is particularly useful for the synthesis of complex molecules, including those with multiple functional groups. The reaction is highly efficient and can be performed under mild conditions, making it a valuable tool in chemical synthesis. The reaction is also useful in the synthesis of biologically active compounds, including those with multiple functional groups. The reaction is highly efficient and can be performed under mild conditions, making it a valuable tool in chemical synthesis.Copper-catalyzed azide–alkyne cycloaddition (CuAAC) is a widely used and reliable method for forming covalent bonds between molecules containing various functional groups. It has been applied in organic synthesis, medicinal chemistry, surface chemistry, and bioconjugation. Despite its simplicity, the reaction involves complex mechanisms with multiple reversible steps involving copper(I) acetylides. Understanding these equilibria is crucial for controlling the reaction's catalytic cycle. This review discusses the history, key mechanisms, and applications of CuAAC, highlighting its utility across different chemical fields. CuAAC, a form of click chemistry, is known for its high yield, ease of use, and compatibility with various conditions. It converts organic azides and terminal alkynes into 1,4-disubstituted 1,2,3-triazoles. The reaction is highly efficient, with a rate increase of 10^7 compared to thermal processes. It is not significantly affected by the steric or electronic properties of the groups involved, making it versatile for various substrates. The 1,2,3-triazole heterocycle is chemically stable, has a strong dipole moment, and can interact with biological molecules and surfaces. Other metals, such as ruthenium, have been explored for similar reactions, but CuAAC remains the only metal that reliably catalyzes the reaction. The reaction is robust, compatible with many functional groups, and can be performed in aqueous or organic solvents. Various catalysts and ligands have been tested, with some showing high catalytic activity. The reaction is particularly useful for synthesizing complex molecules, including those with multiple functional groups. The mechanism of CuAAC involves the formation of a copper(I) acetylide intermediate, which reacts with the azide to form a triazole. The reaction is highly efficient and can be performed under mild conditions. The use of ascorbate as a reducing agent has been shown to be effective in aqueous conditions. The reaction can also be catalyzed by elemental copper, simplifying the process. CuAAC has been applied in the synthesis of various compounds, including triazoles, and has been used in the development of new chemical transformations. The reaction is particularly useful for the synthesis of complex molecules, including those with multiple functional groups. The reaction is highly efficient and can be performed under mild conditions, making it a valuable tool in chemical synthesis. The reaction is also useful in the synthesis of biologically active compounds, including those with multiple functional groups. The reaction is highly efficient and can be performed under mild conditions, making it a valuable tool in chemical synthesis.