The weakest hair developer typically has a lower percentage of hydrogen peroxide.
Hydrogen peroxide is the key ingredient in hair developers, and its concentration determines the strength of the developer.
Lower percentages of hydrogen peroxide, such as 1.5% or 2%, are considered weakest and are used for subtle, gradual color changes or for toning purposes.
These weaker developers are often preferred for sensitive scalps or for individuals who want to achieve a more natural-looking color result.
Remember that the strength of the developer should always be matched with the desired level of lift or color change.
