Common indicators utilized in titrations include phenolphthalein, bromothymol blue, methyl orange, and litmus.

In a titration, an indicator serves to signal the endpoint of the reaction. This endpoint is reached when the amount of reactant in the solution is precisely sufficient to completely react with the other substance. The selection of an appropriate indicator is contingent upon the characteristics of the reaction and the pH at the equivalence point.

Phenolphthalein is a widely used indicator in titrations. It appears colorless in acidic solutions and turns pink in alkaline solutions, making it particularly suitable for strong acid-strong base titrations, where the pH undergoes a rapid change around the equivalence point.

Bromothymol blue is another frequently employed indicator. It transitions from yellow to blue as the solution shifts from acidic to alkaline. This indicator is often used in weak acid-strong base titrations, where the pH at the equivalence point exceeds $7$.

Methyl orange is an indicator that changes from red in acidic solutions to yellow in alkaline solutions. It is typically utilized in strong acid-weak base titrations, where the pH at the equivalence point is less than $7$.

Litmus is a straightforward indicator that shifts from red in acidic solutions to blue in alkaline solutions. While it may not be as precise as the other indicators, it is commonly employed in teaching laboratories to illustrate the concept of acid-base reactions.

In summary, the choice of indicator in a titration is influenced by the nature of the reaction and the pH at the equivalence point. The most commonly utilized indicators are phenolphthalein, bromothymol blue, methyl orange, and litmus.