The group of dyestuffs known as direct dyes is applied directly to the substrate in an alkaline or neutral solution. They can be applied to silk, wool, or rayon and produce entire shapes without the need for mordanting on cotton, linen, or other fabrics. Bright colors are produced by direct dyes, however, the wash is subpar.

Direct dyes are pigments that cling to their surfaces through non-ionic forces, typically textiles. Its strength is measured in terms of substantivity, and the higher it is, the more alluring the dye is to the fiber. Cellulosic fibers have a strong affinity for direct dyes, hence neutral or mildly basic solutions should be used when dying them. Most sodium salts of aromatic chemicals are used to make direct dyes. They are soluble in water, and as the temperature rises, so does their solubility. In water, direct dyes can separate into anions. Direct dyes can be divided into four groups based on their intended uses: general direct dyes, direct fast dyes, direct copper dyes, and direct diazo dyes.

These direct dyes can benefit from various after-treatments to increase their wash fastness, and they are referred to as after-treated direct colors. These are molecules that cling to the fabric molecules on their own, without the aid of any other substances. These are classified as anionic dyes that are merely applied from an aqueous dye solution containing sodium chloride or sodium sulfate and an electrolyte and that have substantial cellulose fibers.

In order to improve wet fastness, which has been required for the majority of direct dyeing, direct dye is the method that is carried out in a slightly alkaline dye bath at or near the boiling point. This process has a separate treatment called cationic dye fixing.

Wool, leather, paper, silk, cotton, and nylon can all benefit from direct dyeing. They are also helpful as biological stains and pH monitors. The paper industry has been utilizing various colors for hundreds of years. It is realistic to predict that dyes for the paper industry have a bright future given the expansion of the paper sector. Direct cationic dyes and sulfur dyes are among the useful dyes. In addition to these two choices, acid dyes and basic dyes can be helpful.