# Character Substitution Performs a random character replacement that preserves formatting (spaces, capitalization, and punctuation). Characters are replaced with other characters from within the same Unicode Block. A given source character is always mapped to the same destination character. For example, `M` might always map to `V`. For example, for the following input string: `Miami Store #162` The output would be something like: `Vgkjg Gmlvf #681` Note that for a numeric column, when a generated number starts with a 0, the starting 0 is removed. This could result in matching output values in different columns. For example, one column is changed to 113 and the other to 0113, which also becomes 113. Character Substitution is similar to [Character Scramble](https://docs.tonic.ai/app/generation/generators/generator-reference/character-scramble), with a couple of key differences. Because Character Substitution always maps the same source character to the same destination character, it is always consistent. It also can be used for unique columns. In Character Scramble, the character mapping is random, which makes Character Scramble slightly more secure. However, Character Scramble cannot be used for unique columns. ## Characteristics


Consistency	This generator is implicitly self-consistent. You do not specify whether the generator is consistent. Every occurrence of a character always maps to the same substitute character. Because of this, it can be used to preserve a join between two text columns, such as a join on a name or email.
Linking	No, cannot be linked.
Differential privacy	No
Data-free	No
Allowed for primary keys	Yes
Allowed for unique columns	Yes
Uses format-preserving encryption (FPE)	No
Privacy ranking	4
Generator ID (for the API)	`StringMaskGenerator`

## How to configure If [Structural data encryption](https://docs.tonic.ai/app/generation/generators-assign-config/generators-data-encryption-config) is enabled, then to use it for this column, in the advanced options section, toggle **Use data encryption process** to the on position.